From 188b578c0e9995c864d284f22de4e48c220b0596 Mon Sep 17 00:00:00 2001
From: mstaib <mstaib@google.com>
Date: Wed, 16 May 2018 10:13:51 -0700
Subject: Enable manual trimming of config_feature_flags.

This enables users of config_feature_flags to specify the flags used by the transitive closure of a particular target in the transitive_configs attribute of all targets. It also adds a flag - --enforce_transitive_configs_for_config_feature_flag - which enforces this specification and uses it to trim the set of flags available to that target.

RELNOTES: None.
PiperOrigin-RevId: 196846092
---
 .../android/AbstractAndroidLocalTestTestBase.java  |  58 +-
 .../build/lib/rules/android/AndroidBinaryTest.java |  70 +-
 .../config/ConfigFeatureFlagConfigurationTest.java |  48 +-
 .../lib/rules/config/ConfigFeatureFlagTest.java    |  13 +-
 .../build/lib/rules/config/ConfigSettingTest.java  | 122 +++-
 .../config/FeatureFlagManualTrimmingTest.java      | 770 +++++++++++++++++++++
 .../build/lib/rules/objc/AppleBinaryTest.java      |  10 +-
 .../lib/rules/objc/AppleStaticLibraryTest.java     |  10 +-
 .../build/lib/rules/objc/ObjcRuleTestCase.java     |   3 +
 .../build/lib/skylark/SkylarkRuleContextTest.java  |   1 +
 10 files changed, 1046 insertions(+), 59 deletions(-)
 create mode 100644 src/test/java/com/google/devtools/build/lib/rules/config/FeatureFlagManualTrimmingTest.java

(limited to 'src/test/java/com/google/devtools/build/lib')

diff --git a/src/test/java/com/google/devtools/build/lib/rules/android/AbstractAndroidLocalTestTestBase.java b/src/test/java/com/google/devtools/build/lib/rules/android/AbstractAndroidLocalTestTestBase.java
index 301d2acc12..bf62f4f71c 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/android/AbstractAndroidLocalTestTestBase.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/android/AbstractAndroidLocalTestTestBase.java
@@ -93,7 +93,9 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
 
   @Test
   public void testFeatureFlagsAttributeSetsSelectInDependency() throws Exception {
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
     writeFile(
         "java/com/foo/BUILD",
         "load('//java/bar:foo.bzl', 'extra_deps')",
@@ -105,6 +107,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "config_feature_flag(",
         "  name = 'flag2',",
@@ -114,6 +117,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "config_setting(",
         "  name = 'flag2@on',",
         "  flag_values = {':flag2': 'on'},",
+        "  transitive_configs = [':flag2'],",
         ")",
         "android_library(",
         "  name = 'lib',",
@@ -124,6 +128,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "    ':flag2@on': ['Flag2On.java'],",
         "    '//conditions:default': ['Flag2Off.java'],",
         "  }),",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")",
         "android_local_test(",
         "  name = 'foo',",
@@ -131,7 +136,8 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "  deps = [':lib'] + extra_deps,",
         "  feature_flags = {",
         "    'flag1': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")");
     ConfiguredTarget binary = getConfiguredTarget("//java/com/foo");
     List<String> inputs =
@@ -144,7 +150,9 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
 
   @Test
   public void testFeatureFlagsAttributeSetsSelectInTest() throws Exception {
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
     writeFile(
         "java/com/foo/BUILD",
         "load('//java/bar:foo.bzl', 'extra_deps')",
@@ -156,6 +164,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "config_feature_flag(",
         "  name = 'flag2',",
@@ -165,6 +174,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "config_setting(",
         "  name = 'flag2@on',",
         "  flag_values = {':flag2': 'on'},",
+        "  transitive_configs = [':flag2'],",
         ")",
         "android_local_test(",
         "  name = 'foo',",
@@ -178,7 +188,8 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "  }),",
         "  feature_flags = {",
         "    'flag1': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")");
     ConfiguredTarget binary = getConfiguredTarget("//java/com/foo");
     List<String> inputs =
@@ -192,7 +203,9 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
   @Test
   public void testFeatureFlagsAttributeFailsAnalysisIfFlagValueIsInvalid() throws Exception {
     reporter.removeHandler(failFastHandler);
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
     writeFile(
         "java/com/foo/BUILD",
         "load('//java/bar:foo.bzl', 'extra_deps')",
@@ -204,13 +217,15 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "android_library(",
         "  name = 'lib',",
         "  srcs = select({",
         "    ':flag1@on': ['Flag1On.java'],",
         "    '//conditions:default': ['Flag1Off.java'],",
-        "  })",
+        "  }),",
+        "  transitive_configs = [':flag1'],",
         ")",
         "android_local_test(",
         "  name = 'foo',",
@@ -218,7 +233,8 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "  deps = [':lib',] + extra_deps,",
         "  feature_flags = {",
         "    'flag1': 'invalid',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/foo")).isNull();
     assertContainsEvent(
@@ -230,7 +246,9 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
   public void testFeatureFlagsAttributeFailsAnalysisIfFlagValueIsInvalidEvenIfNotUsed()
       throws Exception {
     reporter.removeHandler(failFastHandler);
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
     writeFile(
         "java/com/foo/BUILD",
         "load('//java/bar:foo.bzl', 'extra_deps')",
@@ -259,7 +277,9 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
 
   @Test
   public void testFeatureFlagsAttributeSetsFeatureFlagProviderValues() throws Exception {
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
     writeFile(
         "java/com/foo/reader.bzl",
         "def _impl(ctx):",
@@ -291,6 +311,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "flag_reader(",
         "  name = 'FooFlags',",
         "  flags = [':flag1', ':flag2'],",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")",
         "android_local_test(",
         "  name = 'foo',",
@@ -298,7 +319,8 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "  deps = extra_deps,",
         "  feature_flags = {",
         "    'flag1': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")");
     Artifact flagList =
         actionsTestUtil().getFirstArtifactEndingWith(
@@ -314,7 +336,9 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
   public void testFeatureFlagsAttributeFailsAnalysisIfFlagIsAliased()
       throws Exception {
     reporter.removeHandler(failFastHandler);
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
     writeFile(
         "java/com/foo/BUILD",
         "load('//java/bar:foo.bzl', 'extra_deps')",
@@ -326,6 +350,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "alias(",
         "  name = 'alias',",
         "  actual = 'flag1',",
+        "  transitive_configs = [':flag1'],",
         ")",
         "android_local_test(",
         "  name = 'foo',",
@@ -333,7 +358,8 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "  deps = extra_deps,",
         "  feature_flags = {",
         "    'alias': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/foo")).isNull();
     assertContainsEvent(String.format(
@@ -345,6 +371,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
   @Test
   public void testFeatureFlagPolicyMustBeVisibleToRuleToUseFeatureFlags() throws Exception {
     reporter.removeHandler(failFastHandler); // expecting an error
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     overwriteFile(
         "tools/whitelists/config_feature_flag/BUILD",
         "package_group(",
@@ -367,7 +394,8 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "  deps = extra_deps,",
         "  feature_flags = {",
         "    '//flag:flag': 'right',",
-        "  }",
+        "  },",
+        "  transitive_configs = ['//flag:flag'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/google/android/foo:foo")).isNull();
     assertContainsEvent(
@@ -378,6 +406,7 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
 
   @Test
   public void testFeatureFlagPolicyDoesNotBlockRuleIfInPolicy() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     overwriteFile(
         "tools/whitelists/config_feature_flag/BUILD",
         "package_group(",
@@ -400,7 +429,8 @@ public abstract class AbstractAndroidLocalTestTestBase extends BuildViewTestCase
         "  deps = extra_deps,",
         "  feature_flags = {",
         "    '//flag:flag': 'right',",
-        "  }",
+        "  },",
+        "  transitive_configs = ['//flag:flag'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/google/android/foo:foo")).isNotNull();
     assertNoEvents();
diff --git a/src/test/java/com/google/devtools/build/lib/rules/android/AndroidBinaryTest.java b/src/test/java/com/google/devtools/build/lib/rules/android/AndroidBinaryTest.java
index 3a9bb90190..7d41301892 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/android/AndroidBinaryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/android/AndroidBinaryTest.java
@@ -3006,7 +3006,9 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
 
   @Test
   public void testFeatureFlagsAttributeSetsSelectInDependency() throws Exception {
-    useConfiguration("--experimental_dynamic_configs=notrim");
+    useConfiguration(
+        "--experimental_dynamic_configs=notrim",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "java/com/foo/BUILD",
         "config_feature_flag(",
@@ -3017,6 +3019,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "config_feature_flag(",
         "  name = 'flag2',",
@@ -3026,6 +3029,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "config_setting(",
         "  name = 'flag2@on',",
         "  flag_values = {':flag2': 'on'},",
+        "  transitive_configs = [':flag2'],",
         ")",
         "android_library(",
         "  name = 'lib',",
@@ -3036,6 +3040,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "    ':flag2@on': ['Flag2On.java'],",
         "    '//conditions:default': ['Flag2Off.java'],",
         "  }),",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")",
         "android_binary(",
         "  name = 'foo',",
@@ -3043,7 +3048,8 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "  deps = [':lib'],",
         "  feature_flags = {",
         "    'flag1': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")");
     ConfiguredTarget binary = getConfiguredTarget("//java/com/foo");
     List<String> inputs =
@@ -3055,7 +3061,9 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
 
   @Test
   public void testFeatureFlagsAttributeSetsSelectInBinary() throws Exception {
-    useConfiguration("--experimental_dynamic_configs=notrim");
+    useConfiguration(
+        "--experimental_dynamic_configs=notrim",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "java/com/foo/BUILD",
         "config_feature_flag(",
@@ -3066,6 +3074,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "config_feature_flag(",
         "  name = 'flag2',",
@@ -3075,6 +3084,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "config_setting(",
         "  name = 'flag2@on',",
         "  flag_values = {':flag2': 'on'},",
+        "  transitive_configs = [':flag2'],",
         ")",
         "android_binary(",
         "  name = 'foo',",
@@ -3088,7 +3098,8 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "  }),",
         "  feature_flags = {",
         "    'flag1': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")");
     ConfiguredTarget binary = getConfiguredTarget("//java/com/foo");
     List<String> inputs =
@@ -3100,7 +3111,9 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
 
   @Test
   public void testFeatureFlagsAttributeSetsSelectInBinaryAlias() throws Exception {
-    useConfiguration("--experimental_dynamic_configs=notrim");
+    useConfiguration(
+        "--experimental_dynamic_configs=notrim",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "java/com/foo/BUILD",
         "config_feature_flag(",
@@ -3111,6 +3124,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "android_binary(",
         "  name = 'foo',",
@@ -3121,7 +3135,8 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "  }),",
         "  feature_flags = {",
         "    'flag1': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1'],",
         ")",
         "alias(",
         "  name = 'alias',",
@@ -3138,7 +3153,9 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
   @Test
   public void testFeatureFlagsAttributeFailsAnalysisIfFlagValueIsInvalid() throws Exception {
     reporter.removeHandler(failFastHandler);
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "java/com/foo/BUILD",
         "config_feature_flag(",
@@ -3149,13 +3166,15 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "android_library(",
         "  name = 'lib',",
         "  srcs = select({",
         "    ':flag1@on': ['Flag1On.java'],",
         "    '//conditions:default': ['Flag1Off.java'],",
-        "  })",
+        "  }),",
+        "  transitive_configs = [':flag1'],",
         ")",
         "android_binary(",
         "  name = 'foo',",
@@ -3163,7 +3182,8 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "  deps = [':lib'],",
         "  feature_flags = {",
         "    'flag1': 'invalid',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/foo")).isNull();
     assertContainsEvent(
@@ -3175,7 +3195,9 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
   public void testFeatureFlagsAttributeFailsAnalysisIfFlagValueIsInvalidEvenIfNotUsed()
       throws Exception {
     reporter.removeHandler(failFastHandler);
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "java/com/foo/BUILD",
         "config_feature_flag(",
@@ -3186,13 +3208,15 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "android_binary(",
         "  name = 'foo',",
         "  manifest = 'AndroidManifest.xml',",
         "  feature_flags = {",
         "    'flag1': 'invalid',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/foo")).isNull();
     assertContainsEvent(
@@ -3204,7 +3228,9 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
   public void testFeatureFlagsAttributeFailsAnalysisIfFlagIsAliased()
       throws Exception {
     reporter.removeHandler(failFastHandler);
-    useConfiguration("--experimental_dynamic_configs=notrim");
+    useConfiguration(
+        "--experimental_dynamic_configs=notrim",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "java/com/foo/BUILD",
         "config_feature_flag(",
@@ -3215,13 +3241,15 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "alias(",
         "  name = 'alias',",
         "  actual = 'flag1',",
+        "  transitive_configs = [':flag1'],",
         ")",
         "android_binary(",
         "  name = 'foo',",
         "  manifest = 'AndroidManifest.xml',",
         "  feature_flags = {",
         "    'alias': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/foo")).isNull();
     assertContainsEvent(
@@ -3232,7 +3260,9 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
 
   @Test
   public void testFeatureFlagsAttributeSetsFeatureFlagProviderValues() throws Exception {
-    useConfiguration("--experimental_dynamic_configs=notrim");
+    useConfiguration(
+        "--experimental_dynamic_configs=notrim",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "java/com/foo/reader.bzl",
         "def _impl(ctx):",
@@ -3263,6 +3293,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "flag_reader(",
         "  name = 'FooFlags',",
         "  flags = [':flag1', ':flag2'],",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")",
         "android_binary(",
         "  name = 'foo',",
@@ -3270,7 +3301,8 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "  srcs = [':FooFlags.java'],",
         "  feature_flags = {",
         "    'flag1': 'on',",
-        "  }",
+        "  },",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")");
     Artifact flagList =
         getFirstArtifactEndingWith(
@@ -3316,6 +3348,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
   @Test
   public void testFeatureFlagPolicyMustContainRuleToUseFeatureFlags() throws Exception {
     reporter.removeHandler(failFastHandler); // expecting an error
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratch.overwriteFile(
         "tools/whitelists/config_feature_flag/BUILD",
         "package_group(",
@@ -3337,7 +3370,8 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "  srcs = [':FooFlags.java'],",
         "  feature_flags = {",
         "    '//flag:flag': 'right',",
-        "  }",
+        "  },",
+        "  transitive_configs = ['//flag:flag'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/google/android/foo:foo")).isNull();
     assertContainsEvent(
@@ -3348,6 +3382,7 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
 
   @Test
   public void testFeatureFlagPolicyDoesNotBlockRuleIfInPolicy() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratch.overwriteFile(
         "tools/whitelists/config_feature_flag/BUILD",
         "package_group(",
@@ -3369,7 +3404,8 @@ public class AndroidBinaryTest extends AndroidBuildViewTestCase {
         "  srcs = [':FooFlags.java'],",
         "  feature_flags = {",
         "    '//flag:flag': 'right',",
-        "  }",
+        "  },",
+        "  transitive_configs = ['//flag:flag'],",
         ")");
     assertThat(getConfiguredTarget("//java/com/google/android/foo:foo")).isNotNull();
     assertNoEvents();
diff --git a/src/test/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagConfigurationTest.java b/src/test/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagConfigurationTest.java
index 07dcae5dc2..7811335294 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagConfigurationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagConfigurationTest.java
@@ -16,12 +16,15 @@ package com.google.devtools.build.lib.rules.config;
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth8.assertThat;
+import static org.junit.Assert.fail;
 
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.actions.util.LabelArtifactOwner;
 import com.google.devtools.build.lib.cmdline.Label;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -40,13 +43,39 @@ public final class ConfigFeatureFlagConfigurationTest {
   }
 
   @Test
-  public void getFeatureFlagValue_returnsEmptyOptionalWhenRequestingUnsetFlag() throws Exception {
+  public void
+      getFeatureFlagValue_returnsEmptyOptionalWhenRequestingUnknownFlagFromUntrimmedOptions()
+          throws Exception {
     Optional<String> flagValue =
-        getConfigurationWithFlags(ImmutableMap.of(Label.parseAbsoluteUnchecked("//a:a"), "valued"))
+        getUntrimmedConfigurationWithFlags(
+                ImmutableMap.of(Label.parseAbsoluteUnchecked("//a:a"), "valued"))
             .getFeatureFlagValue(new LabelArtifactOwner(Label.parseAbsoluteUnchecked("//b:b")));
     assertThat(flagValue).isEmpty();
   }
 
+  @Test
+  public void getFeatureFlagValue_returnsEmptyOptionalWhenRequestingKnownDefaultFlag()
+      throws Exception {
+    Optional<String> flagValue =
+        getConfigurationWithFlags(
+                ImmutableMap.of(Label.parseAbsoluteUnchecked("//a:a"), "valued"),
+                ImmutableSet.of(
+                    Label.parseAbsoluteUnchecked("//a:a"), Label.parseAbsoluteUnchecked("//b:b")))
+            .getFeatureFlagValue(new LabelArtifactOwner(Label.parseAbsoluteUnchecked("//b:b")));
+    assertThat(flagValue).isEmpty();
+  }
+
+  @Test
+  public void getFeatureFlagValue_throwsExceptionWhenRequestingUnknownFlag() throws Exception {
+    try {
+      getConfigurationWithFlags(ImmutableMap.of(Label.parseAbsoluteUnchecked("//a:a"), "valued"))
+          .getFeatureFlagValue(new LabelArtifactOwner(Label.parseAbsoluteUnchecked("//b:b")));
+      fail("no exception was thrown");
+    } catch (ConfigFeatureFlagConfiguration.MissingFlagException expected) {
+      assertThat(expected).hasMessageThat().contains("//b:b");
+    }
+  }
+
   @Test
   public void getOutputDirectoryName_returnsNullWhenFlagMapIsEmpty() throws Exception {
     assertThat(getConfigurationWithFlags(ImmutableMap.<Label, String>of()).getOutputDirectoryName())
@@ -133,7 +162,22 @@ public final class ConfigFeatureFlagConfigurationTest {
   /** Generates a configuration fragment with the given set of flag-value pairs. */
   private static ConfigFeatureFlagConfiguration getConfigurationWithFlags(
       Map<Label, String> flags) {
+    return getConfigurationWithFlags(flags, flags.keySet());
+  }
+
+  private static ConfigFeatureFlagConfiguration getConfigurationWithFlags(
+      Map<Label, String> flags, Set<Label> availableFlags) {
+    ConfigFeatureFlagOptions options = new ConfigFeatureFlagOptions();
+    options.enforceTransitiveConfigsForConfigFeatureFlag = true;
+    options.replaceFlagValues(flags);
+    options.trimFlagValues(availableFlags);
+    return new ConfigFeatureFlagConfiguration(options);
+  }
+
+  private static ConfigFeatureFlagConfiguration getUntrimmedConfigurationWithFlags(
+      Map<Label, String> flags) {
     ConfigFeatureFlagOptions options = new ConfigFeatureFlagOptions();
+    options.enforceTransitiveConfigsForConfigFeatureFlag = false;
     options.replaceFlagValues(flags);
     return new ConfigFeatureFlagConfiguration(options);
   }
diff --git a/src/test/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagTest.java b/src/test/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagTest.java
index 411294abbd..e9861dfc66 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/config/ConfigFeatureFlagTest.java
@@ -38,7 +38,9 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
 
   @Before
   public void useTrimmedConfigurations() throws Exception {
-    useConfiguration("--experimental_dynamic_configs=on");
+    useConfiguration(
+        "--experimental_dynamic_configs=on",
+        "--enforce_transitive_configs_for_config_feature_flag");
   }
 
   @Override
@@ -72,6 +74,7 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
         "    flag_values = {",
         "        ':flag': 'configured',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -91,6 +94,7 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
         "    flag_values = {",
         "        ':flag': 'configured',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -157,10 +161,12 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
         "    flag_values = {",
         "        ':flag': 'configured',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "flag_reading_wrapper(",
         "    name = 'wrapper',",
         "    flag = ':flag',",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -215,6 +221,7 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
         "flag_reading_wrapper(",
         "    name = 'wrapper',",
         "    flag = ':flag',",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -253,6 +260,7 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
         "    flag_values = {",
         "        ':other': 'configured',",
         "    },",
+        "    transitive_configs = [':flag', ':other'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -280,6 +288,7 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
         "    flag_values = {",
         "        ':other': 'configured',",
         "    },",
+        "    transitive_configs = [':flag', ':other'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -339,6 +348,7 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
         "    flag_values = {",
         "        ':flag': 'legal',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -362,6 +372,7 @@ public final class ConfigFeatureFlagTest extends SkylarkTestCase {
         "    flag_values = {",
         "        ':flag': 'invalid',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
diff --git a/src/test/java/com/google/devtools/build/lib/rules/config/ConfigSettingTest.java b/src/test/java/com/google/devtools/build/lib/rules/config/ConfigSettingTest.java
index 8faf64d8e4..46042fdce3 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/config/ConfigSettingTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/config/ConfigSettingTest.java
@@ -399,7 +399,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void matchesIfFlagValuesAndValuesBothMatch() throws Exception {
-    useConfiguration("--copt=-Dright");
+    useConfiguration("--copt=-Dright", "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -410,6 +410,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dright',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -421,6 +422,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void matchesIfFlagValuesMatchAndValuesAreEmpty() throws Exception {
+    useConfiguration("--copt=-Dright", "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -429,6 +431,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        ':flag': 'right',",
         "    },",
         "    values = {},",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -455,7 +458,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotMatchIfNeitherFlagValuesNorValuesMatches() throws Exception {
-    useConfiguration("--copt=-Dright");
+    useConfiguration("--copt=-Dright", "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -466,6 +469,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dwrong',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -477,6 +481,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotMatchIfFlagValuesDoNotMatchAndValuesAreEmpty() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -485,6 +490,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        ':flag': 'wrong',",
         "    },",
         "    values = {},",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -496,7 +502,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotMatchIfFlagValuesDoNotMatchButValuesDo() throws Exception {
-    useConfiguration("--copt=-Dright");
+    useConfiguration("--copt=-Dright", "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -507,6 +513,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dright',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -533,7 +540,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotMatchIfValuesDoNotMatchButFlagValuesDo() throws Exception {
-    useConfiguration("--copt=-Dright");
+    useConfiguration("--copt=-Dright", "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -544,6 +551,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dwrong',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -555,6 +563,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotMatchIfEvenOneFlagValueDoesNotMatch() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -564,6 +573,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        ':flag2': 'bad',",
         "    },",
         "    values = {},",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -580,12 +590,14 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void matchesIfNonDefaultIsSpecifiedAndFlagValueIsThatValue() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "feature_flag_setter(",
         "    name = 'setter',",
         "    exports_setting = ':match',",
         "    flag_values = {':flag': 'actual'},",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_setting(",
         "    name = 'match',",
@@ -593,6 +605,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        ':flag': 'actual',",
         "    },",
         "    values = {},",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -604,12 +617,14 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotMatchIfDefaultIsSpecifiedAndFlagValueIsNotDefault() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "feature_flag_setter(",
         "    name = 'setter',",
         "    exports_setting = ':match',",
         "    flag_values = {':flag': 'actual'},",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_setting(",
         "    name = 'match',",
@@ -617,6 +632,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        ':flag': 'default',",
         "    },",
         "    values = {},",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -628,7 +644,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotRefineSettingWithSameValuesAndSameFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -641,6 +660,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -652,6 +672,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -671,7 +692,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotRefineSettingWithDifferentValuesAndSameFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -683,6 +707,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -693,6 +718,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dright',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -712,7 +738,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotRefineSettingWithSameValuesAndDifferentFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -724,6 +753,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -734,6 +764,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag2'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -753,7 +784,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotRefineSettingWithDifferentValuesAndDifferentFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -764,6 +798,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dright',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -773,6 +808,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag2'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -792,7 +828,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotRefineSettingWithDifferentValuesAndSubsetFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -804,6 +843,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dright',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -813,6 +853,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -832,7 +873,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void doesNotRefineSettingWithSubsetValuesAndDifferentFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -844,6 +888,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -853,6 +898,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dright',",
         "    },",
+        "    transitive_configs = [':flag2'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -872,7 +918,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void refinesSettingWithSubsetValuesAndSameFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -885,6 +934,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -895,6 +945,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dright',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -914,7 +965,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void refinesSettingWithSameValuesAndSubsetFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -927,6 +981,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -937,6 +992,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -956,7 +1012,10 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void refinesSettingWithSubsetValuesAndSubsetFlagValues() throws Exception {
-    useConfiguration("--copt=-Dright", "--javacopt=-Dgood");
+    useConfiguration(
+        "--copt=-Dright",
+        "--javacopt=-Dgood",
+        "--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -969,6 +1028,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        'copt': '-Dright',",
         "        'javacopt': '-Dgood',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_setting(",
         "    name = 'other',",
@@ -978,6 +1038,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    values = {",
         "        'copt': '-Dright',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -997,6 +1058,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void matchesAliasedFlagsInFlagValues() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -1004,10 +1066,12 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "    flag_values = {",
         "        ':alias': 'right',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "alias(",
         "    name = 'alias',",
         "    actual = 'flag',",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -1019,6 +1083,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void aliasedFlagsAreCountedInRefining() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratch.file(
         "test/BUILD",
         "config_setting(",
@@ -1027,16 +1092,19 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        ':alias': 'right',",
         "        ':flag2': 'good',",
         "    },",
+        "    transitive_configs = [':flag', ':flag2'],",
         ")",
         "config_setting(",
         "    name = 'other',",
         "    flag_values = {",
         "        ':flag': 'right',",
         "    },",
+        "    transitive_configs = [':flag'],",
         ")",
         "alias(",
         "    name = 'alias',",
         "    actual = 'flag',",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
@@ -1056,6 +1124,7 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void referencingSameFlagViaMultipleAliasesFails() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     checkError(
         "test",
         "multialias",
@@ -1067,10 +1136,12 @@ public class ConfigSettingTest extends BuildViewTestCase {
         "        ':alias': 'right',",
         "        ':direct': 'right',",
         "    },",
+        "    transitive_configs = [':direct'],",
         ")",
         "alias(",
         "    name = 'alias',",
         "    actual = 'direct',",
+        "    transitive_configs = [':direct'],",
         ")",
         "config_feature_flag(",
         "    name = 'direct',",
@@ -1098,15 +1169,19 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void requiresValidValueForFlagValues() throws Exception {
-    checkError("test", "invalid_flag",
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
+    checkError(
+        "test",
+        "invalid_flag",
         "in flag_values attribute of config_setting rule //test:invalid_flag: "
-        + "error while parsing user-defined configuration values: "
-        + "'invalid' is not a valid value for '//test:flag'",
+            + "error while parsing user-defined configuration values: "
+            + "'invalid' is not a valid value for '//test:flag'",
         "config_setting(",
         "    name = 'invalid_flag',",
         "    flag_values = {",
         "        ':flag': 'invalid',",
-        "    })",
+        "    },",
+        "    transitive_configs = [':flag'])",
         "config_feature_flag(",
         "    name = 'flag',",
         "    allowed_values = ['right', 'valid'],",
@@ -1116,18 +1191,23 @@ public class ConfigSettingTest extends BuildViewTestCase {
 
   @Test
   public void usesAliasLabelWhenReportingErrorInFlagValues() throws Exception {
-    checkError("test", "invalid_flag",
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
+    checkError(
+        "test",
+        "invalid_flag",
         "in flag_values attribute of config_setting rule //test:invalid_flag: "
-        + "error while parsing user-defined configuration values: "
-        + "'invalid' is not a valid value for '//test:alias'",
+            + "error while parsing user-defined configuration values: "
+            + "'invalid' is not a valid value for '//test:alias'",
         "config_setting(",
         "    name = 'invalid_flag',",
         "    flag_values = {",
         "        ':alias': 'invalid',",
-        "    })",
+        "    },",
+        "    transitive_configs = [':flag'])",
         "alias(",
         "    name = 'alias',",
         "    actual = ':flag',",
+        "    transitive_configs = [':flag'],",
         ")",
         "config_feature_flag(",
         "    name = 'flag',",
diff --git a/src/test/java/com/google/devtools/build/lib/rules/config/FeatureFlagManualTrimmingTest.java b/src/test/java/com/google/devtools/build/lib/rules/config/FeatureFlagManualTrimmingTest.java
new file mode 100644
index 0000000000..e433fb98bf
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/rules/config/FeatureFlagManualTrimmingTest.java
@@ -0,0 +1,770 @@
+// Copyright 2018 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License
+
+package com.google.devtools.build.lib.rules.config;
+
+import static com.google.common.collect.ImmutableSortedMap.toImmutableSortedMap;
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.base.Splitter;
+import com.google.common.collect.ImmutableSortedMap;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Ordering;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.RuleContext;
+import com.google.devtools.build.lib.analysis.actions.FileWriteAction;
+import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
+import com.google.devtools.build.lib.analysis.configuredtargets.RuleConfiguredTarget.Mode;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.skylark.util.SkylarkTestCase;
+import com.google.devtools.build.lib.testutil.TestRuleClassProvider;
+import java.util.Map;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for manual trimming of feature flags with the transitive_configs attribute. */
+@RunWith(JUnit4.class)
+public final class FeatureFlagManualTrimmingTest extends SkylarkTestCase {
+
+  @Before
+  public void enableManualTrimming() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
+  }
+
+  @Override
+  protected ConfiguredRuleClassProvider getRuleClassProvider() {
+    ConfiguredRuleClassProvider.Builder builder =
+        new ConfiguredRuleClassProvider.Builder().addRuleDefinition(new FeatureFlagSetterRule());
+    TestRuleClassProvider.addStandardRules(builder);
+    return builder.build();
+  }
+
+  @Before
+  public void setUpFlagReadingRule() throws Exception {
+    scratch.file(
+        "test/read_flags.bzl",
+        "def _read_flags_impl(ctx):",
+        "  ctx.actions.write(",
+        "    ctx.outputs.flagdict,",
+        "    '\\n'.join(['%s:::%s' % (dep.label, dep[config_common.FeatureFlagInfo].value)",
+        "                for dep in ctx.attr.flags]))",
+        "  return [DefaultInfo(files = depset([ctx.outputs.flagdict]))]",
+        "read_flags = rule(",
+        "  implementation = _read_flags_impl,",
+        "  attrs = {'flags': attr.label_list()},",
+        "  outputs = {'flagdict': '%{name}.flags'},",
+        ")");
+  }
+
+  @Before
+  public void setUpHostTransitionRule() throws Exception {
+    scratch.file(
+        "test/host_transition.bzl",
+        "def _host_transition_impl(ctx):",
+        "  files = depset(transitive = [src[DefaultInfo].files for src in ctx.attr.srcs])",
+        "  return [DefaultInfo(files = files)]",
+        "host_transition = rule(",
+        "  implementation = _host_transition_impl,",
+        "  attrs = {'srcs': attr.label_list(cfg='host')},",
+        ")");
+  }
+
+  private ImmutableSortedMap<Label, String> getFlagMapFromConfiguration(BuildConfiguration config) {
+    return config.getOptions().get(ConfigFeatureFlagOptions.class).getFlagValues();
+  }
+
+  private ImmutableSortedMap<Label, String> getFlagValuesFromOutputFile(Artifact flagDict) {
+    String fileContents =
+        ((FileWriteAction) getActionGraph().getGeneratingAction(flagDict)).getFileContents();
+    return Splitter.on('\n')
+        .withKeyValueSeparator(":::")
+        .split(fileContents)
+        .entrySet()
+        .stream()
+        .collect(
+            toImmutableSortedMap(
+                Ordering.natural(),
+                (entry) -> Label.parseAbsoluteUnchecked(entry.getKey()),
+                Map.Entry::getValue));
+  }
+
+  @Test
+  public void duplicateTargetsCreatedWithTrimmingDisabled() throws Exception {
+    useConfiguration("--noenforce_transitive_configs_for_config_feature_flag");
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'left',",
+        "    deps = [':common'],",
+        "    flag_values = {",
+        "        ':different_flag': 'left',",
+        "        ':common_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':common_flag'],",
+        ")",
+        "feature_flag_setter(",
+        "    name = 'right',",
+        "    deps = [':common'],",
+        "    flag_values = {",
+        "        ':different_flag': 'right',",
+        "        ':common_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':common_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'common',",
+        "    flags = [':common_flag'],",
+        "    transitive_configs = [':common_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'different_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")",
+        "config_feature_flag(",
+        "    name = 'common_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact leftFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:left")).toList());
+    Artifact rightFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:right")).toList());
+
+    assertThat(leftFlags).isNotEqualTo(rightFlags);
+  }
+
+  @Test
+  public void featureFlagSetAndInTransitiveConfigs_GetsSetValue() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':trimmed_flag': 'left',",
+        "        ':used_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':used_flag'],",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'trimmed_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact targetFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:target")).toList());
+
+    Label usedFlag = Label.parseAbsolute("//test:used_flag");
+    assertThat(getFlagValuesFromOutputFile(targetFlags)).containsEntry(usedFlag, "configured");
+  }
+
+  @Test
+  public void featureFlagSetButNotInTransitiveConfigs_IsTrimmedOutAndCollapsesDuplicates()
+      throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'left',",
+        "    deps = [':common'],",
+        "    flag_values = {",
+        "        ':different_flag': 'left',",
+        "        ':common_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':common_flag'],",
+        ")",
+        "feature_flag_setter(",
+        "    name = 'right',",
+        "    deps = [':common'],",
+        "    flag_values = {" ,
+        "        ':different_flag': 'right',",
+        "        ':common_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':common_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'common',",
+        "    flags = [':common_flag'],",
+        "    transitive_configs = [':common_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'different_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")",
+        "config_feature_flag(",
+        "    name = 'common_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact leftFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:left")).toList());
+    Artifact rightFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:right")).toList());
+
+    assertThat(leftFlags).isEqualTo(rightFlags);
+    assertThat(leftFlags.getArtifactOwner()).isEqualTo(rightFlags.getArtifactOwner());
+  }
+
+  @Test
+  public void featureFlagInTransitiveConfigsButNotSet_GetsDefaultValue() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':trimmed_flag': 'left',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':used_flag'],",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'trimmed_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact targetFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:target")).toList());
+
+    Label usedFlag = Label.parseAbsolute("//test:used_flag");
+    assertThat(getFlagValuesFromOutputFile(targetFlags)).containsEntry(usedFlag, "default");
+  }
+
+  @Test
+  public void featureFlagInTransitiveConfigsButNotInTransitiveClosure_IsWastefulButDoesNotError()
+      throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'left',",
+        "    deps = [':common'],",
+        "    flag_values = {",
+        "        ':different_flag': 'left',",
+        "        ':common_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':different_flag', ':common_flag'],",
+        ")",
+        "feature_flag_setter(",
+        "    name = 'right',",
+        "    deps = [':common'],",
+        "    flag_values = {",
+        "        ':different_flag': 'right',",
+        "        ':common_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':different_flag', ':common_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'common',",
+        "    flags = [':common_flag'],",
+        "    transitive_configs = [':different_flag', ':common_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'different_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")",
+        "config_feature_flag(",
+        "    name = 'common_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact leftFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:left")).toList());
+    Artifact rightFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:right")).toList());
+
+    assertThat(leftFlags).isNotEqualTo(rightFlags);
+    assertThat(leftFlags.getArtifactOwner()).isNotEqualTo(rightFlags.getArtifactOwner());
+  }
+
+  @Test
+  public void emptyTransitiveConfigs_EquivalentRegardlessOfFeatureFlags() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'left',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':used_flag': 'left',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "feature_flag_setter(",
+        "    name = 'right',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':used_flag': 'right',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    transitive_configs = [],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact leftFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:left")).toList());
+    Artifact rightFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:right")).toList());
+    Artifact directFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:reader")).toList());
+
+    assertThat(leftFlags).isEqualTo(rightFlags);
+    assertThat(leftFlags).isEqualTo(directFlags);
+  }
+
+  @Test
+  public void absentTransitiveConfigs_EquivalentRegardlessOfFeatureFlags() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'left',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':used_flag': 'left',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "feature_flag_setter(",
+        "    name = 'right',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':used_flag': 'right',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        // no transitive_configs = equivalent to []
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact leftFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:left")).toList());
+    Artifact rightFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:right")).toList());
+    Artifact directFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:reader")).toList());
+
+    assertThat(leftFlags).isEqualTo(rightFlags);
+    assertThat(leftFlags).isEqualTo(directFlags);
+  }
+
+  @Test
+  public void nonexistentLabelInTransitiveConfigs_DoesNotError() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':trimmed_flag': 'left',",
+        "    },",
+        "    transitive_configs = [':false_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    transitive_configs = [':false_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'trimmed_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")");
+
+    getConfiguredTarget("//test:target");
+    assertNoEvents();
+  }
+
+  @Test
+  public void flagSetBySetterButNotInTransitiveConfigs_CanBeUsedByDeps() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':not_actually_trimmed_flag': 'left',",
+        "    },",
+        "    transitive_configs = [],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':not_actually_trimmed_flag'],",
+        "    transitive_configs = [':not_actually_trimmed_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'not_actually_trimmed_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")");
+
+    getConfiguredTarget("//test:target");
+    assertNoEvents();
+  }
+
+  @Test
+  public void featureFlagInUnusedSelectBranchButNotInTransitiveConfigs_DoesNotError()
+      throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':trimmed_flag': 'left',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = select({':used_flag@other': [':trimmed_flag'], '//conditions:default': []}),",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "config_setting(",
+        "    name = 'used_flag@other',",
+        "    flag_values = {':used_flag': 'other'},",
+        ")",
+        "config_feature_flag(",
+        "    name = 'trimmed_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    getConfiguredTarget("//test:target");
+    assertNoEvents();
+  }
+
+  @Test
+  public void featureFlagTarget_IsTrimmedToOnlyItself() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    exports_flag = ':read_flag',",
+        "    flag_values = {",
+        "        ':trimmed_flag': 'left',",
+        "        ':read_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':trimmed_flag', ':read_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'trimmed_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")",
+        "config_feature_flag(",
+        "    name = 'read_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    ConfiguredTarget target = getConfiguredTarget("//test:target");
+    RuleContext ruleContext = getRuleContext(target);
+    BuildConfiguration childConfiguration =
+        Iterables.getOnlyElement(ruleContext.getPrerequisiteConfiguredTargetAndTargets("exports_flag", Mode.TARGET)).getConfiguration();
+
+    Label childLabel = Label.parseAbsoluteUnchecked("//test:read_flag");
+    assertThat(getFlagMapFromConfiguration(childConfiguration).keySet())
+        .containsExactly(childLabel);
+  }
+
+  @Test
+  public void featureFlagAccessedByPathWithMissingLabel_ProducesError() throws Exception {
+    reporter.removeHandler(failFastHandler); // expecting an error
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':broken'],",
+        "    flag_values = {",
+        "        ':used_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "filegroup(",
+        "    name = 'broken',",
+        "    srcs = [':reader'],",
+        "    transitive_configs = [],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':used_flag'],",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    assertThat(getConfiguredTarget("//test:target")).isNull();
+    assertContainsEvent(
+        "Feature flag //test:used_flag was accessed in a configuration it is not present in. All "
+            + "targets which depend on //test:used_flag directly or indirectly must name it in "
+            + "their transitive_configs attribute.");
+  }
+
+  @Test
+  public void featureFlagAccessedByPathWithMissingTransitiveConfigs_ProducesError()
+      throws Exception {
+    reporter.removeHandler(failFastHandler); // expecting an error
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':broken'],",
+        "    flag_values = {",
+        "        ':used_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "filegroup(",
+        "    name = 'broken',",
+        "    srcs = [':reader'],",
+        // no transitive_configs = equivalent to []
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':used_flag'],",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    assertThat(getConfiguredTarget("//test:target")).isNull();
+    assertContainsEvent(
+        "Feature flag //test:used_flag was accessed in a configuration it is not present in. All "
+            + "targets which depend on //test:used_flag directly or indirectly must name it in "
+            + "their transitive_configs attribute.");
+  }
+
+  @Test
+  public void featureFlagInHostConfiguration_HasDefaultValue() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':host_transition.bzl', 'host_transition')",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':host'],",
+        "    flag_values = {",
+        "        ':used_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "host_transition(",
+        "    name = 'host',",
+        "    srcs = [':reader'],",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':used_flag'],",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact targetFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:target")).toList());
+
+    Label usedFlag = Label.parseAbsolute("//test:used_flag");
+    assertThat(getFlagValuesFromOutputFile(targetFlags)).containsEntry(usedFlag, "default");
+  }
+
+  @Test
+  public void featureFlagInHostConfiguration_HasNoTransitiveConfigEnforcement() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':host_transition.bzl', 'host_transition')",
+        "load(':read_flags.bzl', 'read_flags')",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':host'],",
+        "    flag_values = {",
+        "        ':used_flag': 'configured',",
+        "    },",
+        // no transitive_configs
+        ")",
+        "host_transition(",
+        "    name = 'host',",
+        "    srcs = [':reader'],",
+        // no transitive_configs
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':used_flag'],",
+        // no transitive_configs
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    getConfiguredTarget("//test:target");
+    assertNoEvents();
+  }
+
+  @Test
+  public void featureFlagAccessedDirectly_ReturnsDefaultValue() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    assertThat(
+            ConfigFeatureFlagProvider.fromTarget(getConfiguredTarget("//test:used_flag"))
+                .getValue())
+        .isEqualTo("default");
+  }
+
+  @Test
+  public void featureFlagAccessedViaTopLevelLibraryTarget_ReturnsDefaultValue() throws Exception {
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':used_flag'],",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+    Artifact targetFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:reader")).toList());
+
+    Label usedFlag = Label.parseAbsolute("//test:used_flag");
+    assertThat(getFlagValuesFromOutputFile(targetFlags)).containsEntry(usedFlag, "default");
+  }
+
+  @Test
+  public void featureFlagSettingRules_OverrideFlagsFromReverseTransitiveClosure()
+      throws Exception {
+    // In other words: if you have a dependency which sets feature flags itself, you don't need to
+    // name any of the feature flags used by that target or its transitive closure, as it sets
+    // feature flags itself.
+    // This is because the feature flag setting transition (which calls replaceFlagValues) runs
+    // before the trimming transition and completely replaces the feature flag set. Thus, when
+    // the trimming transition (which calls trimFlagValues) runs, its requests are always satisfied.
+
+    scratch.file(
+        "test/BUILD",
+        "load(':read_flags.bzl', 'read_flags')",
+        "filegroup(",
+        "    name = 'toplevel',",
+        "    srcs = [':target'],",
+        // no transitive_configs
+        ")",
+        "feature_flag_setter(",
+        "    name = 'target',",
+        "    deps = [':reader'],",
+        "    flag_values = {",
+        "        ':trimmed_flag': 'left',",
+        "        ':used_flag': 'configured',",
+        "    },",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "read_flags(",
+        "    name = 'reader',",
+        "    flags = [':used_flag'],",
+        "    transitive_configs = [':used_flag'],",
+        ")",
+        "config_feature_flag(",
+        "    name = 'trimmed_flag',",
+        "    allowed_values = ['default', 'left', 'right'],",
+        "    default_value = 'default',",
+        ")",
+        "config_feature_flag(",
+        "    name = 'used_flag',",
+        "    allowed_values = ['default', 'configured', 'other'],",
+        "    default_value = 'default',",
+        ")");
+
+    Artifact targetFlags =
+        Iterables.getOnlyElement(getFilesToBuild(getConfiguredTarget("//test:toplevel")).toList());
+
+    Label usedFlag = Label.parseAbsolute("//test:used_flag");
+    assertThat(getFlagValuesFromOutputFile(targetFlags)).containsEntry(usedFlag, "configured");
+  }
+}
diff --git a/src/test/java/com/google/devtools/build/lib/rules/objc/AppleBinaryTest.java b/src/test/java/com/google/devtools/build/lib/rules/objc/AppleBinaryTest.java
index 51c145a84f..cc8fb258eb 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/objc/AppleBinaryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/objc/AppleBinaryTest.java
@@ -1494,6 +1494,7 @@ public class AppleBinaryTest extends ObjcRuleTestCase {
 
   @Test
   public void testFeatureFlags_offByDefault() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratchFeatureFlagTestLib();
     scratch.file(
         "test/BUILD",
@@ -1501,6 +1502,7 @@ public class AppleBinaryTest extends ObjcRuleTestCase {
         "    name = 'bin',",
         "    deps = ['//lib:objcLib'],",
         "    platform_type = 'ios',",
+        "    transitive_configs = ['//lib:flag1', '//lib:flag2'],",
         ")");
 
     CommandAction linkAction = linkAction("//test:bin");
@@ -1522,6 +1524,7 @@ public class AppleBinaryTest extends ObjcRuleTestCase {
 
   @Test
   public void testFeatureFlags_oneFlagOn() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratchFeatureFlagTestLib();
     scratch.file(
         "test/BUILD",
@@ -1531,7 +1534,8 @@ public class AppleBinaryTest extends ObjcRuleTestCase {
         "    platform_type = 'ios',",
         "    feature_flags = {",
         "      '//lib:flag2': 'on',",
-        "    }",
+        "    },",
+        "    transitive_configs = ['//lib:flag1', '//lib:flag2'],",
         ")");
 
     CommandAction linkAction = linkAction("//test:bin");
@@ -1553,6 +1557,7 @@ public class AppleBinaryTest extends ObjcRuleTestCase {
 
   @Test
   public void testFeatureFlags_allFlagsOn() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratchFeatureFlagTestLib();
     scratch.file(
         "test/BUILD",
@@ -1563,7 +1568,8 @@ public class AppleBinaryTest extends ObjcRuleTestCase {
         "    feature_flags = {",
         "      '//lib:flag1': 'on',",
         "      '//lib:flag2': 'on',",
-        "    }",
+        "    },",
+        "    transitive_configs = ['//lib:flag1', '//lib:flag2'],",
         ")");
 
     CommandAction linkAction = linkAction("//test:bin");
diff --git a/src/test/java/com/google/devtools/build/lib/rules/objc/AppleStaticLibraryTest.java b/src/test/java/com/google/devtools/build/lib/rules/objc/AppleStaticLibraryTest.java
index f8d056ad9e..2649ebca97 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/objc/AppleStaticLibraryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/objc/AppleStaticLibraryTest.java
@@ -567,6 +567,7 @@ public class AppleStaticLibraryTest extends ObjcRuleTestCase {
 
   @Test
   public void testFeatureFlags_offByDefault() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratchFeatureFlagTestLib();
     scratch.file(
         "test/BUILD",
@@ -574,6 +575,7 @@ public class AppleStaticLibraryTest extends ObjcRuleTestCase {
         "    name = 'static_lib',",
         "    deps = ['//lib:objcLib'],",
         "    platform_type = 'ios',",
+        "    transitive_configs = ['//lib:flag1', '//lib:flag2'],",
         ")");
 
     CommandAction linkAction = linkLibAction("//test:static_lib");
@@ -595,6 +597,7 @@ public class AppleStaticLibraryTest extends ObjcRuleTestCase {
 
   @Test
   public void testFeatureFlags_oneFlagOn() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratchFeatureFlagTestLib();
     scratch.file(
         "test/BUILD",
@@ -604,7 +607,8 @@ public class AppleStaticLibraryTest extends ObjcRuleTestCase {
         "    platform_type = 'ios',",
         "    feature_flags = {",
         "      '//lib:flag2': 'on',",
-        "    }",
+        "    },",
+        "    transitive_configs = ['//lib:flag1', '//lib:flag2'],",
         ")");
 
     CommandAction linkAction = linkLibAction("//test:static_lib");
@@ -626,6 +630,7 @@ public class AppleStaticLibraryTest extends ObjcRuleTestCase {
 
   @Test
   public void testFeatureFlags_allFlagsOn() throws Exception {
+    useConfiguration("--enforce_transitive_configs_for_config_feature_flag");
     scratchFeatureFlagTestLib();
     scratch.file(
         "test/BUILD",
@@ -636,7 +641,8 @@ public class AppleStaticLibraryTest extends ObjcRuleTestCase {
         "    feature_flags = {",
         "      '//lib:flag1': 'on',",
         "      '//lib:flag2': 'on',",
-        "    }",
+        "    },",
+        "    transitive_configs = ['//lib:flag1', '//lib:flag2'],",
         ")");
 
     CommandAction linkAction = linkLibAction("//test:static_lib");
diff --git a/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcRuleTestCase.java b/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcRuleTestCase.java
index 598eda0fc0..4b72583b21 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcRuleTestCase.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcRuleTestCase.java
@@ -2267,6 +2267,7 @@ public abstract class ObjcRuleTestCase extends BuildViewTestCase {
         "config_setting(",
         "  name = 'flag1@on',",
         "  flag_values = {':flag1': 'on'},",
+        "  transitive_configs = [':flag1'],",
         ")",
         "config_feature_flag(",
         "  name = 'flag2',",
@@ -2276,6 +2277,7 @@ public abstract class ObjcRuleTestCase extends BuildViewTestCase {
         "config_setting(",
         "  name = 'flag2@on',",
         "  flag_values = {':flag2': 'on'},",
+        "  transitive_configs = [':flag2'],",
         ")",
         "objc_library(",
         "  name = 'objcLib',",
@@ -2293,6 +2295,7 @@ public abstract class ObjcRuleTestCase extends BuildViewTestCase {
         "    ':flag2@on': ['-FLAG_2_ON'],",
         "    '//conditions:default': ['-FLAG_2_OFF'],",
         "  }),",
+        "  transitive_configs = [':flag1', ':flag2'],",
         ")");
   }
 }
diff --git a/src/test/java/com/google/devtools/build/lib/skylark/SkylarkRuleContextTest.java b/src/test/java/com/google/devtools/build/lib/skylark/SkylarkRuleContextTest.java
index 8c4b7df066..e449ed1ceb 100644
--- a/src/test/java/com/google/devtools/build/lib/skylark/SkylarkRuleContextTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skylark/SkylarkRuleContextTest.java
@@ -613,6 +613,7 @@ public class SkylarkRuleContextTest extends SkylarkTestCase {
     assertThat(result).containsExactly(
         "name",
         "visibility",
+        "transitive_configs",
         "tags",
         "generator_name",
         "generator_function",
-- 
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