Automated rollback of commit 2b983bdf508e010a3d4ee9dbaf446b7666749799.

*** Reason for rollback ***

Breaks rules_go CI

*** Original change description ***

Rollforward of c++ toolchain-relevant BUILD file and Bazel mocking changes.  That is, a c++ toolchain is added, but a Bazel dependency on that toolchain is not.

PiperOrigin-RevId: 167198874

5 files changed, 39 insertions, 64 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/BaseRuleClasses.java b/src/main/java/com/google/devtools/build/lib/analysis/BaseRuleClasses.java
index f52d66f209..817f4d163e 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/BaseRuleClasses.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/BaseRuleClasses.java
@@ -182,60 +182,41 @@ public class BaseRuleClasses {
    * Share common attributes across both base and Skylark base rules.
    */
   public static RuleClass.Builder commonCoreAndSkylarkAttributes(RuleClass.Builder builder) {
-    return PlatformSemantics.platformAttributes(builder)
+    return builder
         // The visibility attribute is special: it is a nodep label, and loading the
         // necessary package groups is handled by {@link LabelVisitor#visitTargetVisibility}.
         // Package groups always have the null configuration so that they are not duplicated
         // needlessly.
-        .add(
-            attr("visibility", NODEP_LABEL_LIST)
-                .orderIndependent()
-                .cfg(HOST)
-                .nonconfigurable(
-                    "special attribute integrated more deeply into Bazel's core logic"))
-        .add(
-            attr("deprecation", STRING)
-                .value(deprecationDefault)
-                .nonconfigurable("Used in core loading phase logic with no access to configs"))
-        .add(
-            attr("tags", STRING_LIST)
-                .orderIndependent()
-                .taggable()
-                .nonconfigurable("low-level attribute, used in TargetUtils without configurations"))
-        .add(
-            attr("generator_name", STRING)
-                .undocumented("internal")
-                .nonconfigurable("static structure of a rule"))
-        .add(
-            attr("generator_function", STRING)
-                .undocumented("internal")
-                .nonconfigurable("static structure of a rule"))
-        .add(
-            attr("generator_location", STRING)
-                .undocumented("internal")
-                .nonconfigurable("static structure of a rule"))
-        .add(
-            attr("testonly", BOOLEAN)
-                .value(testonlyDefault)
-                .nonconfigurable("policy decision: rules testability should be consistent"))
+        .add(attr("visibility", NODEP_LABEL_LIST).orderIndependent().cfg(HOST)
+            .nonconfigurable("special attribute integrated more deeply into Bazel's core logic"))
+        .add(attr("deprecation", STRING).value(deprecationDefault)
+            .nonconfigurable("Used in core loading phase logic with no access to configs"))
+        .add(attr("tags", STRING_LIST).orderIndependent().taggable()
+            .nonconfigurable("low-level attribute, used in TargetUtils without configurations"))
+        .add(attr("generator_name", STRING).undocumented("internal")
+            .nonconfigurable("static structure of a rule"))
+        .add(attr("generator_function", STRING).undocumented("internal")
+            .nonconfigurable("static structure of a rule"))
+        .add(attr("generator_location", STRING).undocumented("internal")
+            .nonconfigurable("static structure of a rule"))
+        .add(attr("testonly", BOOLEAN).value(testonlyDefault)
+            .nonconfigurable("policy decision: rules testability should be consistent"))
         .add(attr("features", STRING_LIST).orderIndependent())
         .add(attr(":action_listener", LABEL_LIST).cfg(HOST).value(ACTION_LISTENER))
-        .add(
-            attr(RuleClass.COMPATIBLE_ENVIRONMENT_ATTR, LABEL_LIST)
-                .allowedRuleClasses(EnvironmentRule.RULE_NAME)
-                .cfg(Attribute.ConfigurationTransition.HOST)
-                .allowedFileTypes(FileTypeSet.NO_FILE)
-                .dontCheckConstraints()
-                .nonconfigurable(
-                    "special logic for constraints and select: see ConstraintSemantics"))
-        .add(
-            attr(RuleClass.RESTRICTED_ENVIRONMENT_ATTR, LABEL_LIST)
-                .allowedRuleClasses(EnvironmentRule.RULE_NAME)
-                .cfg(Attribute.ConfigurationTransition.HOST)
-                .allowedFileTypes(FileTypeSet.NO_FILE)
-                .dontCheckConstraints()
-                .nonconfigurable(
-                    "special logic for constraints and select: see ConstraintSemantics"));
+        .add(attr(RuleClass.COMPATIBLE_ENVIRONMENT_ATTR, LABEL_LIST)
+            .allowedRuleClasses(EnvironmentRule.RULE_NAME)
+            .cfg(Attribute.ConfigurationTransition.HOST)
+            .allowedFileTypes(FileTypeSet.NO_FILE)
+            .dontCheckConstraints()
+            .nonconfigurable("special logic for constraints and select: see ConstraintSemantics")
+        )
+        .add(attr(RuleClass.RESTRICTED_ENVIRONMENT_ATTR, LABEL_LIST)
+            .allowedRuleClasses(EnvironmentRule.RULE_NAME)
+            .cfg(Attribute.ConfigurationTransition.HOST)
+            .allowedFileTypes(FileTypeSet.NO_FILE)
+            .dontCheckConstraints()
+            .nonconfigurable("special logic for constraints and select: see ConstraintSemantics")
+        );
   }
 
   public static RuleClass.Builder nameAttribute(RuleClass.Builder builder) {
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/PlatformOptions.java b/src/main/java/com/google/devtools/build/lib/analysis/PlatformOptions.java
index 3a84352105..3376e9609d 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/PlatformOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/PlatformOptions.java
@@ -36,7 +36,7 @@ public class PlatformOptions extends FragmentOptions {
   @Option(
     name = "experimental_host_platform",
     converter = BuildConfiguration.LabelConverter.class,
-    defaultValue = "@bazel_tools//tools/platforms:host_platform",
+    defaultValue = "@bazel_tools//platforms:host_platform",
     documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
     effectTags = {OptionEffectTag.UNKNOWN},
     metadataTags = {OptionMetadataTag.HIDDEN},
@@ -49,7 +49,7 @@ public class PlatformOptions extends FragmentOptions {
   @Option(
     name = "experimental_platforms",
     converter = BuildConfiguration.LabelListConverter.class,
-    defaultValue = "@bazel_tools//tools/platforms:target_platform",
+    defaultValue = "@bazel_tools//platforms:target_platform",
     documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
     effectTags = {OptionEffectTag.UNKNOWN},
     metadataTags = {OptionMetadataTag.HIDDEN},
@@ -98,8 +98,6 @@ public class PlatformOptions extends FragmentOptions {
   public PlatformOptions getHost(boolean fallback) {
     PlatformOptions host = (PlatformOptions) getDefault();
     host.platforms = ImmutableList.of(this.hostPlatform);
-    host.hostPlatform = this.hostPlatform;
-    host.extraToolchains = this.extraToolchains;
     return host;
   }
 
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/PlatformSemantics.java b/src/main/java/com/google/devtools/build/lib/analysis/PlatformSemantics.java
index 45c967e551..d93c5a6dea 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/PlatformSemantics.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/PlatformSemantics.java
@@ -26,7 +26,6 @@ import com.google.devtools.build.lib.packages.AttributeMap;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import java.util.List;
-import javax.annotation.Nullable;
 
 /** Helper class to manage rules' use of platforms. */
 public class PlatformSemantics {
@@ -41,22 +40,19 @@ public class PlatformSemantics {
         @Override
         public List<Label> resolve(
             Rule rule, AttributeMap attributes, BuildConfiguration configuration) {
-          // rule may be null for tests
-          if (rule == null || rule.getRuleClassObject().getRequiredToolchains().isEmpty()) {
-            return ImmutableList.of();
+          if (rule.getRuleClassObject().getRequiredToolchains().isEmpty()) {
+            return null;
           }
           return configuration.getFragment(PlatformConfiguration.class).getTargetPlatforms();
         }
       };
 
   /** Implementation for the :execution_platform attribute. */
-  @Nullable
   public static final Attribute.LateBoundLabel<BuildConfiguration> EXECUTION_PLATFORM =
       new Attribute.LateBoundLabel<BuildConfiguration>(PlatformConfiguration.class) {
         @Override
         public Label resolve(Rule rule, AttributeMap attributes, BuildConfiguration configuration) {
-          // rule may be null for tests
-          if (rule == null || rule.getRuleClassObject().getRequiredToolchains().isEmpty()) {
+          if (rule.getRuleClassObject().getRequiredToolchains().isEmpty()) {
             return null;
           }
           return configuration.getFragment(PlatformConfiguration.class).getExecutionPlatform();
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/ToolchainContext.java b/src/main/java/com/google/devtools/build/lib/analysis/ToolchainContext.java
index 16a29fd5df..9cbdd475ac 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/ToolchainContext.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/ToolchainContext.java
@@ -142,8 +142,6 @@ public class ToolchainContext {
         prerequisiteMap
             .keys()
             .stream()
-            // Keys in prerequisiteMap can be null, see {@link DependencyResolver#dependentNodeMap}.
-            .filter(attribute -> attribute != null)
             .filter(attribute -> attribute.getName().equals(PlatformSemantics.TOOLCHAINS_ATTR))
             .findFirst();
     Preconditions.checkState(
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleClassFunctions.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleClassFunctions.java
index 6c8487364d..3e850d966d 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleClassFunctions.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleClassFunctions.java
@@ -39,6 +39,7 @@ import com.google.devtools.build.lib.analysis.ActionsProvider;
 import com.google.devtools.build.lib.analysis.BaseRuleClasses;
 import com.google.devtools.build.lib.analysis.DefaultInfo;
 import com.google.devtools.build.lib.analysis.OutputGroupProvider;
+import com.google.devtools.build.lib.analysis.PlatformSemantics;
 import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
 import com.google.devtools.build.lib.analysis.skylark.SkylarkAttr.Descriptor;
 import com.google.devtools.build.lib.analysis.test.TestConfiguration;
@@ -128,9 +129,10 @@ public class SkylarkRuleClassFunctions {
   /** Parent rule class for non-executable non-test Skylark rules. */
   public static final RuleClass baseRule =
       BaseRuleClasses.commonCoreAndSkylarkAttributes(
-              BaseRuleClasses.nameAttribute(
-                      new RuleClass.Builder("$base_rule", RuleClassType.ABSTRACT, true))
-                  .add(attr("expect_failure", STRING)))
+              PlatformSemantics.platformAttributes(
+                  BaseRuleClasses.nameAttribute(
+                          new RuleClass.Builder("$base_rule", RuleClassType.ABSTRACT, true))
+                      .add(attr("expect_failure", STRING))))
           .build();
 
   /** Parent rule class for executable non-test Skylark rules. */