Relax requirements of skylark-exposed configuration fragments

Since configuration fragments will extend from build API classes, @SkylarkConfigurationField no longer needs to annotate a method defined on a @SkylarkModule class. Ideally, we would ensure that a configuration fragment with a @SkylarkConfigurationField method implements an interface with @SkylarkModule, but this seems impossible to perform at the level of an annotation processor.

RELNOTES: None.
PiperOrigin-RevId: 195651344

3 files changed, 65 insertions, 6 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/SkylarkConfigurationFieldProcessorTest.java b/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/SkylarkConfigurationFieldProcessorTest.java
index 4f6bc4dfb6..d17b226ccd 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/SkylarkConfigurationFieldProcessorTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/SkylarkConfigurationFieldProcessorTest.java
@@ -50,6 +50,18 @@ public final class SkylarkConfigurationFieldProcessorTest {
   }
 
   @Test
+  public void testGoldenConfigurationFieldThroughApi() throws Exception {
+    // TODO(b/71644521): Compile-testing is not fully functional on Windows; test sources are
+    // unable to resolve cross-package dependencies.
+    assumeTrue(OS.getCurrent() != OS.WINDOWS);
+
+    assertAbout(javaSource())
+        .that(getFile("GoldenConfigurationFieldThroughApi.java"))
+        .processedWith(new SkylarkConfigurationFieldProcessor())
+        .compilesWithoutError();
+  }
+
+  @Test
   public void testHasMethodParameters() throws Exception {
     // TODO(b/71644521): Compile-testing is not fully functional on Windows; test sources are
     // unable to resolve cross-package dependencies.
@@ -99,8 +111,8 @@ public final class SkylarkConfigurationFieldProcessorTest {
         .that(getFile("NonConfigurationFragment.java"))
         .processedWith(new SkylarkConfigurationFieldProcessor())
         .failsToCompile()
-        .withErrorContaining("@SkylarkConfigurationField annotated methods must be methods of "
-            + "configuration fragments with the @SkylarkModule annotation.");
+        .withErrorContaining("@SkylarkConfigurationField annotated methods must be methods "
+            + "of configuration fragments.");
   }
 
   @Test
@@ -112,9 +124,7 @@ public final class SkylarkConfigurationFieldProcessorTest {
     assertAbout(javaSource())
         .that(getFile("NonExposedConfigurationFragment.java"))
         .processedWith(new SkylarkConfigurationFieldProcessor())
-        .failsToCompile()
-        .withErrorContaining("@SkylarkConfigurationField annotated methods must be methods of "
-            + "configuration fragments with the @SkylarkModule annotation.");
+        .compilesWithoutError();
   }
 
   @Test
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/optiontestsources/GoldenConfigurationFieldThroughApi.java b/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/optiontestsources/GoldenConfigurationFieldThroughApi.java
new file mode 100644
index 0000000000..29bca7fe24
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/optiontestsources/GoldenConfigurationFieldThroughApi.java
@@ -0,0 +1,49 @@
+// Copyright 2017 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.analysis.skylark.annotations.processor.optiontestsources;
+
+import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
+import com.google.devtools.build.lib.analysis.skylark.annotations.SkylarkConfigurationField;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
+
+/**
+ * A test case of SkylarkConfigurationFieldProcessorTest.
+ */
+public class GoldenConfigurationFieldThroughApi
+    extends BuildConfiguration.Fragment implements ApiInterface {
+
+  /**
+   * Returns the label of the xcode_config rule to use for resolving the host system xcode version.
+   */
+  @SkylarkConfigurationField(
+      name = "some_field",
+      doc = "Documentation ",
+      defaultLabel = "defaultLabel",
+      defaultInToolRepository = true
+  )
+  public Label getXcodeConfigLabel() {
+    return null;
+  }
+}
+
+@SkylarkModule(
+    name = "module_name",
+    doc = "A fake configuration fragment for a test.",
+    category = SkylarkModuleCategory.CONFIGURATION_FRAGMENT
+)
+interface ApiInterface {
+}
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/optiontestsources/NonConfigurationFragment.java b/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/optiontestsources/NonConfigurationFragment.java
index 221493775f..f21175f2fb 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/optiontestsources/NonConfigurationFragment.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/skylark/annotations/processor/optiontestsources/NonConfigurationFragment.java
@@ -25,7 +25,7 @@ import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
 @SkylarkModule(
     name = "module_name",
     doc = "A fake configuration fragment for a test.",
-    category = SkylarkModuleCategory.CONFIGURATION_FRAGMENT
+    category = SkylarkModuleCategory.BUILTIN  // Not a configuration fragment!
 )
 public class NonConfigurationFragment {