Fake StarlarkExposedRuleTransitionFactory for the Starlark common api

PiperOrigin-RevId: 396656234

src/main/java/com/google/devtools/build/skydoc/fakebuildapi/BUILD

@@ -15,8 +15,11 @@ java_library(
     srcs = glob(["**/*.java"]),
     deps = [
         "//src/main/java/com/google/devtools/build/lib/actions:artifacts",
+        "//src/main/java/com/google/devtools/build/lib/analysis:config/transitions/patch_transition",
         "//src/main/java/com/google/devtools/build/lib/analysis:config/transitions/starlark_exposed_rule_transition_factory",
+        "//src/main/java/com/google/devtools/build/lib/analysis:rule_definition_environment",
         "//src/main/java/com/google/devtools/build/lib/cmdline",
+        "//src/main/java/com/google/devtools/build/lib/packages",
         "//src/main/java/com/google/devtools/build/lib/starlarkbuildapi",
         "//src/main/java/com/google/devtools/build/lib/starlarkbuildapi/config",
         "//src/main/java/com/google/devtools/build/lib/starlarkbuildapi/core",

src/main/java/com/google/devtools/build/skydoc/fakebuildapi/config/FakeConfigFeatureFlagTransitionFactory.java

@@ -0,0 +1,34 @@
+// Copyright 2021 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.skydoc.fakebuildapi.config;
+
+import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
+import com.google.devtools.build.lib.analysis.config.transitions.PatchTransition;
+import com.google.devtools.build.lib.analysis.config.transitions.StarlarkExposedRuleTransitionFactory;
+import com.google.devtools.build.lib.packages.RuleClass;
+import com.google.devtools.build.lib.packages.RuleTransitionData;
+
+/** Fake callable implementation of {@link StarlarkExposedRuleTransitionFactory}. */
+public class FakeConfigFeatureFlagTransitionFactory
+    implements StarlarkExposedRuleTransitionFactory {
+
+  @Override
+  public void addToStarlarkRule(RuleDefinitionEnvironment ctx, RuleClass.Builder builder) {}
+
+  @Override
+  public PatchTransition create(RuleTransitionData ruleData) {
+    return null;
+  }
+}

src/main/java/com/google/devtools/build/skydoc/fakebuildapi/config/FakeConfigStarlarkCommon.java

@@ -32,6 +32,6 @@ public ProviderApi getConfigFeatureFlagProviderConstructor() {
   @Override
   public StarlarkExposedRuleTransitionFactory createConfigFeatureFlagTransitionFactory(
       String attribute) {
-    return null;
+    return new FakeConfigFeatureFlagTransitionFactory();
   }
 }