Refactor getAnnotationFromParentClass() to a new SkylarkInterfaceUtils module

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MOS_MIGRATED_REVID=135144084

1 files changed, 73 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkInterfaceUtils.java b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkInterfaceUtils.java
new file mode 100644
index 0000000000..95d4f4fcf5
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkInterfaceUtils.java
@@ -0,0 +1,73 @@
+// Copyright 2016 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.skylarkinterface;
+
+import java.lang.reflect.Method;
+import javax.annotation.Nullable;
+
+/**
+ * Helpers for accessing Skylark interface annotations.
+ */
+public class SkylarkInterfaceUtils {
+
+  /**
+   * Returns the {@link SkylarkCallable} annotation for the given method, if it exists, and
+   * null otherwise. The method must be declared in {@code classObj} or one of its base classes
+   * or interfaces. The first annotation of an overridden version of the method that is found
+   * will be returned, starting with {@code classObj} and following its base classes and
+   * interfaces recursively.
+   */
+  @Nullable
+  public static SkylarkCallable getSkylarkCallable(Class<?> classObj, Method method) {
+    boolean keepLooking = false;
+    try {
+      Method superMethod = classObj.getMethod(method.getName(), method.getParameterTypes());
+      if (classObj.isAnnotationPresent(SkylarkModule.class)
+          && superMethod.isAnnotationPresent(SkylarkCallable.class)) {
+        return superMethod.getAnnotation(SkylarkCallable.class);
+      } else {
+        keepLooking = true;
+      }
+    } catch (NoSuchMethodException e) {
+      // The class might not have the specified method, so an exceptions is OK.
+      keepLooking = true;
+    }
+    if (keepLooking) {
+      if (classObj.getSuperclass() != null) {
+        SkylarkCallable annotation =
+            getSkylarkCallable(classObj.getSuperclass(), method);
+        if (annotation != null) {
+          return annotation;
+        }
+      }
+      for (Class<?> interfaceObj : classObj.getInterfaces()) {
+        SkylarkCallable annotation = getSkylarkCallable(interfaceObj, method);
+        if (annotation != null) {
+          return annotation;
+        }
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Convenience version of {@code getAnnotationsFromParentClass(Class, Method)} that uses
+   * the declaring class of the method.
+   */
+  @Nullable
+  public static SkylarkCallable getSkylarkCallable(Method method) {
+    return getSkylarkCallable(method.getDeclaringClass(), method);
+  }
+}