Test suite to verify contracts of @SkylarkCallable and @SkylarkModule which are difficult or impossible to verify by annotation processor.

RELNOTES: None.
PiperOrigin-RevId: 204540521

2 files changed, 86 insertions, 0 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/skylark/BUILD b/src/test/java/com/google/devtools/build/lib/skylark/BUILD
index ca3ef36b21..bfb8499c41 100644
--- a/src/test/java/com/google/devtools/build/lib/skylark/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/skylark/BUILD
@@ -51,6 +51,7 @@ java_test(
         "//src/main/java/com/google/devtools/build/lib:bazel-main",
         "//src/main/java/com/google/devtools/build/lib:bazel-rules",
         "//src/main/java/com/google/devtools/build/lib:build-base",
+        "//src/main/java/com/google/devtools/build/lib:classpath-util",
         "//src/main/java/com/google/devtools/build/lib:events",
         "//src/main/java/com/google/devtools/build/lib:java-compilation",
         "//src/main/java/com/google/devtools/build/lib:java-rules",
diff --git a/src/test/java/com/google/devtools/build/lib/skylark/SkylarkAnnotationContractTest.java b/src/test/java/com/google/devtools/build/lib/skylark/SkylarkAnnotationContractTest.java
new file mode 100644
index 0000000000..7be287b97f
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/skylark/SkylarkAnnotationContractTest.java
@@ -0,0 +1,85 @@
+// 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.skylark;
+
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkInterfaceUtils;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.util.Classpath;
+import java.lang.reflect.Method;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests that bazel usages of {@link SkylarkCallable} and {@link SkylarkModule} abide by the
+ * contracts specified in their documentation.
+ *
+ * <p>Tests in this class use the java reflection API.</p>
+ *
+ * <p>This verification *would* be done via annotation processor, but annotation processors in
+ * java don't have access to the full set of information that the java reflection API has.</p>
+ */
+@RunWith(JUnit4.class)
+public class SkylarkAnnotationContractTest {
+
+  // Common prefix of packages in bazel that may have classes that implement or extend a
+  // Skylark type.
+  private static final String MODULES_PACKAGE_PREFIX = "com/google/devtools/build";
+
+  /**
+   * Verifies that every class in bazel that implements or extends a Skylark type has a clearly
+   * resolvable type.
+   *
+   * <p>If this test fails, it indicates the following error scenario:
+   *
+   * <p>Suppose class A is a subclass of both B and C, where B and C are annotated with
+   * @SkylarkModule annotations (and are thus considered "skylark types"). If B is not a
+   * subclass of C (nor visa versa), then it's impossible to resolve whether A is of type
+   * B or if A is of type C. It's both! The way to resolve this is usually to have A be its own
+   * type (annotated with @SkylarkModule), and thus have the explicit type of A be semantically
+   * "B and C".
+   */
+  @Test
+  public void testResolvableSkylarkModules() throws Exception {
+    for (Class<?> candidateClass : Classpath.findClasses(MODULES_PACKAGE_PREFIX)) {
+      SkylarkInterfaceUtils.getSkylarkModule(candidateClass);
+    }
+  }
+
+  /**
+   * Verifies that no class or interface has a method annotated with {@link SkylarkCallable} unless
+   * that class or interface is annotated with either {@link SkylarkGlobalLibrary} or with
+   * {@link SkylarkModule}.
+   */
+  @Test
+  public void testSkylarkCallableScope() throws Exception {
+    for (Class<?> candidateClass : Classpath.findClasses(MODULES_PACKAGE_PREFIX)) {
+      if (SkylarkInterfaceUtils.getSkylarkModule(candidateClass) == null
+          && !SkylarkInterfaceUtils.hasSkylarkGlobalLibrary(candidateClass)) {
+        for (Method method : candidateClass.getMethods()) {
+          SkylarkCallable callable = SkylarkInterfaceUtils.getSkylarkCallable(method);
+          if (callable != null && method.getDeclaringClass() == candidateClass) {
+            throw new AssertionError(String.format(
+                "Class %s has a SkylarkCallable method %s but is neither a @SkylarkModule nor a "
+                    + "@SkylarkGlobalLibrary",
+                candidateClass,
+                method.getName()));
+          }
+        }
+      }
+    }
+  }
+}