Start refactoring elements of the Skylark Build API into their own package.

RELNOTES: None.
PiperOrigin-RevId: 193962460

9 files changed, 145 insertions, 38 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/BUILD b/src/main/java/com/google/devtools/build/lib/BUILD
index faa54bcb36..895ec859d2 100644
--- a/src/main/java/com/google/devtools/build/lib/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/BUILD
@@ -56,6 +56,7 @@ filegroup(
         "//src/main/java/com/google/devtools/build/lib/shell:srcs",
         "//src/main/java/com/google/devtools/build/lib/skyframe/packages:srcs",
         "//src/main/java/com/google/devtools/build/lib/skyframe/serialization:srcs",
+        "//src/main/java/com/google/devtools/build/lib/skylarkbuildapi:srcs",
         "//src/main/java/com/google/devtools/build/lib/skylarkdebug/proto:srcs",
         "//src/main/java/com/google/devtools/build/lib/skylarkinterface/processor:srcs",
         "//src/main/java/com/google/devtools/build/lib/ssd:srcs",
@@ -552,6 +553,7 @@ java_library(
         "//src/main/java/com/google/devtools/build/lib/profiler/memory:current_rule_tracker",
         "//src/main/java/com/google/devtools/build/lib/shell",
         "//src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec",
+        "//src/main/java/com/google/devtools/build/lib/skylarkbuildapi",
         "//src/main/java/com/google/devtools/build/lib/vfs",
         "//src/main/java/com/google/devtools/build/skyframe",
         "//src/main/java/com/google/devtools/build/skyframe:skyframe-objects",
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/BazelBuildApiGlobals.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/BazelBuildApiGlobals.java
new file mode 100644
index 0000000000..efd87e7c10
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/BazelBuildApiGlobals.java
@@ -0,0 +1,47 @@
+// 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.analysis.skylark;
+
+import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkbuildapi.SkylarkBuildApiGlobals;
+import com.google.devtools.build.lib.syntax.Environment;
+import com.google.devtools.build.lib.syntax.EvalException;
+import com.google.devtools.build.lib.syntax.SkylarkUtils;
+
+/**
+ * Bazel implementation of {@link SkylarkBuildApiGlobals}: a collection of global skylark build
+ * API functions that belong in the global namespace.
+ */
+public class BazelBuildApiGlobals implements SkylarkBuildApiGlobals {
+
+  @Override
+  public SkylarkLateBoundDefault<?> configurationField(
+      String fragment, String name, Location loc, Environment env)
+      throws EvalException {
+    Class<?> fragmentClass = SkylarkUtils.getFragmentMap(env).get(fragment);
+
+    if (fragmentClass == null) {
+      throw new EvalException(
+          loc,
+          String.format("invalid configuration fragment name '%s'", fragment));
+    }
+    try {
+      return SkylarkLateBoundDefault.forConfigurationField(
+          fragmentClass, name, SkylarkUtils.getToolsRepository(env));
+    } catch (SkylarkLateBoundDefault.InvalidConfigurationFieldException exception) {
+      throw new EvalException(loc, exception);
+    }
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkLateBoundDefault.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkLateBoundDefault.java
index 93fe96e32e..bf91cafbab 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkLateBoundDefault.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkLateBoundDefault.java
@@ -27,9 +27,9 @@ import com.google.devtools.build.lib.packages.Attribute.LateBoundDefault;
 import com.google.devtools.build.lib.packages.AttributeMap;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
+import com.google.devtools.build.lib.skylarkbuildapi.LateBoundDefaultApi;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
-import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Map;
@@ -50,7 +50,7 @@ import javax.annotation.concurrent.Immutable;
 @Immutable
 @AutoCodec
 public class SkylarkLateBoundDefault<FragmentT> extends AbstractLabelLateBoundDefault<FragmentT>
-    implements SkylarkValue {
+    implements LateBoundDefaultApi {
 
   private final Method method;
   private final String fragmentName;
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkModules.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkModules.java
index 17129ee6f4..a85893197e 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkModules.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkModules.java
@@ -38,8 +38,8 @@ public final class SkylarkModules {
    */
   public static final ImmutableList<Class<?>> MODULES =
       ImmutableList.of(
+          BazelBuildApiGlobals.class,
           SkylarkAttr.class,
-          SkylarkBuildApiGlobals.class,
           SkylarkCommandLine.class,
           SkylarkNativeModule.class,
           SkylarkRuleClassFunctions.class);
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/BUILD b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/BUILD
new file mode 100644
index 0000000000..492daee57e
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/BUILD
@@ -0,0 +1,28 @@
+# Description:
+#   This package contains interfaces representing the skylark "build API"
+#   (but not the implementation of that API). Ultimately, this package
+#   may be broken out of the Bazel package hierarchy to be standalone.
+#   Thus, this package should not depend on Bazel-specific packages (only
+#   those which contain pure-Skylark concepts, such as the interpretter or
+#   annotation interfaces).
+
+package(default_visibility = ["//src/main/java/com/google/devtools/build/lib:__pkg__"])
+
+licenses(["notice"])  # Apache 2.0
+
+filegroup(
+    name = "srcs",
+    srcs = glob(["**"]),
+)
+
+java_library(
+    name = "skylarkbuildapi",
+    srcs = glob(["*.java"]),
+    deps = [
+        "//src/main/java/com/google/devtools/build/lib:events",
+        "//src/main/java/com/google/devtools/build/lib:skylarkinterface",
+        "//src/main/java/com/google/devtools/build/lib:syntax",
+        "//third_party:guava",
+        "//third_party:jsr305",
+    ],
+)
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/LateBoundDefaultApi.java b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/LateBoundDefaultApi.java
new file mode 100644
index 0000000000..080a16f1e3
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/LateBoundDefaultApi.java
@@ -0,0 +1,24 @@
+// 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.skylarkbuildapi;
+
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
+
+/**
+ * The interface for late bound defaults in Skylark.
+ */
+public interface LateBoundDefaultApi extends SkylarkValue {
+  // TODO(cparsons): Migrate this API from the Bazel-specific implementation.
+}
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkBuildApiGlobals.java b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/SkylarkBuildApiGlobals.java
index a8851c92c4..fd24b7ff1e 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkBuildApiGlobals.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/SkylarkBuildApiGlobals.java
@@ -12,8 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package com.google.devtools.build.lib.analysis.skylark;
-
+package com.google.devtools.build.lib.skylarkbuildapi;
 
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.skylarkinterface.Param;
@@ -21,13 +20,12 @@ import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkGlobalLibrary;
 import com.google.devtools.build.lib.syntax.Environment;
 import com.google.devtools.build.lib.syntax.EvalException;
-import com.google.devtools.build.lib.syntax.SkylarkUtils;
 
 /**
  * A collection of global skylark build API functions that belong in the global namespace.
  */
 @SkylarkGlobalLibrary
-public class SkylarkBuildApiGlobals {
+public interface SkylarkBuildApiGlobals {
 
   @SkylarkCallable(
     name = "configuration_field",
@@ -52,21 +50,7 @@ public class SkylarkBuildApiGlobals {
     useLocation = true,
     useEnvironment = true
   )
-  public SkylarkLateBoundDefault<?> configurationField(
+  public LateBoundDefaultApi configurationField(
       String fragment, String name, Location loc, Environment env)
-      throws EvalException {
-    Class<?> fragmentClass = SkylarkUtils.getFragmentMap(env).get(fragment);
-
-    if (fragmentClass == null) {
-      throw new EvalException(
-          loc,
-          String.format("invalid configuration fragment name '%s'", fragment));
-    }
-    try {
-      return SkylarkLateBoundDefault.forConfigurationField(
-          fragmentClass, name, SkylarkUtils.getToolsRepository(env));
-    } catch (SkylarkLateBoundDefault.InvalidConfigurationFieldException exception) {
-      throw new EvalException(loc, exception);
-    }
-  }
+      throws EvalException;
 }
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
index 2c269a74d9..3ee297993a 100644
--- a/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkInterfaceUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkInterfaceUtils.java
@@ -14,6 +14,7 @@
 
 package com.google.devtools.build.lib.skylarkinterface;
 
+import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import javax.annotation.Nullable;
 
@@ -22,30 +23,32 @@ import javax.annotation.Nullable;
  */
 public class SkylarkInterfaceUtils {
 
-  private static final class ClassAndSkylarkModule {
+  private static final class ClassWithAnnotation<T extends Annotation> {
     final Class<?> klass;
-    final SkylarkModule skylarkModule;
+    final T annotation;
 
-    ClassAndSkylarkModule(Class<?> klass, SkylarkModule skylarkModule) {
+    ClassWithAnnotation(Class<?> klass, T annotation) {
       this.klass = klass;
-      this.skylarkModule = skylarkModule;
+      this.annotation = annotation;
     }
   }
 
   @Nullable
-  private static ClassAndSkylarkModule searchForSkylarkModule(Class<?> classObj) {
-    if (classObj.isAnnotationPresent(SkylarkModule.class)) {
-      return new ClassAndSkylarkModule(classObj, classObj.getAnnotation(SkylarkModule.class));
+  private static <T extends Annotation> ClassWithAnnotation<T> searchForClassAnnotation(
+      Class<?> classObj,
+      Class<T> annotationClass) {
+    if (classObj.isAnnotationPresent(annotationClass)) {
+      return new ClassWithAnnotation<T>(classObj, classObj.getAnnotation(annotationClass));
     }
     Class<?> superclass = classObj.getSuperclass();
     if (superclass != null) {
-      ClassAndSkylarkModule result = searchForSkylarkModule(superclass);
+      ClassWithAnnotation<T> result = searchForClassAnnotation(superclass, annotationClass);
       if (result != null) {
         return result;
       }
     }
     for (Class<?> interfaceObj : classObj.getInterfaces()) {
-      ClassAndSkylarkModule result = searchForSkylarkModule(interfaceObj);
+      ClassWithAnnotation<T> result = searchForClassAnnotation(interfaceObj, annotationClass);
       if (result != null) {
         return result;
       }
@@ -60,8 +63,9 @@ public class SkylarkInterfaceUtils {
    */
   @Nullable
   public static SkylarkModule getSkylarkModule(Class<?> classObj) {
-    ClassAndSkylarkModule result = searchForSkylarkModule(classObj);
-    return result == null ? null : result.skylarkModule;
+    ClassWithAnnotation<SkylarkModule> result =
+        searchForClassAnnotation(classObj, SkylarkModule.class);
+    return result == null ? null : result.annotation;
   }
 
   /**
@@ -71,11 +75,23 @@ public class SkylarkInterfaceUtils {
    */
   @Nullable
   public static Class<?> getParentWithSkylarkModule(Class<?> classObj) {
-    ClassAndSkylarkModule result = searchForSkylarkModule(classObj);
+    ClassWithAnnotation<SkylarkModule> result =
+        searchForClassAnnotation(classObj, SkylarkModule.class);
     return result == null ? null : result.klass;
   }
 
   /**
+   * Searches {@code classObj}'s class hierarchy and for a superclass or interface that
+   * is annotated with {@link SkylarkGlobalLibrary} (including possibly {@code classObj} itself),
+   * and returns true if one is found.
+   */
+  public static boolean hasSkylarkGlobalLibrary(Class<?> classObj) {
+    ClassWithAnnotation<SkylarkGlobalLibrary> result =
+        searchForClassAnnotation(classObj, SkylarkGlobalLibrary.class);
+    return result != null;
+  }
+
+  /**
    * Returns the {@link SkylarkCallable} annotation for the given method, if it exists, and
    * null otherwise. 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
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Runtime.java b/src/main/java/com/google/devtools/build/lib/syntax/Runtime.java
index c037db2781..86f95b38b7 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Runtime.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Runtime.java
@@ -19,6 +19,7 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkGlobalLibrary;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkInterfaceUtils;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
@@ -337,14 +338,19 @@ public final class Runtime {
    *       callables.</li>
    * </ul>
    *
+   * <p>On collisions, this method throws an {@link AssertionError}. Collisions may occur if
+   * multiple global libraries have functions of the same name, two modules of the same name
+   * are given, or if two subclasses of the same module are given.
+   *
    * @param env the Environment into which to register fields.
    * @param moduleClass the Class object containing globals.
    */
   public static void setupModuleGlobals(Environment env, Class<?> moduleClass) {
     try {
-      if (moduleClass.isAnnotationPresent(SkylarkModule.class)) {
+      SkylarkModule skylarkModule = SkylarkInterfaceUtils.getSkylarkModule(moduleClass);
+      if (skylarkModule != null) {
         env.setup(
-            moduleClass.getAnnotation(SkylarkModule.class).name(),
+            skylarkModule.name(),
             moduleClass.getConstructor().newInstance());
       }
       for (Field field : moduleClass.getDeclaredFields()) {
@@ -362,7 +368,7 @@ public final class Runtime {
           }
         }
       }
-      if (moduleClass.isAnnotationPresent(SkylarkGlobalLibrary.class)) {
+      if (SkylarkInterfaceUtils.hasSkylarkGlobalLibrary(moduleClass)) {
         Object moduleInstance = moduleClass.getConstructor().newInstance();
         for (String methodName : FuncallExpression.getMethodNames(moduleClass)) {
           env.setup(methodName, FuncallExpression.getBuiltinCallable(moduleInstance, methodName));