Make source jars from java_library available to Skylark.

This is necessary to implement GWT support in Bazel, which requires source jars
on the classpath. With this change, I can build a GWT classpath as follows:

  all_deps = ctx.files.deps
  for this_dep in ctx.attr.deps:
    if this_dep.java: all_deps += this_dep.java.source_jars
  classpath = ":".join([dep.path for dep in all_deps])

--
Change-Id: I1983cb57f15eb48e49b81b250bb18bb51b7d9391
Reviewed-on: https://bazel-review.googlesource.com/1441
MOS_MIGRATED_REVID=95111144

2 files changed, 54 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaLibrary.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaLibrary.java
index 68f5ccd942..c2ced5912a 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaLibrary.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaLibrary.java
@@ -223,6 +223,7 @@ public class JavaLibrary implements RuleConfiguredTargetFactory {
             new JavaRuntimeJarProvider(common.getJavaCompilationArtifacts().getRuntimeJars()))
         .add(RunfilesProvider.class, RunfilesProvider.simple(runfiles))
         .setFilesToBuild(filesToBuild)
+        .addSkylarkTransitiveInfo(JavaSkylarkApiProvider.NAME, new JavaSkylarkApiProvider())
         .add(JavaNeverlinkInfoProvider.class, new JavaNeverlinkInfoProvider(neverLink))
         .add(CppCompilationContext.class, transitiveCppDeps)
         .add(JavaCompilationArgsProvider.class, new JavaCompilationArgsProvider(
diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaSkylarkApiProvider.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaSkylarkApiProvider.java
new file mode 100644
index 0000000000..4c2122314f
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaSkylarkApiProvider.java
@@ -0,0 +1,53 @@
+// Copyright 2015 Google Inc. 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.rules.java;
+
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.rules.SkylarkApiProvider;
+import com.google.devtools.build.lib.syntax.SkylarkCallable;
+import com.google.devtools.build.lib.syntax.SkylarkModule;
+
+/**
+ * A class that exposes the Java providers to Skylark. It is intended to provide a
+ * simple and stable interface for Skylark users.
+ */
+@SkylarkModule(
+    name = "JavaSkylarkApiProvider", doc = "Provides access to information about Java rules")
+public final class JavaSkylarkApiProvider extends SkylarkApiProvider {
+  /** The name of the field in Skylark used to access this class. */
+  static final String NAME = "java";
+
+  @SkylarkCallable(
+      name = "source_jars",
+      doc = "Returns the Jars containing Java source files for the target",
+      structField = true)
+  public ImmutableList<Artifact> getSourceJars() {
+    JavaSourceJarsProvider sourceJars = getInfo().getProvider(JavaSourceJarsProvider.class);
+    return sourceJars.getSourceJars();
+  }
+
+  @SkylarkCallable(
+      name = "transitive_source_jars",
+      doc =
+          "Returns the Jars containing Java source files for the target and all of its transitive "
+              + "dependencies",
+      structField = true)
+  public NestedSet<Artifact> getTransitiveSourceJars() {
+    JavaSourceJarsProvider sourceJars = getInfo().getProvider(JavaSourceJarsProvider.class);
+    return sourceJars.getTransitiveSourceJars();
+  }
+}