Use an isolated classloader for JavaBuilder plugins

--
MOS_MIGRATED_REVID=104131197

3 files changed, 68 insertions, 33 deletions

diff --git a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java
index 6d8b2530ff..ebb0e7cd0f 100644
--- a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java
+++ b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java
@@ -17,9 +17,9 @@ package com.google.devtools.build.buildjar;
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.buildjar.javac.JavacOptions;
 import com.google.devtools.build.buildjar.javac.plugins.BlazeJavaCompilerPlugin;
+import com.google.devtools.build.buildjar.javac.plugins.classloader.ClassLoaderMaskingPlugin;
 import com.google.devtools.build.buildjar.javac.plugins.dependency.DependencyModule;
 import com.google.devtools.build.buildjar.javac.plugins.errorprone.ErrorPronePlugin;
-import com.google.devtools.build.buildjar.javac.plugins.filemanager.FileManagerInitializationPlugin;
 import com.google.devtools.build.lib.worker.WorkerProtocol.WorkRequest;
 import com.google.devtools.build.lib.worker.WorkerProtocol.WorkResponse;
 
@@ -124,7 +124,7 @@ public abstract class BazelJavaBuilder {
       InvalidCommandLineException {
     ImmutableList<BlazeJavaCompilerPlugin> plugins =
         ImmutableList.<BlazeJavaCompilerPlugin>of(
-            new FileManagerInitializationPlugin(),
+            new ClassLoaderMaskingPlugin(),
             new ErrorPronePlugin());
     JavaLibraryBuildRequest build =
         new JavaLibraryBuildRequest(args, plugins, new DependencyModule.Builder());
diff --git a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/classloader/ClassLoaderMaskingPlugin.java b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/classloader/ClassLoaderMaskingPlugin.java
new file mode 100644
index 0000000000..59e2b9ec90
--- /dev/null
+++ b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/classloader/ClassLoaderMaskingPlugin.java
@@ -0,0 +1,66 @@
+// Copyright 2015 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.buildjar.javac.plugins.classloader;
+ 
+import com.google.devtools.build.buildjar.javac.plugins.BlazeJavaCompilerPlugin;
+
+import com.sun.tools.javac.file.JavacFileManager;
+import com.sun.tools.javac.util.Context;
+
+import java.net.URL;
+import java.net.URLClassLoader;
+
+import javax.tools.JavaFileManager;
+
+/** A plugin that customizes the Java compiler for the Error Prone plugin. */
+public final class ClassLoaderMaskingPlugin extends BlazeJavaCompilerPlugin {
+
+  @Override
+  public void initializeContext(Context context) {
+    context.put(JavaFileManager.class, new Context.Factory<JavaFileManager>() {
+      @Override
+      public JavaFileManager make(Context c) {
+        return new JavacFileManager(c, true, null) {
+          @Override
+          protected ClassLoader getClassLoader(URL[] urls) {
+            return new URLClassLoader(urls, makeMaskedClassLoader());
+          }
+        };
+      }
+    });
+    super.initializeContext(context);
+  }
+
+  /**
+   * When Bazel invokes JavaBuilder, it puts javac.jar on the bootstrap class path and
+   * JavaBuilder_deploy.jar on the user class path. We need Error Prone to be
+   * available on the annotation processor path, but we want to mask out any other
+   * classes to minimize class version skew.
+   */
+  private ClassLoader makeMaskedClassLoader() {
+    return new ClassLoader(JavacFileManager.class.getClassLoader()) {
+      @Override
+      protected Class<?> findClass(String name) throws ClassNotFoundException {
+        if (name.startsWith("com.google.errorprone.")) {
+          return Class.forName(name);
+        } else if (name.startsWith("org.checkerframework.dataflow.")) {
+          return Class.forName(name);
+        } else {
+          throw new ClassNotFoundException(name);
+        }
+      }
+    };
+  }
+}
diff --git a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/filemanager/FileManagerInitializationPlugin.java b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/filemanager/FileManagerInitializationPlugin.java
deleted file mode 100644
index 1cb4b36085..0000000000
--- a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/filemanager/FileManagerInitializationPlugin.java
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright 2014 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.buildjar.javac.plugins.filemanager;
-
-import com.google.devtools.build.buildjar.javac.plugins.BlazeJavaCompilerPlugin;
-
-import com.sun.tools.javac.file.JavacFileManager;
-import com.sun.tools.javac.util.Context;
-
-/**
- * Register a context factory to create JavacFileManagers.
- */
-public class FileManagerInitializationPlugin extends BlazeJavaCompilerPlugin {
-
-  @Override
-  public void initializeContext(Context context) {
-    JavacFileManager.preRegister(context);
-  }
-}