Create BootClassPathCachingFileManager a subclass of JavacFileManager…

… which handles caching for the boot classpaths. The class also decides if an instance can be kept for the current compilation or needs to be updated (e.g., if a bootclasspath digest has changed)

Note: BootClassPathCachingFileManager is used only with singleplex-workers that have list of boot classpaths along with their digest information.

RELNOTES: None.
PiperOrigin-RevId: 387592935

src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BUILD

@@ -42,11 +42,15 @@ JAVAC_OPTIONS_SRCS = [
  "javac/WerrorCustomOption.java",
 ]
 
+JAVAC_TEST_SRCS = [
+ "javac/BootClassPathCachingFileManagerTest.java",
+]
+
 java_library(
  name = "javac",
  srcs = glob(
  ["javac/*.java"],
- exclude = JAVAC_OPTIONS_SRCS,
+ exclude = JAVAC_OPTIONS_SRCS + JAVAC_TEST_SRCS,
  ),
  deps = [
  ":invalid_command_line_exception",
@@ -204,3 +208,16 @@ bootstrap_java_binary(
  "//src/java_tools/buildjar/java/com/google/devtools/build/buildjar/jarhelper:bootstrap_jarhelper",
  ],
 )
+
+java_test(
+ name = "BootClassPathCachingFileManagerTest",
+ srcs = ["javac/BootClassPathCachingFileManagerTest.java"],
+ deps = [
+ ":javac",
+ "//third_party:guava",
+ "//third_party:junit4",
+ "//third_party:truth",
+ "//third_party/java/jdk/langtools:javac",
+ "//third_party/protobuf:protobuf_java",
+ ],
+)

src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/BlazeJavacMain.java

@@ -50,8 +50,11 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
+import java.util.Set;
 import javax.tools.Diagnostic;
 import javax.tools.DiagnosticListener;
+import javax.tools.JavaFileObject;
+import javax.tools.JavaFileObject.Kind;
 import javax.tools.StandardLocation;
 
 /**
@@ -109,6 +112,11 @@ public static BlazeJavacResult compile(BlazeJavacArguments arguments) {
  try (JavacFileManager fileManager =
  new ClassloaderMaskingFileManager(context, arguments.builtinProcessors())) {
 
+ bootFileManager = getBootFileManager(arguments);
+ if (bootFileManager != null) {
+ setLocations(bootFileManager, arguments);
+ }
+
  setLocations(fileManager, arguments);
 
  JavacTask task =
@@ -305,6 +313,32 @@ private static void setLocations(JavacFileManager fileManager, BlazeJavacArgumen
  }
  }
 
+ /** a javac file manager instance specific only for boot classpaths */
+ private static BootClassPathCachingFileManager bootFileManager;
+
+ /**
+ * Returns a BootClassPathCachingFileManager instance if it is a singleplex-worker with valid
+ * arguments
+ */
+ private static BootClassPathCachingFileManager getBootFileManager(BlazeJavacArguments arguments) {
+
+ if (!arguments.requestId().isPresent()) {
+ // worker mode is not enabled
+ return null;
+ }
+ if (arguments.requestId().getAsInt() != 0) {
+ // worker is not singleplex worker
+ return null;
+ }
+ if (!BootClassPathCachingFileManager.areArgumentsValid(arguments)) {
+ return null;
+ }
+
+ return (bootFileManager != null && !bootFileManager.needsUpdate(arguments))
+ ? bootFileManager
+ : new BootClassPathCachingFileManager(new Context(), arguments);
+ }
+
  /**
  * 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
@@ -321,6 +355,16 @@ public ClassloaderMaskingFileManager(Context context, ImmutableSet<String> built
  this.builtinProcessors = builtinProcessors;
  }
 
+ @Override
+ public Iterable<JavaFileObject> list(
+ Location location, String packageName, Set<Kind> kinds, boolean recurse)
+ throws IOException {
+ if (bootFileManager != null && location == StandardLocation.PLATFORM_CLASS_PATH) {
+ return bootFileManager.list(location, packageName, kinds, recurse);
+ }
+ return super.list(location, packageName, kinds, recurse);
+ }
+
  @Override
  protected ClassLoader getClassLoader(URL[] urls) {
  return new URLClassLoader(

src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/BootClassPathCachingFileManager.java

@@ -0,0 +1,85 @@
+// Copyright 2021 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;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.protobuf.ByteString;
+import com.sun.tools.javac.file.JavacFileManager;
+import com.sun.tools.javac.util.Context;
+import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
+
+/** A subclass of the JavacFileManager that handles only boot classpaths */
+@VisibleForTesting
+class BootClassPathCachingFileManager extends JavacFileManager {
+
+ private final Map<String, ByteString> bootJarsAndDigest = new HashMap<>();
+
+ /** Create a JavacFileManager using a given context and BlazeJavacArguments */
+ public BootClassPathCachingFileManager(Context context, BlazeJavacArguments arguments) {
+ super(context, false, UTF_8);
+
+ for (Path bootClassPath : arguments.bootClassPath()) {
+ bootJarsAndDigest.put(
+ bootClassPath.toString(), arguments.inputsAndDigest().get(bootClassPath.toString()));
+ }
+ }
+
+ /**
+ * Checks if this instance or a new instance is needed for the {@code BlazeJavacArguments}. An
+ * update is needed if the bootclasspath in {@code BlazeJavacArguments} have changed its digest.
+ */
+ @VisibleForTesting
+ boolean needsUpdate(BlazeJavacArguments arguments) {
+ for (Path bootClassPath : arguments.bootClassPath()) {
+ ByteString currDigest = arguments.inputsAndDigest().get(bootClassPath.toString());
+
+ if (currDigest == null) {
+ return true;
+ }
+
+ ByteString oldDigest = bootJarsAndDigest.putIfAbsent(bootClassPath.toString(), currDigest);
+
+ if (oldDigest != null && !oldDigest.equals(currDigest)) {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Checks if the bootClassPaths in {@code BlazeJavacArguments} can benefit from the {@code
+ * BootCachingFileManager}. Arguments are not valid if missing boot classpath or at least one
+ * digest
+ */
+ @VisibleForTesting
+ static boolean areArgumentsValid(BlazeJavacArguments arguments) {
+ if (arguments.bootClassPath().isEmpty()) {
+ return false;
+ }
+
+ for (Path bootClassPath : arguments.bootClassPath()) {
+ ByteString currDigest = arguments.inputsAndDigest().get(bootClassPath.toString());
+ if (currDigest == null) {
+ return false;
+ }
+ }
+
+ return true;
+ }
+}

src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/BootClassPathCachingFileManagerTest.java

@@ -0,0 +1,168 @@
+// Copyright 2021 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;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.protobuf.ByteString;
+import com.sun.tools.javac.util.Context;
+import java.io.IOException;
+import java.nio.file.Path;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** {@link BootClassPathCachingFileManager}Test */
+@RunWith(JUnit4.class)
+public class BootClassPathCachingFileManagerTest {
+ private ImmutableList<Path> bootClassPathsCandidates;
+ private BootClassPathCachingFileManager bootFileManager;
+
+ @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+ @Before
+ public void createBootFileManager() throws IOException {
+ bootClassPathsCandidates =
+ ImmutableList.of(
+ temporaryFolder.newFolder().toPath().resolve("BootClassPath0.jar"),
+ temporaryFolder.newFolder().toPath().resolve("BootClassPath1.jar"),
+ temporaryFolder.newFolder().toPath().resolve("BootClassPath2.jar"));
+
+ ImmutableList<Path> bootClassPaths =
+ ImmutableList.of(bootClassPathsCandidates.get(0), bootClassPathsCandidates.get(1));
+
+ ImmutableMap<String, ByteString> inputsAndDigest =
+ ImmutableMap.<String, ByteString>builder()
+ .put(
+ bootClassPaths.get(0).toString(),
+ ByteString.copyFromUtf8(bootClassPaths.get(0).toString()))
+ .put(
+ bootClassPaths.get(1).toString(),
+ ByteString.copyFromUtf8(bootClassPaths.get(1).toString()))
+ .build();
+
+ BlazeJavacArguments arguments =
+ BlazeJavacArguments.builder()
+ .bootClassPath(bootClassPaths)
+ .inputsAndDigest(inputsAndDigest)
+ .classOutput(temporaryFolder.newFolder().toPath().resolve("output_0.jar"))
+ .build();
+
+ bootFileManager = new BootClassPathCachingFileManager(new Context(), arguments);
+ }
+
+ @Test
+ public void testNeedsUpdate() throws IOException {
+ ImmutableList<Path> bootClassPaths =
+ ImmutableList.of(
+ bootClassPathsCandidates.get(0),
+ bootClassPathsCandidates.get(1),
+ bootClassPathsCandidates.get(2));
+
+ ImmutableMap<String, ByteString> inputsAndDigest =
+ ImmutableMap.<String, ByteString>builder()
+ .put(
+ bootClassPaths.get(0).toString(),
+ ByteString.copyFromUtf8(bootClassPaths.get(0).toString()))
+ .put(
+ bootClassPaths.get(1).toString(),
+ ByteString.copyFromUtf8(bootClassPaths.get(1).toString()))
+ .put(
+ bootClassPaths.get(2).toString(),
+ ByteString.copyFromUtf8(bootClassPaths.get(2).toString()))
+ .build();
+
+ BlazeJavacArguments arguments =
+ BlazeJavacArguments.builder()
+ .bootClassPath(bootClassPaths)
+ .inputsAndDigest(inputsAndDigest)
+ .classOutput(temporaryFolder.newFolder().toPath().resolve("output_1.jar"))
+ .build();
+
+ assertThat(bootFileManager.needsUpdate(arguments)).isFalse();
+ }
+
+ @Test
+ public void testNeedsUpdate_withDifferentDigest() throws IOException {
+ ImmutableList<Path> bootClassPaths =
+ ImmutableList.of(bootClassPathsCandidates.get(0), bootClassPathsCandidates.get(1));
+
+ ImmutableMap<String, ByteString> inputsAndDigest =
+ ImmutableMap.<String, ByteString>builder()
+ .put(bootClassPaths.get(0).toString(), ByteString.copyFromUtf8("different digest"))
+ .put(
+ bootClassPaths.get(1).toString(),
+ ByteString.copyFromUtf8(bootClassPaths.get(1).toString()))
+ .build();
+
+ BlazeJavacArguments arguments =
+ BlazeJavacArguments.builder()
+ .bootClassPath(bootClassPaths)
+ .inputsAndDigest(inputsAndDigest)
+ .classOutput(temporaryFolder.newFolder().toPath().resolve("output_1.jar"))
+ .build();
+
+ assertThat(bootFileManager.needsUpdate(arguments)).isTrue();
+ }
+
+ @Test
+ public void testAreArgumentsValid_withOneMissingDigest() throws IOException {
+ ImmutableList<Path> bootClassPaths =
+ ImmutableList.of(bootClassPathsCandidates.get(0), bootClassPathsCandidates.get(1));
+
+ ImmutableMap<String, ByteString> inputsAndDigest =
+ ImmutableMap.of(
+ bootClassPaths.get(1).toString(),
+ ByteString.copyFromUtf8(bootClassPaths.get(1).toString()));
+
+ BlazeJavacArguments arguments =
+ BlazeJavacArguments.builder()
+ .bootClassPath(bootClassPaths)
+ .inputsAndDigest(inputsAndDigest)
+ .classOutput(temporaryFolder.newFolder().toPath().resolve("output_1.jar"))
+ .build();
+
+ assertThat(BootClassPathCachingFileManager.areArgumentsValid(arguments)).isFalse();
+ }
+
+ @Test
+ public void testAreArgumentsValid_withEmptyInputsAndDigest() throws IOException {
+ ImmutableList<Path> bootClassPaths =
+ ImmutableList.of(bootClassPathsCandidates.get(0), bootClassPathsCandidates.get(1));
+
+ BlazeJavacArguments arguments =
+ BlazeJavacArguments.builder()
+ .bootClassPath(bootClassPaths)
+ .classOutput(temporaryFolder.newFolder().toPath().resolve("output_1.jar"))
+ .build();
+
+ assertThat(BootClassPathCachingFileManager.areArgumentsValid(arguments)).isFalse();
+ }
+
+ @Test
+ public void testAreArgumentsValid_withEmptyBootClassPaths() throws IOException {
+ assertThat(
+ BootClassPathCachingFileManager.areArgumentsValid(
+ BlazeJavacArguments.builder()
+ .classOutput(temporaryFolder.newFolder().toPath().resolve("output_1.jar"))
+ .build()))
+ .isFalse();
+ }
+}