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// Copyright 2014 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.buildjar;
import com.google.devtools.build.buildjar.javac.JavacRunner;
import com.sun.tools.javac.main.Main.Result;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.regex.Pattern;
/**
* A variant of SimpleJavaLibraryBuilder that attempts to reduce the compile-time classpath right
* before invoking the compiler, based on extra information from provided .jdeps files. This mode is
* enabled via the --reduce_classpath flag, only when Blaze runs with --experimental_java_classpath.
*
* <p>A fall-back mechanism detects whether javac fails because the classpath is incorrectly
* discarding required entries, and re-attempts to compile with the full classpath.
*/
public class ReducedClasspathJavaLibraryBuilder extends SimpleJavaLibraryBuilder {
/**
* Attempts to minimize the compile-time classpath before invoking javac, falling back to a
* regular compile.
*
* @param build A JavaLibraryBuildRequest request object describing what to compile
* @return result code of the javac compilation
* @throws IOException clean-up up the output directory fails
*/
@Override
Result compileSources(JavaLibraryBuildRequest build, JavacRunner javacRunner, PrintWriter err)
throws IOException {
// Minimize classpath, but only if we're actually compiling some sources (some invocations of
// JavaBuilder are only building resource jars).
String compressedClasspath = build.getClassPath();
if (!build.getSourceFiles().isEmpty()) {
compressedClasspath = build.getDependencyModule()
.computeStrictClasspath(build.getClassPath(), build.getClassDir());
}
String[] javacArguments = makeJavacArguments(build, compressedClasspath);
// Compile!
StringWriter javacOutput = new StringWriter();
PrintWriter javacOutputWriter = new PrintWriter(javacOutput);
Result result = javacRunner.invokeJavac(javacArguments, javacOutputWriter);
javacOutputWriter.close();
// If javac errored out because of missing entries on the classpath, give it another try.
// TODO(bazel-team): check performance impact of additional retries.
if (!result.isOK() && hasRecognizedError(javacOutput.toString())) {
if (debug) {
err.println("warning: [transitive] Target uses transitive classpath to compile.");
}
// Reset output directories
prepareSourceCompilation(build);
// Fall back to the regular compile, but add extra checks to catch transitive uses
javacArguments = makeJavacArguments(build);
result = javacRunner.invokeJavac(javacArguments, err);
} else {
err.print(javacOutput.getBuffer());
}
return result;
}
private static final Pattern MISSING_PACKAGE =
Pattern.compile("error: package ([\\p{javaJavaIdentifierPart}\\.]+) does not exist");
private boolean hasRecognizedError(String javacOutput) {
return javacOutput.contains("error: cannot access")
|| javacOutput.contains("error: cannot find symbol")
|| javacOutput.contains("com.sun.tools.javac.code.Symbol$CompletionFailure")
|| MISSING_PACKAGE.matcher(javacOutput).find();
}
}
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