com.google.googlejavaformat.java.filer.FormattingJavaFileObject.java Source code

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Here is the source code for com.google.googlejavaformat.java.filer.FormattingJavaFileObject.java

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/*
 * Copyright 2016 Google Inc.
 *
 * 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.googlejavaformat.java.filer;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.io.CharSink;
import com.google.common.io.CharSource;
import com.google.googlejavaformat.java.Formatter;
import com.google.googlejavaformat.java.FormatterException;
import java.io.IOException;
import java.io.Writer;
import javax.annotation.Nullable;
import javax.annotation.processing.Messager;
import javax.tools.Diagnostic;
import javax.tools.ForwardingJavaFileObject;
import javax.tools.JavaFileObject;

/** A {@link JavaFileObject} decorator which {@linkplain Formatter formats} source code. */
final class FormattingJavaFileObject extends ForwardingJavaFileObject<JavaFileObject> {
    /** A rough estimate of the average file size: 80 chars per line, 500 lines. */
    private static final int DEFAULT_FILE_SIZE = 80 * 500;

    private final Formatter formatter;
    private final Messager messager;

    /**
     * Create a new {@link FormattingJavaFileObject}.
     *
     * @param delegate {@link JavaFileObject} to decorate
     * @param messager to log messages with.
     */
    FormattingJavaFileObject(JavaFileObject delegate, Formatter formatter, @Nullable Messager messager) {
        super(checkNotNull(delegate));
        this.formatter = checkNotNull(formatter);
        this.messager = messager;
    }

    @Override
    public Writer openWriter() throws IOException {
        final StringBuilder stringBuilder = new StringBuilder(DEFAULT_FILE_SIZE);
        return new Writer() {
            @Override
            public void write(char[] chars, int start, int end) throws IOException {
                stringBuilder.append(chars, start, end - start);
            }

            @Override
            public void write(String string) throws IOException {
                stringBuilder.append(string);
            }

            @Override
            public void flush() throws IOException {
            }

            @Override
            public void close() throws IOException {
                try {
                    formatter.formatSource(CharSource.wrap(stringBuilder), new CharSink() {
                        @Override
                        public Writer openStream() throws IOException {
                            return fileObject.openWriter();
                        }
                    });
                } catch (FormatterException e) {
                    // An exception will happen when the code being formatted has an error. It's better to
                    // log the exception and emit unformatted code so the developer can view the code which
                    // caused a problem.
                    try (Writer writer = fileObject.openWriter()) {
                        writer.append(stringBuilder.toString());
                    }
                    if (messager != null) {
                        messager.printMessage(Diagnostic.Kind.NOTE, "Error formatting " + getName());
                    }
                }
            }
        };
    }
}