core/src/main/java/com/google/googlejavaformat/java/Formatter.java

/*
 * Copyright 2015 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;

import static com.google.common.base.StandardSystemProperty.JAVA_CLASS_VERSION;
import static com.google.common.base.StandardSystemProperty.JAVA_SPECIFICATION_VERSION;
import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Iterators;
import com.google.common.collect.Range;
import com.google.common.collect.RangeSet;
import com.google.common.collect.TreeRangeSet;
import com.google.common.io.CharSink;
import com.google.common.io.CharSource;
import com.google.errorprone.annotations.Immutable;
import com.google.googlejavaformat.Doc;
import com.google.googlejavaformat.DocBuilder;
import com.google.googlejavaformat.FormattingError;
import com.google.googlejavaformat.Newlines;
import com.google.googlejavaformat.Op;
import com.google.googlejavaformat.OpsBuilder;
import com.sun.tools.javac.file.JavacFileManager;
import com.sun.tools.javac.parser.JavacParser;
import com.sun.tools.javac.parser.ParserFactory;
import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.Log;
import com.sun.tools.javac.util.Options;
import java.io.IOError;
import java.io.IOException;
import java.lang.reflect.Method;
import java.net.URI;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.DiagnosticListener;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import javax.tools.StandardLocation;

/**
 * This is google-java-format, a new Java formatter that follows the Google Java Style Guide quite
 * precisely---to the letter and to the spirit.
 *
 * <p>This formatter uses the javac parser to generate an AST. Because the AST loses information
 * about the non-tokens in the input (including newlines, comments, etc.), and even some tokens
 * (e.g., optional commas or semicolons), this formatter lexes the input again and follows along in
 * the resulting list of tokens. Its lexer splits all multi-character operators (like "&gt;&gt;")
 * into multiple single-character operators. Each non-token is assigned to a token---non-tokens
 * following a token on the same line go with that token; those following go with the next token---
 * and there is a final EOF token to hold final comments.
 *
 * <p>The formatter walks the AST to generate a Greg Nelson/Derek Oppen-style list of formatting
 * {@link Op}s [1--2] that then generates a structured {@link Doc}. Each AST node type has a visitor
 * to emit a sequence of {@link Op}s for the node.
 *
 * <p>Some data-structure operations are easier in the list of {@link Op}s, while others become
 * easier in the {@link Doc}. The {@link Op}s are walked to attach the comments. As the {@link Op}s
 * are generated, missing input tokens are inserted and incorrect output tokens are dropped,
 * ensuring that the output matches the input even in the face of formatter errors. Finally, the
 * formatter walks the {@link Doc} to format it in the given width.
 *
 * <p>This formatter also produces data structures of which tokens and comments appear where on the
 * input, and on the output, to help output a partial reformatting of a slightly edited input.
 *
 * <p>Instances of the formatter are immutable and thread-safe.
 *
 * <p>[1] Nelson, Greg, and John DeTreville. Personal communication.
 *
 * <p>[2] Oppen, Derek C. "Prettyprinting". ACM Transactions on Programming Languages and Systems,
 * Volume 2 Issue 4, Oct. 1980, pp. 465–483.
 */
@Immutable
public final class Formatter {

  public static final int MAX_LINE_LENGTH = 100;

  static final Range<Integer> EMPTY_RANGE = Range.closedOpen(-1, -1);

  private final JavaFormatterOptions options;

  /** A new Formatter instance with default options. */
  public Formatter() {
    this(JavaFormatterOptions.defaultOptions());
  }

  public Formatter(JavaFormatterOptions options) {
    this.options = options;
  }

  /**
   * Construct a {@code Formatter} given a Java compilation unit. Parses the code; builds a {@link
   * JavaInput} and the corresponding {@link JavaOutput}.
   *
   * @param javaInput the input, a Java compilation unit
   * @param javaOutput the {@link JavaOutput}
   * @param options the {@link JavaFormatterOptions}
   */
  static void format(final JavaInput javaInput, JavaOutput javaOutput, JavaFormatterOptions options)
      throws FormatterException {
    Context context = new Context();
    DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
    context.put(DiagnosticListener.class, diagnostics);
    Options.instance(context).put("allowStringFolding", "false");
    Options.instance(context).put("--enable-preview", "true");
    JCCompilationUnit unit;
    JavacFileManager fileManager = new JavacFileManager(context, true, UTF_8);
    try {
      fileManager.setLocation(StandardLocation.PLATFORM_CLASS_PATH, ImmutableList.of());
    } catch (IOException e) {
      // impossible
      throw new IOError(e);
    }
    SimpleJavaFileObject source =
        new SimpleJavaFileObject(URI.create("source"), JavaFileObject.Kind.SOURCE) {
          @Override
          public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
            return javaInput.getText();
          }
        };
    Log.instance(context).useSource(source);
    ParserFactory parserFactory = ParserFactory.instance(context);
    JavacParser parser =
        parserFactory.newParser(
            javaInput.getText(),
            /*keepDocComments=*/ true,
            /*keepEndPos=*/ true,
            /*keepLineMap=*/ true);
    unit = parser.parseCompilationUnit();
    unit.sourcefile = source;

    javaInput.setCompilationUnit(unit);
    Iterable<Diagnostic<? extends JavaFileObject>> errorDiagnostics =
        Iterables.filter(diagnostics.getDiagnostics(), Formatter::errorDiagnostic);
    if (!Iterables.isEmpty(errorDiagnostics)) {
      throw FormatterException.fromJavacDiagnostics(errorDiagnostics);
    }
    OpsBuilder builder = new OpsBuilder(javaInput, javaOutput);
    // Output the compilation unit.
    JavaInputAstVisitor visitor;
    if (getMajor() >= 14) {
      try {
        visitor =
            Class.forName("com.google.googlejavaformat.java.java14.Java14InputAstVisitor")
                .asSubclass(JavaInputAstVisitor.class)
                .getConstructor(OpsBuilder.class, int.class)
                .newInstance(builder, options.indentationMultiplier());
      } catch (ReflectiveOperationException e) {
        throw new LinkageError(e.getMessage(), e);
      }
    } else {
      visitor = new JavaInputAstVisitor(builder, options.indentationMultiplier());
    }
    visitor.scan(unit, null);
    builder.sync(javaInput.getText().length());
    builder.drain();
    Doc doc = new DocBuilder().withOps(builder.build()).build();
    doc.computeBreaks(javaOutput.getCommentsHelper(), MAX_LINE_LENGTH, new Doc.State(+0, 0));
    doc.write(javaOutput);
    javaOutput.flush();
  }

  // Runtime.Version was added in JDK 9, so use reflection to access it to preserve source
  // compatibility with Java 8.
  private static int getMajor() {
    try {
      Method versionMethod = Runtime.class.getMethod("version");
      Object version = versionMethod.invoke(null);
      return (int) version.getClass().getMethod("major").invoke(version);
    } catch (Exception e) {
      // continue below
    }
    int version = (int) Double.parseDouble(JAVA_CLASS_VERSION.value());
    if (49 <= version && version <= 52) {
      return version - (49 - 5);
    }
    throw new IllegalStateException("Unknown Java version: " + JAVA_SPECIFICATION_VERSION.value());
  }

  static boolean errorDiagnostic(Diagnostic<?> input) {
    if (input.getKind() != Diagnostic.Kind.ERROR) {
      return false;
    }
    switch (input.getCode()) {
      case "compiler.err.invalid.meth.decl.ret.type.req":
        // accept constructor-like method declarations that don't match the name of their
        // enclosing class
        return false;
      default:
        break;
    }
    return true;
  }

  /**
   * Format the given input (a Java compilation unit) into the output stream.
   *
   * @throws FormatterException if the input cannot be parsed
   */
  public void formatSource(CharSource input, CharSink output)
      throws FormatterException, IOException {
    // TODO(cushon): proper support for streaming input/output. Input may
    // not be feasible (parsing) but output should be easier.
    output.write(formatSource(input.read()));
  }

  /**
   * Format an input string (a Java compilation unit) into an output string.
   *
   * <p>Leaves import statements untouched.
   *
   * @param input the input string
   * @return the output string
   * @throws FormatterException if the input string cannot be parsed
   */
  public String formatSource(String input) throws FormatterException {
    return formatSource(input, ImmutableList.of(Range.closedOpen(0, input.length())));
  }

  /**
   * Formats an input string (a Java compilation unit) and fixes imports.
   *
   * <p>Fixing imports includes ordering, spacing, and removal of unused import statements.
   *
   * @param input the input string
   * @return the output string
   * @throws FormatterException if the input string cannot be parsed
   * @see <a
   *     href="https://google.github.io/styleguide/javaguide.html#s3.3.3-import-ordering-and-spacing">
   *     Google Java Style Guide - 3.3.3 Import ordering and spacing</a>
   */
  public String formatSourceAndFixImports(String input) throws FormatterException {
    input = ImportOrderer.reorderImports(input, options.style());
    input = RemoveUnusedImports.removeUnusedImports(input);
    String formatted = formatSource(input);
    formatted = StringWrapper.wrap(formatted, this);
    return formatted;
  }

  /**
   * Format an input string (a Java compilation unit), for only the specified character ranges.
   * These ranges are extended as necessary (e.g., to encompass whole lines).
   *
   * @param input the input string
   * @param characterRanges the character ranges to be reformatted
   * @return the output string
   * @throws FormatterException if the input string cannot be parsed
   */
  public String formatSource(String input, Collection<Range<Integer>> characterRanges)
      throws FormatterException {
    return JavaOutput.applyReplacements(input, getFormatReplacements(input, characterRanges));
  }

  /**
   * Emit a list of {@link Replacement}s to convert from input to output.
   *
   * @param input the input compilation unit
   * @param characterRanges the character ranges to reformat
   * @return a list of {@link Replacement}s, sorted from low index to high index, without overlaps
   * @throws FormatterException if the input string cannot be parsed
   */
  public ImmutableList<Replacement> getFormatReplacements(
      String input, Collection<Range<Integer>> characterRanges) throws FormatterException {
    JavaInput javaInput = new JavaInput(input);

    // TODO(cushon): this is only safe because the modifier ordering doesn't affect whitespace,
    // and doesn't change the replacements that are output. This is not true in general for
    // 'de-linting' changes (e.g. import ordering).
    javaInput = ModifierOrderer.reorderModifiers(javaInput, characterRanges);

    String lineSeparator = Newlines.guessLineSeparator(input);
    JavaOutput javaOutput =
        new JavaOutput(lineSeparator, javaInput, new JavaCommentsHelper(lineSeparator, options));
    try {
      format(javaInput, javaOutput, options);
    } catch (FormattingError e) {
      throw new FormatterException(e.diagnostics());
    }
    RangeSet<Integer> tokenRangeSet = javaInput.characterRangesToTokenRanges(characterRanges);
    return javaOutput.getFormatReplacements(tokenRangeSet);
  }

  /**
   * Converts zero-indexed, [closed, open) line ranges in the given source file to character ranges.
   */
  public static RangeSet<Integer> lineRangesToCharRanges(
      String input, RangeSet<Integer> lineRanges) {
    List<Integer> lines = new ArrayList<>();
    Iterators.addAll(lines, Newlines.lineOffsetIterator(input));
    lines.add(input.length() + 1);

    final RangeSet<Integer> characterRanges = TreeRangeSet.create();
    for (Range<Integer> lineRange :
        lineRanges.subRangeSet(Range.closedOpen(0, lines.size() - 1)).asRanges()) {
      int lineStart = lines.get(lineRange.lowerEndpoint());
      // Exclude the trailing newline. This isn't strictly necessary, but handling blank lines
      // as empty ranges is convenient.
      int lineEnd = lines.get(lineRange.upperEndpoint()) - 1;
      Range<Integer> range = Range.closedOpen(lineStart, lineEnd);
      characterRanges.add(range);
    }
    return characterRanges;
  }
}