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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs. This binary checks for style issues such as incorrect or missing JSDoc usage, and missing goog.require() statements. It does not do more advanced checks such as typechecking.

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/*
 * Copyright 2008 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp.deps;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMultiset;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multimaps;
import com.google.common.collect.Multiset;
import com.google.javascript.jscomp.CheckLevel;
import com.google.javascript.jscomp.Compiler;
import com.google.javascript.jscomp.CompilerOptions;
import com.google.javascript.jscomp.DiagnosticType;
import com.google.javascript.jscomp.ErrorManager;
import com.google.javascript.jscomp.JSError;
import com.google.javascript.jscomp.JsAst;
import com.google.javascript.jscomp.LazyParsedDependencyInfo;
import com.google.javascript.jscomp.SourceFile;
import com.google.javascript.jscomp.deps.DependencyInfo.Require;
import com.google.javascript.jscomp.deps.ModuleLoader.ModulePath;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.stream.Collectors;

/**
 * Generates deps.js files by scanning JavaScript files for
 * calls to goog.provide(), goog.require() and goog.addDependency().
 *
 * @author [email protected] (Andrew Grieve)
 */
public class DepsGenerator {

  public static enum InclusionStrategy {
    ALWAYS,
    WHEN_IN_SRCS,
    DO_NOT_DUPLICATE
  }

  private static final Logger logger = Logger.getLogger(DepsGenerator.class.getName());

  // See the Flags in MakeJsDeps for descriptions of these.
  private final Collection srcs;
  private final Collection deps;
  private final String closurePathAbs;
  private final InclusionStrategy mergeStrategy;
  private final ModuleLoader loader;
  final ErrorManager errorManager;

  static final DiagnosticType ES6_IMPORT_FOR_NON_ES6_MODULE =
      DiagnosticType.warning(
          "DEPS_ES6_IMPORT_FOR_NON_ES6_MODULE",
          "Cannot import file \"{0}\" because it is not an ES6 module.");

  static final DiagnosticType UNKNOWN_PATH_IMPORT =
      DiagnosticType.warning("DEPS_UNKNOWN_PATH_IMPORT", "Could not find file \"{0}\".");

  static final DiagnosticType SAME_FILE_WARNING = DiagnosticType.warning(
      "DEPS_SAME_FILE",
      "Namespace \"{0}\" is both required and provided in the same file.");

  static final DiagnosticType NEVER_PROVIDED_ERROR =
      DiagnosticType.error(
          "DEPS_NEVER_PROVIDED",
          "Namespace \"{0}\" is required but never provided.\nYou "
              + "need to pass a library that has it in srcs or exports to your target''s deps.");

  static final DiagnosticType DUPE_PROVIDES_WARNING = DiagnosticType.warning(
      "DEPS_DUPE_PROVIDES",
      "Multiple calls to goog.provide(\"{0}\")");

  static final DiagnosticType MULTIPLE_PROVIDES_ERROR = DiagnosticType.error(
      "DEPS_DUPE_PROVIDES",
      "Namespace \"{0}\" is already provided in other file {1}");

  static final DiagnosticType DUPE_REQUIRE_WARNING = DiagnosticType.warning(
      "DEPS_DUPE_REQUIRES",
      "Namespace \"{0}\" is required multiple times");

  static final DiagnosticType NO_DEPS_WARNING = DiagnosticType.warning(
      "DEPS_NO_DEPS",
      "No dependencies found in file");

  /**
   * Creates a new DepsGenerator.
   */
  public DepsGenerator(
      Collection deps,
      Collection srcs,
      InclusionStrategy mergeStrategy,
      String closurePathAbs,
      ErrorManager errorManager,
      ModuleLoader loader) {
    this.deps = deps;
    this.srcs = srcs;
    this.mergeStrategy = mergeStrategy;
    this.closurePathAbs = closurePathAbs;
    this.errorManager = errorManager;
    this.loader = loader;
  }

  /**
   * Performs the parsing inputs and writing of outputs.
   * @throws IOException Occurs upon an IO error.
   * @return Returns a String of goog.addDependency calls that will build
   *     the dependency graph. Returns null if there was an error.
   */
  public String computeDependencyCalls() throws IOException {
    // Build a map of closure-relative path -> DepInfo.
    Map depsFiles = parseDepsFiles();
    if (logger.isLoggable(Level.FINE)) {
      logger.fine("preparsedFiles: " + depsFiles);
    }
    // Find all goog.provides & goog.requires in src files
    Map jsFiles = parseSources(depsFiles.keySet());

    // Check if there were any parse errors.
    if (errorManager.getErrorCount() > 0) {
      return null;
    }

    cleanUpDuplicatedFiles(depsFiles, jsFiles);

    jsFiles = removeMungedSymbols(depsFiles, jsFiles);

    // Check for missing provides or other semantic inconsistencies.
    validateDependencies(depsFiles.values(), jsFiles.values());

    if (errorManager.getErrorCount() > 0) {
      return null;
    }

    ByteArrayOutputStream output = new ByteArrayOutputStream();
    writeDepsContent(depsFiles, jsFiles, new PrintStream(output));
    return new String(output.toByteArray(), UTF_8);
  }

  /**
   * Removes duplicated depsInfo from jsFiles if this info already present in
   * some of the parsed deps.js
   *
   * @param depsFiles DepsInfo from deps.js dependencies
   * @param jsFiles DepsInfo from some of jsSources
   */
  protected void cleanUpDuplicatedFiles(Map depsFiles,
      Map jsFiles) {
    Set depsPathsCopy = new HashSet<>(depsFiles.keySet());
    for (String path : depsPathsCopy) {
      if (mergeStrategy != InclusionStrategy.WHEN_IN_SRCS) {
        jsFiles.remove(path);
      }
    }

    for (String path : jsFiles.keySet()) {
      // If a generated file appears in both the jsFiles and in depsFiles, then
      // remove it from depsFiles in order to get the full path the generated
      // file.
      depsFiles.remove(path);
    }
  }

  /**
   * Removes munged symbols in requires and provides. These munged symbols are from ES6 modules
   * and are generated by {@link ModulePath#toModuleName()}. We do not wish to write these munged
   * symbols to the dependency file.
   *
   * 
    
   *   
  • Makes any require'd munged symbol the require'd file's relative path to Closure.
    • 
   *   
  • Removes munged symbols from the provides list.
    • 
   * 

   */
  private Map removeMungedSymbols(
      Map depFiles, Map jsFiles) {
    Map newJsFiles = new LinkedHashMap<>();
    Map providesMap = new LinkedHashMap<>();
    addToProvideMap(depFiles.values(), providesMap, true);
    addToProvideMap(jsFiles.values(), providesMap, false);

    for (DependencyInfo dependencyInfo : jsFiles.values()) {
      ArrayList newRequires = new ArrayList<>();
      for (Require require : dependencyInfo.getRequires()) {
        if (require.getType() == Require.Type.ES6_IMPORT) {
          // Symbols are unique per file and have nothing to do with paths so map lookups are safe
          // here.
          DependencyInfo provider = providesMap.get(require.getSymbol());
          if (provider == null) {
            reportMissingFile(dependencyInfo, require.getRawText());
          } else {
            // If this is an ES6 module then set the symbol to be its relative path to Closure.
            // ES6 modules in a dependency file do not "provide" anything. Requires can match
            // a provided symbol or a relative path to Closure.
            newRequires.add(require.withSymbol(provider.getPathRelativeToClosureBase()));
          }
        } else {
          // Require is by symbol already so no need to change it.
          newRequires.add(require);
        }
      }

      ImmutableList provides = dependencyInfo.getProvides();

      if ("es6".equals(dependencyInfo.getLoadFlags().get("module"))) {
        String mungedProvide = loader.resolve(dependencyInfo.getName()).toModuleName();
        // Filter out the munged symbol.
        // Note that at the moment ES6 modules should not have any other provides! In the future
        // we may have additional mechanisms to add goog symbols. But for not nothing is officially
        // supported.
        ImmutableList.Builder builder = ImmutableList.builder();
        for (String provide : provides) {
          if (!provide.equals(mungedProvide)
              && !provide.equals(dependencyInfo.getPathRelativeToClosureBase())) {
            builder.add(provide);
          }
        }
        provides = builder.build();
      }

      newJsFiles.put(
          dependencyInfo.getPathRelativeToClosureBase(),
          SimpleDependencyInfo.builder(
                  dependencyInfo.getPathRelativeToClosureBase(), dependencyInfo.getName())
              .setProvides(provides)
              .setRequires(newRequires)
              .setLoadFlags(dependencyInfo.getLoadFlags())
              .build());
    }

    return newJsFiles;
  }

  /**
   * Reports if there are any dependency problems with the given dependency
   * information. Reported problems include:
   *     - A namespace being provided more than once
   *     - A namespace being required multiple times from within one file
   *     - A namespace being provided and required in the same file
   *     - A namespace being required that is never provided
   * @param preparsedFileDependencies Dependency information from existing
   *     deps.js files.
   * @param parsedFileDependencies Dependency information from parsed .js files.
   */
  private void validateDependencies(Iterable preparsedFileDependencies,
      Iterable parsedFileDependencies) {
    // Create a map of namespace -> file providing it.
    // Also report any duplicate provides.
    Map providesMap = new LinkedHashMap<>();
    addToProvideMap(preparsedFileDependencies, providesMap, true);
    addToProvideMap(parsedFileDependencies, providesMap, false);
    // For each require in the parsed sources:
    for (DependencyInfo depInfo : parsedFileDependencies) {
      Multiset symbols = ImmutableMultiset.copyOf(depInfo.getRequiredSymbols());
      for (String symbol : symbols.elementSet()) {
        if (symbols.count(symbol) > 1) {
          reportDuplicateRequire(symbol, depInfo);
        }
      }

      for (Require require : depInfo.getRequires()) {
        String namespace = require.getSymbol();
        // Check for missing provides.
        DependencyInfo provider = providesMap.get(namespace);
        if (provider == null) {
          reportUndefinedNamespace(namespace, depInfo);
        } else if (provider == depInfo) {
          reportSameFile(namespace, depInfo);
        } else {
          depInfo.isModule();
          boolean providerIsEs6Module = "es6".equals(provider.getLoadFlags().get("module"));

          switch (require.getType()) {
            case ES6_IMPORT:
              if (!providerIsEs6Module) {
                reportEs6ImportForNonEs6Module(provider, depInfo);
              }
              break;
            case GOOG_REQUIRE_SYMBOL:
            case PARSED_FROM_DEPS:
              break;
            case COMMON_JS:
            case COMPILER_MODULE:
            default:
              throw new IllegalStateException("Unexpected import type: " + require.getType());
          }
        }
      }
    }
  }

  private void reportMissingFile(DependencyInfo depInfo, String path) {
    errorManager.report(
        CheckLevel.ERROR, JSError.make(depInfo.getName(), -1, -1, UNKNOWN_PATH_IMPORT, path));
  }

  private void reportEs6ImportForNonEs6Module(DependencyInfo provider, DependencyInfo depInfo) {
    errorManager.report(
        CheckLevel.ERROR,
        JSError.make(depInfo.getName(), -1, -1, ES6_IMPORT_FOR_NON_ES6_MODULE, provider.getName()));
  }

  private void reportSameFile(String namespace, DependencyInfo depInfo) {
    errorManager.report(CheckLevel.WARNING,
        JSError.make(depInfo.getName(), -1, -1,
            SAME_FILE_WARNING, namespace));
  }

  private void reportUndefinedNamespace(
      String namespace, DependencyInfo depInfo) {
    errorManager.report(CheckLevel.ERROR,
        JSError.make(depInfo.getName(), -1, -1,
            NEVER_PROVIDED_ERROR, namespace));
  }

  private void reportDuplicateProvide(String namespace, DependencyInfo firstDep,
      DependencyInfo secondDep) {
    if (firstDep == secondDep) {
      if (!firstDep.getPathRelativeToClosureBase().equals(namespace)) {
        errorManager.report(
            CheckLevel.WARNING,
            JSError.make(firstDep.getName(), -1, -1, DUPE_PROVIDES_WARNING, namespace));
      }
    } else {
      errorManager.report(CheckLevel.ERROR,
          JSError.make(secondDep.getName(), -1, -1,
              MULTIPLE_PROVIDES_ERROR, namespace, firstDep.getName()));
    }
  }

  private void reportDuplicateRequire(
      String namespace, DependencyInfo depInfo) {
    errorManager.report(CheckLevel.WARNING,
        JSError.make(depInfo.getName(), -1, -1,
            DUPE_REQUIRE_WARNING, namespace));
  }

  private void reportNoDepsInDepsFile(String filePath) {
    errorManager.report(CheckLevel.WARNING,
        JSError.make(filePath, -1, -1, NO_DEPS_WARNING));
  }

  /**
   * Adds the given DependencyInfos to the given providesMap. Also checks for and reports duplicate
   * provides.
   */
  private void addToProvideMap(
      Iterable depInfos,
      Map providesMap,
      boolean isFromDepsFile) {
    for (DependencyInfo depInfo : depInfos) {
      List provides = new ArrayList<>(depInfo.getProvides());

      // Add a munged symbol to the provides map so that lookups by path requires work as intended.
      if (isFromDepsFile) {
        // Don't add the dependency file itself but every file it says exists instead.
        provides.add(
            loader
                .resolve(
                    PathUtil.makeAbsolute(depInfo.getPathRelativeToClosureBase(), closurePathAbs))
                .toModuleName());
      } else {
        // ES6 modules already provide these munged symbols.
        if (!"es6".equals(depInfo.getLoadFlags().get("module"))) {
          provides.add(loader.resolve(depInfo.getName()).toModuleName());
        }
      }

      // Also add the relative closure path as a provide. At some point we'll swap out the munged
      // symbols for these relative paths. So looks ups by either need to work.
      provides.add(depInfo.getPathRelativeToClosureBase());

      for (String provide : provides) {
        DependencyInfo prevValue = providesMap.put(provide, depInfo);
        // Check for duplicate provides.
        if (prevValue != null) {
          reportDuplicateProvide(provide, prevValue, depInfo);
        }
      }
    }
  }

  protected DepsFileParser createDepsFileParser() {
    DepsFileParser depsParser = new DepsFileParser(errorManager);
    depsParser.setShortcutMode(true);
    return depsParser;
  }

  /**
   * Returns whether we should ignore dependency info in the given deps file.
   */
  protected boolean shouldSkipDepsFile(SourceFile file) {
    return false;
  }

  /**
   * Parses all deps.js files in the deps list and creates a map of
   * closure-relative path -> DependencyInfo.
   */
  private Map parseDepsFiles() throws IOException {
    DepsFileParser depsParser = createDepsFileParser();
    Map depsFiles = new LinkedHashMap<>();
    for (SourceFile file : deps) {
      if (!shouldSkipDepsFile(file)) {
        List
            depInfos = depsParser.parseFileReader(
                file.getName(), file.getCodeReader());
        if (depInfos.isEmpty()) {
          reportNoDepsInDepsFile(file.getName());
        } else {
          for (DependencyInfo info : depInfos) {
            depsFiles.put(info.getPathRelativeToClosureBase(), removeRelativePathProvide(info));
          }
        }
      }
    }

    // If a deps file also appears in srcs, our build tools will move it
    // into srcs.  So we need to scan all the src files for addDependency
    // calls as well.
    for (SourceFile src : srcs) {
      if (!shouldSkipDepsFile(src)) {
        List srcInfos =
            depsParser.parseFileReader(src.getName(), src.getCodeReader());
        for (DependencyInfo info : srcInfos) {
          depsFiles.put(info.getPathRelativeToClosureBase(), removeRelativePathProvide(info));
        }
      }
    }

    return depsFiles;
  }

  private DependencyInfo removeRelativePathProvide(DependencyInfo info) {
    // DepsFileParser adds an ES6 module's relative path to closure as a provide so that
    // the resulting depgraph is valid. But we don't want to write this "fake" provide
    // back out, so remove it here.
    return SimpleDependencyInfo.Builder.from(info)
        .setProvides(
            info.getProvides().stream()
                .filter(p -> !p.equals(info.getPathRelativeToClosureBase()))
                .collect(Collectors.toList()))
        .build();
  }

  /**
   * Parses all source files for dependency information.
   * @param preparsedFiles A set of closure-relative paths.
   *     Files in this set are not parsed if they are encountered in srcs.
   * @return Returns a map of closure-relative paths -> DependencyInfo for the
   *     newly parsed files.
   * @throws IOException Occurs upon an IO error.
   */
  private Map parseSources(
      Set preparsedFiles) throws IOException {
    Map parsedFiles = new LinkedHashMap<>();
    JsFileParser jsParser = new JsFileParser(errorManager).setModuleLoader(loader);
    Compiler compiler = new Compiler();
    compiler.init(ImmutableList.of(), ImmutableList.of(), new CompilerOptions());

    for (SourceFile file : srcs) {
      String closureRelativePath =
          PathUtil.makeRelative(
              closurePathAbs, PathUtil.makeAbsolute(file.getName()));
      if (logger.isLoggable(Level.FINE)) {
        logger.fine("Closure-relative path: " + closureRelativePath);
      }
      if (InclusionStrategy.WHEN_IN_SRCS == mergeStrategy ||
          !preparsedFiles.contains(closureRelativePath)) {
        DependencyInfo depInfo =
            jsParser.parseFile(
                file.getName(), closureRelativePath,
                file.getCode());
        depInfo = new LazyParsedDependencyInfo(depInfo, new JsAst(file), compiler);

        // Kick the source out of memory.
        file.clearCachedSource();
        parsedFiles.put(closureRelativePath, depInfo);
      }
    }

    return parsedFiles;
  }

  /**
   * Creates the content to put into the output deps.js file. If mergeDeps is
   * true, then all of the dependency information in the providedDeps will be
   * included in the output.
   * @throws IOException Occurs upon an IO error.
   */
  private void writeDepsContent(Map depsFiles,
      Map jsFiles, PrintStream out)
      throws IOException {
    // Print all dependencies extracted from srcs.
    writeDepInfos(out, jsFiles.values());

    // Print all dependencies extracted from deps.
    if (mergeStrategy == InclusionStrategy.ALWAYS) {
      // This multimap is just for splitting DepsInfo objects by
      // it's definition deps.js file
      Multimap infosIndex =
          Multimaps.index(depsFiles.values(), DependencyInfo::getName);

      for (String depsPath : infosIndex.keySet()) {
        String path = formatPathToDepsFile(depsPath);
        out.println("\n// Included from: " + path);
        writeDepInfos(out, infosIndex.get(depsPath));
      }
    }
  }

  /**
   * Format the deps file path so that it can be included in the output file.
   */
  protected String formatPathToDepsFile(String path) {
    return path;
  }

  /** Writes goog.addDependency() lines for each DependencyInfo in depInfos. */
  private static void writeDepInfos(PrintStream out, Collection depInfos)
      throws IOException {
    // Print dependencies.
    // Lines look like this:
    // goog.addDependency('../../path/to/file.js', ['goog.Delay'],
    //     ['goog.Disposable', 'goog.Timer']);
    for (DependencyInfo depInfo : depInfos) {
      DependencyInfo.Util.writeAddDependency(out, depInfo);
    }
  }

  static List createSourceFilesFromPaths(
      Collection paths) {
    List files = new ArrayList<>();
    for (String path : paths) {
      files.add(SourceFile.fromFile(path));
    }
    return files;
  }

  static List createSourceFilesFromPaths(String... paths) {
    return createSourceFilesFromPaths(Arrays.asList(paths));
  }

  static List createSourceFilesFromZipPaths(
      Collection paths) throws IOException {
    List zipSourceFiles = new ArrayList<>();
    for (String path : paths) {
      zipSourceFiles.addAll(SourceFile.fromZipFile(path, UTF_8));
    }
    return zipSourceFiles;
  }
}




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