source-map-generator.js

/* -*- Mode: js; js-indent-level: 2; -*- */
/*
 * Copyright 2011 Mozilla Foundation and contributors
 * Licensed under the New BSD license. See LICENSE or:
 * http://opensource.org/licenses/BSD-3-Clause
 */
if (typeof define !== 'function') {
    var define = require('amdefine')(module, require);
}
define(function (require, exports, module) {

  var base64VLQ = require('./base64-vlq');
  var util = require('./util');
  var ArraySet = require('./array-set').ArraySet;

  /**
   * An instance of the SourceMapGenerator represents a source map which is
   * being built incrementally. To create a new one, you must pass an object
   * with the following properties:
   *
   *   - file: The filename of the generated source.
   *   - sourceRoot: An optional root for all URLs in this source map.
   */
  function SourceMapGenerator(aArgs) {
    this._file = util.getArg(aArgs, 'file');
    this._sourceRoot = util.getArg(aArgs, 'sourceRoot', null);
    this._sources = new ArraySet();
    this._names = new ArraySet();
    this._mappings = [];
    this._sourcesContents = null;
  }

  SourceMapGenerator.prototype._version = 3;

  /**
   * Creates a new SourceMapGenerator based on a SourceMapConsumer
   *
   * @param aSourceMapConsumer The SourceMap.
   */
  SourceMapGenerator.fromSourceMap =
    function SourceMapGenerator_fromSourceMap(aSourceMapConsumer) {
      var sourceRoot = aSourceMapConsumer.sourceRoot;
      var generator = new SourceMapGenerator({
        file: aSourceMapConsumer.file,
        sourceRoot: sourceRoot
      });
      aSourceMapConsumer.eachMapping(function (mapping) {
        var newMapping = {
          generated: {
            line: mapping.generatedLine,
            column: mapping.generatedColumn
          }
        };

        if (mapping.source) {
          newMapping.source = mapping.source;
          if (sourceRoot) {
            newMapping.source = util.relative(sourceRoot, newMapping.source);
          }

          newMapping.original = {
            line: mapping.originalLine,
            column: mapping.originalColumn
          };

          if (mapping.name) {
            newMapping.name = mapping.name;
          }
        }

        generator.addMapping(newMapping);
      });
      aSourceMapConsumer.sources.forEach(function (sourceFile) {
        var content = aSourceMapConsumer.sourceContentFor(sourceFile);
        if (content) {
          generator.setSourceContent(sourceFile, content);
        }
      });
      return generator;
    };

  /**
   * Add a single mapping from original source line and column to the generated
   * source's line and column for this source map being created. The mapping
   * object should have the following properties:
   *
   *   - generated: An object with the generated line and column positions.
   *   - original: An object with the original line and column positions.
   *   - source: The original source file (relative to the sourceRoot).
   *   - name: An optional original token name for this mapping.
   */
  SourceMapGenerator.prototype.addMapping =
    function SourceMapGenerator_addMapping(aArgs) {
      var generated = util.getArg(aArgs, 'generated');
      var original = util.getArg(aArgs, 'original', null);
      var source = util.getArg(aArgs, 'source', null);
      var name = util.getArg(aArgs, 'name', null);

      this._validateMapping(generated, original, source, name);

      if (source && !this._sources.has(source)) {
        this._sources.add(source);
      }

      if (name && !this._names.has(name)) {
        this._names.add(name);
      }

      this._mappings.push({
        generatedLine: generated.line,
        generatedColumn: generated.column,
        originalLine: original != null && original.line,
        originalColumn: original != null && original.column,
        source: source,
        name: name
      });
    };

  /**
   * Set the source content for a source file.
   */
  SourceMapGenerator.prototype.setSourceContent =
    function SourceMapGenerator_setSourceContent(aSourceFile, aSourceContent) {
      var source = aSourceFile;
      if (this._sourceRoot) {
        source = util.relative(this._sourceRoot, source);
      }

      if (aSourceContent !== null) {
        // Add the source content to the _sourcesContents map.
        // Create a new _sourcesContents map if the property is null.
        if (!this._sourcesContents) {
          this._sourcesContents = {};
        }
        this._sourcesContents[util.toSetString(source)] = aSourceContent;
      } else {
        // Remove the source file from the _sourcesContents map.
        // If the _sourcesContents map is empty, set the property to null.
        delete this._sourcesContents[util.toSetString(source)];
        if (Object.keys(this._sourcesContents).length === 0) {
          this._sourcesContents = null;
        }
      }
    };

  /**
   * Applies the mappings of a sub-source-map for a specific source file to the
   * source map being generated. Each mapping to the supplied source file is
   * rewritten using the supplied source map. Note: The resolution for the
   * resulting mappings is the minimium of this map and the supplied map.
   *
   * @param aSourceMapConsumer The source map to be applied.
   * @param aSourceFile Optional. The filename of the source file.
   *        If omitted, SourceMapConsumer's file property will be used.
   */
  SourceMapGenerator.prototype.applySourceMap =
    function SourceMapGenerator_applySourceMap(aSourceMapConsumer, aSourceFile) {
      // If aSourceFile is omitted, we will use the file property of the SourceMap
      if (!aSourceFile) {
        aSourceFile = aSourceMapConsumer.file;
      }
      var sourceRoot = this._sourceRoot;
      // Make "aSourceFile" relative if an absolute Url is passed.
      if (sourceRoot) {
        aSourceFile = util.relative(sourceRoot, aSourceFile);
      }
      // Applying the SourceMap can add and remove items from the sources and
      // the names array.
      var newSources = new ArraySet();
      var newNames = new ArraySet();

      // Find mappings for the "aSourceFile"
      this._mappings.forEach(function (mapping) {
        if (mapping.source === aSourceFile && mapping.originalLine) {
          // Check if it can be mapped by the source map, then update the mapping.
          var original = aSourceMapConsumer.originalPositionFor({
            line: mapping.originalLine,
            column: mapping.originalColumn
          });
          if (original.source !== null) {
            // Copy mapping
            if (sourceRoot) {
              mapping.source = util.relative(sourceRoot, original.source);
            } else {
              mapping.source = original.source;
            }
            mapping.originalLine = original.line;
            mapping.originalColumn = original.column;
            if (original.name !== null && mapping.name !== null) {
              // Only use the identifier name if it's an identifier
              // in both SourceMaps
              mapping.name = original.name;
            }
          }
        }

        var source = mapping.source;
        if (source && !newSources.has(source)) {
          newSources.add(source);
        }

        var name = mapping.name;
        if (name && !newNames.has(name)) {
          newNames.add(name);
        }

      }, this);
      this._sources = newSources;
      this._names = newNames;

      // Copy sourcesContents of applied map.
      aSourceMapConsumer.sources.forEach(function (sourceFile) {
        var content = aSourceMapConsumer.sourceContentFor(sourceFile);
        if (content) {
          if (sourceRoot) {
            sourceFile = util.relative(sourceRoot, sourceFile);
          }
          this.setSourceContent(sourceFile, content);
        }
      }, this);
    };

  /**
   * A mapping can have one of the three levels of data:
   *
   *   1. Just the generated position.
   *   2. The Generated position, original position, and original source.
   *   3. Generated and original position, original source, as well as a name
   *      token.
   *
   * To maintain consistency, we validate that any new mapping being added falls
   * in to one of these categories.
   */
  SourceMapGenerator.prototype._validateMapping =
    function SourceMapGenerator_validateMapping(aGenerated, aOriginal, aSource,
                                                aName) {
      if (aGenerated && 'line' in aGenerated && 'column' in aGenerated
          && aGenerated.line > 0 && aGenerated.column >= 0
          && !aOriginal && !aSource && !aName) {
        // Case 1.
        return;
      }
      else if (aGenerated && 'line' in aGenerated && 'column' in aGenerated
               && aOriginal && 'line' in aOriginal && 'column' in aOriginal
               && aGenerated.line > 0 && aGenerated.column >= 0
               && aOriginal.line > 0 && aOriginal.column >= 0
               && aSource) {
        // Cases 2 and 3.
        return;
      }
      else {
        throw new Error('Invalid mapping: ' + JSON.stringify({
          generated: aGenerated,
          source: aSource,
          orginal: aOriginal,
          name: aName
        }));
      }
    };

  /**
   * Serialize the accumulated mappings in to the stream of base 64 VLQs
   * specified by the source map format.
   */
  SourceMapGenerator.prototype._serializeMappings =
    function SourceMapGenerator_serializeMappings() {
      var previousGeneratedColumn = 0;
      var previousGeneratedLine = 1;
      var previousOriginalColumn = 0;
      var previousOriginalLine = 0;
      var previousName = 0;
      var previousSource = 0;
      var result = '';
      var mapping;

      // The mappings must be guaranteed to be in sorted order before we start
      // serializing them or else the generated line numbers (which are defined
      // via the ';' separators) will be all messed up. Note: it might be more
      // performant to maintain the sorting as we insert them, rather than as we
      // serialize them, but the big O is the same either way.
      this._mappings.sort(util.compareByGeneratedPositions);

      for (var i = 0, len = this._mappings.length; i < len; i++) {
        mapping = this._mappings[i];

        if (mapping.generatedLine !== previousGeneratedLine) {
          previousGeneratedColumn = 0;
          while (mapping.generatedLine !== previousGeneratedLine) {
            result += ';';
            previousGeneratedLine++;
          }
        }
        else {
          if (i > 0) {
            if (!util.compareByGeneratedPositions(mapping, this._mappings[i - 1])) {
              continue;
            }
            result += ',';
          }
        }

        result += base64VLQ.encode(mapping.generatedColumn
                                   - previousGeneratedColumn);
        previousGeneratedColumn = mapping.generatedColumn;

        if (mapping.source) {
          result += base64VLQ.encode(this._sources.indexOf(mapping.source)
                                     - previousSource);
          previousSource = this._sources.indexOf(mapping.source);

          // lines are stored 0-based in SourceMap spec version 3
          result += base64VLQ.encode(mapping.originalLine - 1
                                     - previousOriginalLine);
          previousOriginalLine = mapping.originalLine - 1;

          result += base64VLQ.encode(mapping.originalColumn
                                     - previousOriginalColumn);
          previousOriginalColumn = mapping.originalColumn;

          if (mapping.name) {
            result += base64VLQ.encode(this._names.indexOf(mapping.name)
                                       - previousName);
            previousName = this._names.indexOf(mapping.name);
          }
        }
      }

      return result;
    };

  SourceMapGenerator.prototype._generateSourcesContent =
    function SourceMapGenerator_generateSourcesContent(aSources, aSourceRoot) {
      return aSources.map(function (source) {
        if (!this._sourcesContents) {
          return null;
        }
        if (aSourceRoot) {
          source = util.relative(aSourceRoot, source);
        }
        var key = util.toSetString(source);
        return Object.prototype.hasOwnProperty.call(this._sourcesContents,
                                                    key)
          ? this._sourcesContents[key]
          : null;
      }, this);
    };

  /**
   * Externalize the source map.
   */
  SourceMapGenerator.prototype.toJSON =
    function SourceMapGenerator_toJSON() {
      var map = {
        version: this._version,
        file: this._file,
        sources: this._sources.toArray(),
        names: this._names.toArray(),
        mappings: this._serializeMappings()
      };
      if (this._sourceRoot) {
        map.sourceRoot = this._sourceRoot;
      }
      if (this._sourcesContents) {
        map.sourcesContent = this._generateSourcesContent(map.sources, map.sourceRoot);
      }

      return map;
    };

  /**
   * Render the source map being generated to a string.
   */
  SourceMapGenerator.prototype.toString =
    function SourceMapGenerator_toString() {
      return JSON.stringify(this);
    };

  exports.SourceMapGenerator = SourceMapGenerator;

});