basic-source-map-consumer.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 util = require('./util');
  var binarySearch = require('./binary-search');
  var ArraySet = require('./array-set').ArraySet;
  var base64VLQ = require('./base64-vlq');
  var SourceMapConsumer = require('./source-map-consumer').SourceMapConsumer;

  /**
   * A BasicSourceMapConsumer instance represents a parsed source map which we can
   * query for information about the original file positions by giving it a file
   * position in the generated source.
   *
   * The only parameter is the raw source map (either as a JSON string, or
   * already parsed to an object). According to the spec, source maps have the
   * following attributes:
   *
   *   - version: Which version of the source map spec this map is following.
   *   - sources: An array of URLs to the original source files.
   *   - names: An array of identifiers which can be referrenced by individual mappings.
   *   - sourceRoot: Optional. The URL root from which all sources are relative.
   *   - sourcesContent: Optional. An array of contents of the original source files.
   *   - mappings: A string of base64 VLQs which contain the actual mappings.
   *   - file: Optional. The generated file this source map is associated with.
   *
   * Here is an example source map, taken from the source map spec[0]:
   *
   *     {
   *       version : 3,
   *       file: "out.js",
   *       sourceRoot : "",
   *       sources: ["foo.js", "bar.js"],
   *       names: ["src", "maps", "are", "fun"],
   *       mappings: "AA,AB;;ABCDE;"
   *     }
   *
   * [0]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit?pli=1#
   */
  function BasicSourceMapConsumer(aSourceMap) {
    var sourceMap = aSourceMap;
    if (typeof aSourceMap === 'string') {
      sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
    }

    var version = util.getArg(sourceMap, 'version');
    var sources = util.getArg(sourceMap, 'sources');
    // Sass 3.3 leaves out the 'names' array, so we deviate from the spec (which
    // requires the array) to play nice here.
    var names = util.getArg(sourceMap, 'names', []);
    var sourceRoot = util.getArg(sourceMap, 'sourceRoot', null);
    var sourcesContent = util.getArg(sourceMap, 'sourcesContent', null);
    var mappings = util.getArg(sourceMap, 'mappings');
    var file = util.getArg(sourceMap, 'file', null);

    // Once again, Sass deviates from the spec and supplies the version as a
    // string rather than a number, so we use loose equality checking here.
    if (version != this._version) {
      throw new Error('Unsupported version: ' + version);
    }

    // Some source maps produce relative source paths like "./foo.js" instead of
    // "foo.js".  Normalize these first so that future comparisons will succeed.
    // See bugzil.la/1090768.
    sources = sources.map(util.normalize);

    // Pass `true` below to allow duplicate names and sources. While source maps
    // are intended to be compressed and deduplicated, the TypeScript compiler
    // sometimes generates source maps with duplicates in them. See Github issue
    // #72 and bugzil.la/889492.
    this._names = ArraySet.fromArray(names, true);
    this._sources = ArraySet.fromArray(sources, true);

    this.sourceRoot = sourceRoot;
    this.sourcesContent = sourcesContent;
    this._mappings = mappings;
    this.file = file;
  }

  BasicSourceMapConsumer.prototype = Object.create(SourceMapConsumer.prototype);
  BasicSourceMapConsumer.prototype.consumer = SourceMapConsumer;

  /**
   * Create a BasicSourceMapConsumer from a SourceMapGenerator.
   *
   * @param SourceMapGenerator aSourceMap
   *        The source map that will be consumed.
   * @returns BasicSourceMapConsumer
   */
  BasicSourceMapConsumer.fromSourceMap =
    function SourceMapConsumer_fromSourceMap(aSourceMap) {
      var smc = Object.create(BasicSourceMapConsumer.prototype);

      smc._names = ArraySet.fromArray(aSourceMap._names.toArray(), true);
      smc._sources = ArraySet.fromArray(aSourceMap._sources.toArray(), true);
      smc.sourceRoot = aSourceMap._sourceRoot;
      smc.sourcesContent = aSourceMap._generateSourcesContent(smc._sources.toArray(),
                                                              smc.sourceRoot);
      smc.file = aSourceMap._file;

      smc.__generatedMappings = aSourceMap._mappings.toArray().slice();
      smc.__originalMappings = aSourceMap._mappings.toArray().slice()
        .sort(util.compareByOriginalPositions);

      return smc;
    };

  /**
   * The version of the source mapping spec that we are consuming.
   */
  BasicSourceMapConsumer.prototype._version = 3;

  /**
   * The list of original sources.
   */
  Object.defineProperty(BasicSourceMapConsumer.prototype, 'sources', {
    get: function () {
      return this._sources.toArray().map(function (s) {
        return this.sourceRoot != null ? util.join(this.sourceRoot, s) : s;
      }, this);
    }
  });

  /**
   * Parse the mappings in a string in to a data structure which we can easily
   * query (the ordered arrays in the `this.__generatedMappings` and
   * `this.__originalMappings` properties).
   */
  BasicSourceMapConsumer.prototype._parseMappings =
    function SourceMapConsumer_parseMappings(aStr, aSourceRoot) {
      var generatedLine = 1;
      var previousGeneratedColumn = 0;
      var previousOriginalLine = 0;
      var previousOriginalColumn = 0;
      var previousSource = 0;
      var previousName = 0;
      var str = aStr;
      var temp = {};
      var mapping;

      while (str.length > 0) {
        if (str.charAt(0) === ';') {
          generatedLine++;
          str = str.slice(1);
          previousGeneratedColumn = 0;
        }
        else if (str.charAt(0) === ',') {
          str = str.slice(1);
        }
        else {
          mapping = {};
          mapping.generatedLine = generatedLine;

          // Generated column.
          base64VLQ.decode(str, temp);
          mapping.generatedColumn = previousGeneratedColumn + temp.value;
          previousGeneratedColumn = mapping.generatedColumn;
          str = temp.rest;

          if (str.length > 0 && !this._nextCharIsMappingSeparator(str)) {
            // Original source.
            base64VLQ.decode(str, temp);
            mapping.source = this._sources.at(previousSource + temp.value);
            previousSource += temp.value;
            str = temp.rest;
            if (str.length === 0 || this._nextCharIsMappingSeparator(str)) {
              throw new Error('Found a source, but no line and column');
            }

            // Original line.
            base64VLQ.decode(str, temp);
            mapping.originalLine = previousOriginalLine + temp.value;
            previousOriginalLine = mapping.originalLine;
            // Lines are stored 0-based
            mapping.originalLine += 1;
            str = temp.rest;
            if (str.length === 0 || this._nextCharIsMappingSeparator(str)) {
              throw new Error('Found a source and line, but no column');
            }

            // Original column.
            base64VLQ.decode(str, temp);
            mapping.originalColumn = previousOriginalColumn + temp.value;
            previousOriginalColumn = mapping.originalColumn;
            str = temp.rest;

            if (str.length > 0 && !this._nextCharIsMappingSeparator(str)) {
              // Original name.
              base64VLQ.decode(str, temp);
              mapping.name = this._names.at(previousName + temp.value);
              previousName += temp.value;
              str = temp.rest;
            }
          }

          this.__generatedMappings.push(mapping);
          if (typeof mapping.originalLine === 'number') {
            this.__originalMappings.push(mapping);
          }
        }
      }

      this.__generatedMappings.sort(util.compareByGeneratedPositions);
      this.__originalMappings.sort(util.compareByOriginalPositions);
    };

  /**
   * Find the mapping that best matches the hypothetical "needle" mapping that
   * we are searching for in the given "haystack" of mappings.
   */
  BasicSourceMapConsumer.prototype._findMapping =
    function SourceMapConsumer_findMapping(aNeedle, aMappings, aLineName,
                                           aColumnName, aComparator) {
      // To return the position we are searching for, we must first find the
      // mapping for the given position and then return the opposite position it
      // points to. Because the mappings are sorted, we can use binary search to
      // find the best mapping.

      if (aNeedle[aLineName] <= 0) {
        throw new TypeError('Line must be greater than or equal to 1, got '
                            + aNeedle[aLineName]);
      }
      if (aNeedle[aColumnName] < 0) {
        throw new TypeError('Column must be greater than or equal to 0, got '
                            + aNeedle[aColumnName]);
      }

      return binarySearch.search(aNeedle, aMappings, aComparator);
    };

  /**
   * Compute the last column for each generated mapping. The last column is
   * inclusive.
   */
  BasicSourceMapConsumer.prototype.computeColumnSpans =
    function SourceMapConsumer_computeColumnSpans() {
      for (var index = 0; index < this._generatedMappings.length; ++index) {
        var mapping = this._generatedMappings[index];

        // Mappings do not contain a field for the last generated columnt. We
        // can come up with an optimistic estimate, however, by assuming that
        // mappings are contiguous (i.e. given two consecutive mappings, the
        // first mapping ends where the second one starts).
        if (index + 1 < this._generatedMappings.length) {
          var nextMapping = this._generatedMappings[index + 1];

          if (mapping.generatedLine === nextMapping.generatedLine) {
            mapping.lastGeneratedColumn = nextMapping.generatedColumn - 1;
            continue;
          }
        }

        // The last mapping for each line spans the entire line.
        mapping.lastGeneratedColumn = Infinity;
      }
    };

  /**
   * Returns the original source, line, and column information for the generated
   * source's line and column positions provided. The only argument is an object
   * with the following properties:
   *
   *   - line: The line number in the generated source.
   *   - column: The column number in the generated source.
   *
   * and an object is returned with the following properties:
   *
   *   - source: The original source file, or null.
   *   - line: The line number in the original source, or null.
   *   - column: The column number in the original source, or null.
   *   - name: The original identifier, or null.
   */
  BasicSourceMapConsumer.prototype.originalPositionFor =
    function SourceMapConsumer_originalPositionFor(aArgs) {
      var needle = {
        generatedLine: util.getArg(aArgs, 'line'),
        generatedColumn: util.getArg(aArgs, 'column')
      };

      var index = this._findMapping(needle,
                                    this._generatedMappings,
                                    "generatedLine",
                                    "generatedColumn",
                                    util.compareByGeneratedPositions);

      if (index >= 0) {
        var mapping = this._generatedMappings[index];

        if (mapping.generatedLine === needle.generatedLine) {
          var source = util.getArg(mapping, 'source', null);
          if (source != null && this.sourceRoot != null) {
            source = util.join(this.sourceRoot, source);
          }
          return {
            source: source,
            line: util.getArg(mapping, 'originalLine', null),
            column: util.getArg(mapping, 'originalColumn', null),
            name: util.getArg(mapping, 'name', null)
          };
        }
      }

      return {
        source: null,
        line: null,
        column: null,
        name: null
      };
    };

  /**
   * Returns the original source content. The only argument is the url of the
   * original source file. Returns null if no original source content is
   * availible.
   */
  BasicSourceMapConsumer.prototype.sourceContentFor =
    function SourceMapConsumer_sourceContentFor(aSource, nullOnMissing) {
      if (!this.sourcesContent) {
        return null;
      }

      if (this.sourceRoot != null) {
        aSource = util.relative(this.sourceRoot, aSource);
      }

      if (this._sources.has(aSource)) {
        return this.sourcesContent[this._sources.indexOf(aSource)];
      }

      var url;
      if (this.sourceRoot != null
          && (url = util.urlParse(this.sourceRoot))) {
        // XXX: file:// URIs and absolute paths lead to unexpected behavior for
        // many users. We can help them out when they expect file:// URIs to
        // behave like it would if they were running a local HTTP server. See
        // https://bugzilla.mozilla.org/show_bug.cgi?id=885597.
        var fileUriAbsPath = aSource.replace(/^file:\/\//, "");
        if (url.scheme == "file"
            && this._sources.has(fileUriAbsPath)) {
          return this.sourcesContent[this._sources.indexOf(fileUriAbsPath)]
        }

        if ((!url.path || url.path == "/")
            && this._sources.has("/" + aSource)) {
          return this.sourcesContent[this._sources.indexOf("/" + aSource)];
        }
      }

      // This function is used recursively from
      // IndexedSourceMapConsumer.prototype.sourceContentFor. In that case, we
      // don't want to throw if we can't find the source - we just want to
      // return null, so we provide a flag to exit gracefully.
      if (nullOnMissing) {
        return null;
      }
      else {
        throw new Error('"' + aSource + '" is not in the SourceMap.');
      }
    };

  /**
   * Returns the generated line and column information for the original source,
   * line, and column positions provided. The only argument is an object with
   * the following properties:
   *
   *   - source: The filename of the original source.
   *   - line: The line number in the original source.
   *   - column: The column number in the original source.
   *
   * and an object is returned with the following properties:
   *
   *   - line: The line number in the generated source, or null.
   *   - column: The column number in the generated source, or null.
   */
  BasicSourceMapConsumer.prototype.generatedPositionFor =
    function SourceMapConsumer_generatedPositionFor(aArgs) {
      var needle = {
        source: util.getArg(aArgs, 'source'),
        originalLine: util.getArg(aArgs, 'line'),
        originalColumn: util.getArg(aArgs, 'column')
      };

      if (this.sourceRoot != null) {
        needle.source = util.relative(this.sourceRoot, needle.source);
      }

      var index = this._findMapping(needle,
                                    this._originalMappings,
                                    "originalLine",
                                    "originalColumn",
                                    util.compareByOriginalPositions);

      if (index >= 0) {
        var mapping = this._originalMappings[index];

        return {
          line: util.getArg(mapping, 'generatedLine', null),
          column: util.getArg(mapping, 'generatedColumn', null),
          lastColumn: util.getArg(mapping, 'lastGeneratedColumn', null)
        };
      }

      return {
        line: null,
        column: null,
        lastColumn: null
      };
    };

  exports.BasicSourceMapConsumer = BasicSourceMapConsumer;

});