source-map-support.js

/**
 * Module dependencies.
 */

var SourceMap = require('source-map').SourceMapGenerator;
var SourceMapConsumer = require('source-map').SourceMapConsumer;
var sourceMapResolve = require('source-map-resolve');
var fs = require('fs');

/**
 * Expose `mixin()`.
 */

module.exports = mixin;

/**
 * Mixin source map support into `compiler`.
 *
 * @param {Compiler} compiler
 * @api public
 */

function mixin(compiler) {
  var file = compiler.options.filename || 'generated.css';
  compiler._comment = compiler.comment;
  compiler.map = new SourceMap({ file: file });
  compiler.position = { line: 1, column: 1 };
  compiler.files = {};
  for (var k in exports) compiler[k] = exports[k];
}

/**
 * Update position.
 *
 * @param {String} str
 * @api private
 */

exports.updatePosition = function(str) {
  var lines = str.match(/\n/g);
  if (lines) this.position.line += lines.length;
  var i = str.lastIndexOf('\n');
  this.position.column = ~i ? str.length - i : this.position.column + str.length;
};

/**
 * Emit `str`.
 *
 * @param {String} str
 * @param {Number} [pos]
 * @param {Boolean} [startOnly]
 * @return {String}
 * @api private
 */

exports.emit = function(str, pos, startOnly) {
  var sourceFile = pos && pos.source || 'source.css';

  if (pos && pos.start) {
    this.map.addMapping({
      source: sourceFile,
      generated: {
        line: this.position.line,
        column: Math.max(this.position.column - 1, 0)
      },
      original: {
        line: pos.start.line,
        column: pos.start.column - 1
      }
    });

    this.addFile(pos);
  }

  this.updatePosition(str);

  if (!startOnly && pos && pos.end) {
    this.map.addMapping({
      source: sourceFile,
      generated: {
        line: this.position.line,
        column: Math.max(this.position.column - 1, 0)
      },
      original: {
        line: pos.end.line,
        column: pos.end.column - 1
      }
    });

    this.addFile(pos);
  }

  return str;
};

/**
 * Adds a file to the source map output if it has not already been added
 * @param {Object} pos
 */

exports.addFile = function(pos) {
  var file = pos.source || 'source.css';
  if (Object.prototype.hasOwnProperty.call(this.files, file)) return;
  if (typeof pos.content !== 'string') return;
  this.files[file] = pos.content;
};

/**
 * Applies any original source maps to the output.
 */

exports.applySourceMaps = function() {
  Object.keys(this.files).forEach(function(file) {
    var originalMap = sourceMapResolve.resolveSync(
      this.files[file], file, fs.readFileSync);
    if (originalMap) {
      originalMap = new SourceMapConsumer(originalMap.map);
      this.map.applySourceMap(originalMap, file);
    }
  }, this);
};

/**
 * Process comments, drops sourceMap comments.
 * @param {Object} node
 */

exports.comment = function(node) {
  if (/^# sourceMappingURL=/.test(node.comment))
    return this.emit('', node.position);
  else
    return this._comment(node);
};