css/lib/stringify/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');
var path = require('path');

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

module.exports = mixin;

/**
 * Ensure Windows-style paths are formatted properly
 */

const makeFriendlyPath = function(aPath) {
  return path.sep === "\\" ? aPath.replace(/\\/g, "/").replace(/^[a-z]:\/?/i, "/") : aPath;
}

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

function mixin(compiler) {
  compiler._comment = compiler.comment;
  compiler.map = new SourceMap();
  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 {Object} [pos]
 * @return {String}
 * @api private
 */

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

    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(sourceFile, pos);
  }

  this.updatePosition(str);

  return str;
};

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

exports.addFile = function(file, pos) {
  if (typeof pos.content !== 'string') return;
  if (Object.prototype.hasOwnProperty.call(this.files, file)) return;

  this.files[file] = pos.content;
};

/**
 * Applies any original source maps to the output and embeds the source file
 * contents in the source map.
 */

exports.applySourceMaps = function() {
  Object.keys(this.files).forEach(function(file) {
    var content = this.files[file];
    this.map.setSourceContent(file, content);

    if (this.options.inputSourcemaps !== false) {
      var originalMap = sourceMapResolve.resolveSync(
        content, file, fs.readFileSync);
      if (originalMap) {
        var map = new SourceMapConsumer(originalMap.map);
        var relativeTo = originalMap.sourcesRelativeTo;
        this.map.applySourceMap(map, file, makeFriendlyPath(path.dirname(relativeTo)));
      }
    }
  }, 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);
};