stylelint-bundle-worker.js
function computeSourceURL(sourceRoot, sourceURL, sourceMapURL) {
  sourceURL = sourceURL || '';

  if (sourceRoot) {
    // This follows what Chrome does.
    if (sourceRoot[sourceRoot.length - 1] !== '/' && sourceURL[0] !== '/') {
      sourceRoot += '/';
    }
    // The spec says:
    //   Line 4: An optional source root, useful for relocating source
    //   files on a server or removing repeated values in the
    //   “sources” entry.  This value is prepended to the individual
    //   entries in the “source” field.
    sourceURL = sourceRoot + sourceURL;
  }

  // Historically, SourceMapConsumer did not take the sourceMapURL as
  // a parameter.  This mode is still somewhat supported, which is why
  // this code block is conditional.  However, it's preferable to pass
  // the source map URL to SourceMapConsumer, so that this function
  // can implement the source URL resolution algorithm as outlined in
  // the spec.  This block is basically the equivalent of:
  //    new URL(sourceURL, sourceMapURL).toString()
  // ... except it avoids using URL, which wasn't available in the
  // older releases of node still supported by this library.
  //
  // The spec says:
  //   If the sources are not absolute URLs after prepending of the
  //   “sourceRoot”, the sources are resolved relative to the
  //   SourceMap (like resolving script src in a html document).
  if (sourceMapURL) {
    var parsed = urlParse(sourceMapURL);
    if (!parsed) {
      throw new Error("sourceMapURL could not be parsed");
    }
    if (parsed.path) {
      // Strip the last path component, but keep the "/".
      var index = parsed.path.lastIndexOf('/');
      if (index >= 0) {
        parsed.path = parsed.path.substring(0, index + 1);
      }
    }
    sourceURL = join(urlGenerate(parsed), sourceURL);
  }

  return normalize(sourceURL);
}
function computeSourceURL(sourceRoot, sourceURL, sourceMapURL) {
  sourceURL = sourceURL || '';

  if (sourceRoot) {
    // This follows what Chrome does.
    if (sourceRoot[sourceRoot.length - 1] !== '/' && sourceURL[0] !== '/') {
      sourceRoot += '/';
    }
    // The spec says:
    //   Line 4: An optional source root, useful for relocating source
    //   files on a server or removing repeated values in the
    //   “sources” entry.  This value is prepended to the individual
    //   entries in the “source” field.
    sourceURL = sourceRoot + sourceURL;
  }

  // Historically, SourceMapConsumer did not take the sourceMapURL as
  // a parameter.  This mode is still somewhat supported, which is why
  // this code block is conditional.  However, it's preferable to pass
  // the source map URL to SourceMapConsumer, so that this function
  // can implement the source URL resolution algorithm as outlined in
  // the spec.  This block is basically the equivalent of:
  //    new URL(sourceURL, sourceMapURL).toString()
  // ... except it avoids using URL, which wasn't available in the
  // older releases of node still supported by this library.
  //
  // The spec says:
  //   If the sources are not absolute URLs after prepending of the
  //   “sourceRoot”, the sources are resolved relative to the
  //   SourceMap (like resolving script src in a html document).
  if (sourceMapURL) {
    var parsed = urlParse(sourceMapURL);
    if (!parsed) {
      throw new Error("sourceMapURL could not be parsed");
    }
    if (parsed.path) {
      // Strip the last path component, but keep the "/".
      var index = parsed.path.lastIndexOf('/');
      if (index >= 0) {
        parsed.path = parsed.path.substring(0, index + 1);
      }
    }
    sourceURL = join(urlGenerate(parsed), sourceURL);
  }

  return normalize(sourceURL);
}
Compute the URL of a source given the the source root, the source's
URL, and the source map's URL.