Function _splitAndEscapeSelector

src/cdk/testing/component-harness.ts:764–779

* Splits up a compound selector into its parts and escapes any quoted content. The quoted content * has to be escaped, because it can contain commas which will throw throw us off when trying to * split it. * @param selector Selector to be split. * @returns The escaped string where any quoted con

(selector: string)

 * the placeholders.
 */
function _splitAndEscapeSelector(selector: string): [parts: string[], placeholders: string[]] {
  const placeholders: string[] = [];

  // Note that the regex doesn't account for nested quotes so something like `"ab'cd'e"` will be
  // considered as two blocks. It's a bit of an edge case, but if we find that it's a problem,
  // we can make it a bit smarter using a loop. Use this for now since it's more readable and
  // compact. More complete implementation:
  // https://github.com/angular/angular/blob/bd34bc9e89f18a/packages/compiler/src/shadow_css.ts#L655
  const result = selector.replace(/(["'][^["']*["'])/g, (_, keep) => {
    const replaceBy = `__cdkPlaceholder-${placeholders.length}__`;
    placeholders.push(keep);
    return replaceBy;
  });

  return [result.split(',').map(part => part.trim()), placeholders];
}

/** Restores a selector whose content was escaped in `_splitAndEscapeSelector`. */
function _restoreSelector(selector: string, placeholders: string[]): string {