angular-cn/aio/tools/transforms/angular-api-package/processors/addMetadataAliases.js

const  CssSelectorParser = require('css-selector-parser').CssSelectorParser;
const cssParser = new CssSelectorParser();
/**
 * @dgProcessor addMetadataAliases
 *
 * Directives and components can also be referenced by their selectors,
 * and Pipes can be referenced by their name.
 * So let's add each selector as an alias to this doc.
 */
module.exports = function addMetadataAliasesProcessor() {
  return {
    $runAfter: ['extractDecoratedClassesProcessor'],
    $runBefore: ['computing-ids'],
    $process: function(docs) {
      docs.forEach(doc => {
        switch(doc.docType) {
        case 'directive':
        case 'component':
          doc.aliases = doc.aliases.concat(extractSelectors(doc[doc.docType + 'Options'].selector));
          break;
        case 'pipe':
          if (doc.pipeOptions.name) {
            doc.aliases = doc.aliases.concat(stripQuotes(doc.pipeOptions.name));
          }
          break;
        }
      });
    }
  };
};

function extractSelectors(selectors) {
  const selectorAST = cssParser.parse(stripQuotes(selectors));
  const rules = selectorAST.selectors ? selectorAST.selectors.map(ruleSet => ruleSet.rule) : [selectorAST.rule];
  return rules.reduce((aliases, rule) => {
    const tagAliases = rule.tagName? [rule.tagName] : [];
    const attrRulesAliases = (rule.attrs || []).map(attr => attr.name);
    return aliases.concat(tagAliases, attrRulesAliases);
  }, []);
}

function stripQuotes(value) {
  return (typeof(value) === 'string') ? value.trim().replace(/^(['"])(.*)\1$/, '$2') : value;
}