Function compileProps

06.Router/basic/js/vue.js:6010–6094

* Compile props on a root element and return * a props link function. * * @param {Element|DocumentFragment} el * @param {Array} propOptions * @param {Vue} vm * @return {Function} propsLinkFn

(el, propOptions, vm)

   */

  function compileProps(el, propOptions, vm) {
    var props = [];
    var names = Object.keys(propOptions);
    var i = names.length;
    var options, name, attr, value, path, parsed, prop;
    while (i--) {
      name = names[i];
      options = propOptions[name] || empty;

      if ('development' !== 'production' && name === '$data') {
        warn('Do not use $data as prop.', vm);
        continue;
      }

      // props could contain dashes, which will be
      // interpreted as minus calculations by the parser
      // so we need to camelize the path here
      path = camelize(name);
      if (!identRE$1.test(path)) {
        'development' !== 'production' && warn('Invalid prop key: "' + name + '". Prop keys ' + 'must be valid identifiers.', vm);
        continue;
      }

      prop = {
        name: name,
        path: path,
        options: options,
        mode: propBindingModes.ONE_WAY,
        raw: null
      };

      attr = hyphenate(name);
      // first check dynamic version
      if ((value = getBindAttr(el, attr)) === null) {
        if ((value = getBindAttr(el, attr + '.sync')) !== null) {
          prop.mode = propBindingModes.TWO_WAY;
        } else if ((value = getBindAttr(el, attr + '.once')) !== null) {
          prop.mode = propBindingModes.ONE_TIME;
        }
      }
      if (value !== null) {
        // has dynamic binding!
        prop.raw = value;
        parsed = parseDirective(value);
        value = parsed.expression;
        prop.filters = parsed.filters;
        // check binding type
        if (isLiteral(value) && !parsed.filters) {
          // for expressions containing literal numbers and
          // booleans, there's no need to setup a prop binding,
          // so we can optimize them as a one-time set.
          prop.optimizedLiteral = true;
        } else {
          prop.dynamic = true;
          // check non-settable path for two-way bindings
          if ('development' !== 'production' && prop.mode === propBindingModes.TWO_WAY && !settablePathRE.test(value)) {
            prop.mode = propBindingModes.ONE_WAY;
            warn('Cannot bind two-way prop with non-settable ' + 'parent path: ' + value, vm);