Function addAttrInterpolateDirective

test/angular/1.7/angular.js:11115–11181

(node, directives, value, name, isNgAttr)

    }

    function addAttrInterpolateDirective(node, directives, value, name, isNgAttr) {
      var nodeName = nodeName_(node);
      var trustedContext = getTrustedAttrContext(nodeName, name);
      var mustHaveExpression = !isNgAttr;
      var allOrNothing = ALL_OR_NOTHING_ATTRS[name] || isNgAttr;

      var interpolateFn = $interpolate(value, mustHaveExpression, trustedContext, allOrNothing);

      // no interpolation found -> ignore
      if (!interpolateFn) return;

      if (name === 'multiple' && nodeName === 'select') {
        throw $compileMinErr('selmulti',
            'Binding to the \'multiple\' attribute is not supported. Element: {0}',
            startingTag(node));
      }

      if (EVENT_HANDLER_ATTR_REGEXP.test(name)) {
        throw $compileMinErr('nodomevents', 'Interpolations for HTML DOM event attributes are disallowed');
      }

      directives.push({
        priority: 100,
        compile: function() {
            return {
              pre: function attrInterpolatePreLinkFn(scope, element, attr) {
                var $$observers = (attr.$$observers || (attr.$$observers = createMap()));

                // If the attribute has changed since last $interpolate()ed
                var newValue = attr[name];
                if (newValue !== value) {
                  // we need to interpolate again since the attribute value has been updated
                  // (e.g. by another directive's compile function)
                  // ensure unset/empty values make interpolateFn falsy
                  interpolateFn = newValue && $interpolate(newValue, true, trustedContext, allOrNothing);
                  value = newValue;
                }

                // if attribute was updated so that there is no interpolation going on we don't want to
                // register any observers
                if (!interpolateFn) return;

                // initialize attr object so that it's ready in case we need the value for isolate
                // scope initialization, otherwise the value would not be available from isolate
                // directive's linking fn during linking phase
                attr[name] = interpolateFn(scope);

                ($$observers[name] || ($$observers[name] = [])).$$inter = true;
                (attr.$$observers && attr.$$observers[name].$$scope || scope).
                  $watch(interpolateFn, function interpolateFnWatchAction(newValue, oldValue) {
                    //special case for class attribute addition + removal
                    //so that class changes can tap into the animation
                    //hooks provided by the $animate service. Be sure to
                    //skip animations when the first digest occurs (when
                    //both the new and the old values are the same) since
                    //the CSS classes are the non-interpolated values
                    if (name === 'class' && newValue !== oldValue) {
                      attr.$updateClass(newValue, oldValue);