fix(input): add support for dynamically loaded ngMessage directives.

* Currently ngMessage directives inside of an input-container, which are loaded / transcluded dynamically, didn't get initialized properly.
  The animation was not working. As well as the auto-hide didn't work properly.

Fixes #7477. Fixes #7596. Fixes #6810. Fixes #7823

Closes #8387

src/components/input/input.js

@@ -717,16 +717,43 @@ function ngMessageDirective($mdUtil) {
     priority: 100
   };
 
-  function compile(element) {
-    var inputContainer = $mdUtil.getClosest(element, "md-input-container");
+  function compile(tElement) {
+    if (!isInsideInputContainer(tElement)) {
+
+      // When the current element is inside of a document fragment, then we need to check for an input-container
+      // in the postLink, because the element will be later added to the DOM and is currently just in a temporary
+      // fragment, which causes the input-container check to fail.
+      if (isInsideFragment()) {
+        return function (scope, element) {
+          if (isInsideInputContainer(element)) {
+            // Inside of the postLink function, a ngMessage directive will be a comment element, because it's
+            // currently hidden. To access the shown element, we need to use the element from the compile function.
+            initMessageElement(tElement);
+          }
+        };
+      }
+    } else {
+      initMessageElement(tElement);
+    }
 
-    // If we are not a child of an input container, don't do anything
-    if (!inputContainer) return;
+    function isInsideFragment() {
+      var nextNode = tElement[0];
+      while (nextNode = nextNode.parentNode) {
+        if (nextNode.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
+          return true;
+        }
+      }
+      return false;
+    }
 
-    // Add our animation class
-    element.toggleClass('md-input-message-animation', true);
+    function isInsideInputContainer(element) {
+      return !!$mdUtil.getClosest(element, "md-input-container");
+    }
 
-    return {};
+    function initMessageElement(element) {
+      // Add our animation class
+      element.toggleClass('md-input-message-animation', true);
+    }
   }
 }
 

src/components/input/input.spec.js

@@ -436,6 +436,59 @@ describe('md-input-container directive', function() {
     expect(el[0].querySelector("[ng-messages]").classList.contains('md-auto-hide')).toBe(false);
   }));
 
+  it('should set the animation class on the ngMessage properly', inject(function() {
+    var element = compile(
+      '<md-input-container>' +
+        '<input ng-model="inputVal">' +
+        '<div ng-messages>' +
+          '<ng-message id="requiredMessage" when="required">Field required</ng-message>' +
+        '</div>' +
+      '</md-input-container>'
+    );
+
+    var ngMessage = element.find('ng-message');
+    expect(ngMessage).toHaveClass('md-input-message-animation');
+  }));
+
+  it('should set the animation class on a transcluded ngMessage', function() {
+    // We can emulate the transclusion, by wrapping the ngMessage inside of a document fragment.
+    // It is not necessary to add a *extra* component / directive for that, since we just
+    // want to the test the DocumentFragment detection.
+    var fragment = document.createDocumentFragment();
+
+    var inputContainer = compile(
+      '<md-input-container>' +
+        '<input ng-model="inputVal">' +
+        '<div ng-messages id="messageInsertion">' +
+        '</div>' +
+      '</md-input-container>'
+    );
+
+    // We build our element, without compiling and linking it.
+    // Because we invoke those steps manually during the tests.
+    var messageElement = angular.element(
+      '<ng-message id="requiredMessage" when="required">Field Required</ng-message>'
+    );
+
+    fragment.appendChild(messageElement[0]);
+
+    // Only compile the element at this time, and link it to its scope later.
+    // Normally the directive will add the animation class upon compile.
+    var linkFn = $compile(messageElement);
+
+    expect(messageElement).not.toHaveClass('md-input-message-animation');
+
+    // Now we emulate the finish of the transclusion.
+    // We move the element from the fragment into the correct input
+    // container.
+    inputContainer[0].appendChild(messageElement[0]);
+
+    // Manually invoke the postLink function of the directive.
+    linkFn($rootScope.$new());
+
+    expect(messageElement).toHaveClass('md-input-message-animation');
+  });
+
   it('should select the input value on focus', inject(function($timeout) {
     var container = setup('md-select-on-focus');
     var input = container.find('input');