fix($location): update internal url with browser url if changed outside of Angular

$browser keeps an internal representation of the browser's url, and although $browser.url()
would return the client's real current url, the $location service that was comparing that
url with $location's representation had no way of knowing when the url had been changed outside
of Angular.

This commit makes browser and location a little bit smarter by setting a flag inside of $browser
when it detects that a url changed outside of Angular, allowing $location to parse the new url
and update its own internal representation of the url (and react appropriately).

Fixes angular#6976

Author: jeffbcross

src/ng/browser.js

@@ -29,7 +29,8 @@ function Browser(window, document, $log, $sniffer) {
       history = window.history,
       setTimeout = window.setTimeout,
       clearTimeout = window.clearTimeout,
-      pendingDeferIds = {};
+      pendingDeferIds = {},
+      urlChangedOutsideAngular = false;
 
   self.isMock = false;
 
@@ -146,6 +147,7 @@ function Browser(window, document, $log, $sniffer) {
    * @param {boolean=} replace Should new url replace current history record ?
    */
   self.url = function(url, replace) {
+    var currentHref;
     // Android Browser BFCache causes location, history reference to become stale.
     if (location !== window.location) location = window.location;
     if (history !== window.history) history = window.history;
@@ -175,7 +177,38 @@ function Browser(window, document, $log, $sniffer) {
       // - newLocation is a workaround for an IE7-9 issue with location.replace and location.href
       //   methods not updating location.href synchronously.
       // - the replacement is a workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=407172
-      return newLocation || location.href.replace(/%27/g,"'");
+      if (newLocation) {
+        return newLocation;
+      }
+      if (lastBrowserUrl !== (currentHref = location.href.replace(/%27/g,"'"))) {
+        urlChangedOutsideAngular = true;
+      }
+      return currentHref;
+    }
+  };
+
+  /**
+   * @name $browser#urlChangedOutsideAngular
+   *
+   * @description
+   * GETTER:
+   * Without any argument, this method just returns current value of urlChangedOutsideAngular.
+   *
+   * SETTER:
+   * With at least one argument, this method sets urlChangedOutsideAngular to new value.
+   *
+   * NOTE: this api is intended for use only by the $location service inside of $locationWatch.
+   *
+   * @param {boolean} val New value to set as urlChangedOutsideAngular,
+   *                  typically used to reset value to false.
+   */
+  self.urlChangedOutsideAngular = function(val) {
+    if (isDefined(val)) {
+      urlChangedOutsideAngular = val;
+      return self;
+    }
+    else {
+      return urlChangedOutsideAngular;
     }
   };
 
@@ -184,6 +217,7 @@ function Browser(window, document, $log, $sniffer) {
 
   function fireUrlChange() {
     newLocation = null;
+    urlChangedOutsideAngular = false;
     if (lastBrowserUrl == self.url()) return;
 
     lastBrowserUrl = self.url();

src/ng/location.js

@@ -744,7 +744,21 @@ function $LocationProvider(){
       if (!changeCounter || oldUrl != $location.absUrl()) {
         changeCounter++;
         $rootScope.$evalAsync(function() {
-          if ($rootScope.$broadcast('$locationChangeStart', $location.absUrl(), oldUrl).
+          /**
+           * $browser should detect if url was changed outside of Angular, in which
+           * case $location should automatically update to the new url.
+           *
+           * NOTE: Detecting outside changes to location happens automatically in $browser via
+           *       window events (or polling if events aren't supported), but those methods are
+           *       async. For this reason, $browser.url() will perform a comparison with each call
+           *       to the method as a getter.
+           * NOTE: Method does not exist on mock $browser
+           */
+          if ($browser.urlChangedOutsideAngular && $browser.urlChangedOutsideAngular()) {
+            $location.$$parse(oldUrl);
+            $browser.urlChangedOutsideAngular(false);
+          }
+          else if ($rootScope.$broadcast('$locationChangeStart', $location.absUrl(), oldUrl).
               defaultPrevented) {
             $location.$$parse(oldUrl);
           } else {

test/ng/locationSpec.js

@@ -769,6 +769,29 @@ describe('$location', function() {
     });
 
 
+    it('should update location when location changed outside of Angular', function() {
+      module(function($windowProvider, $locationProvider, $browserProvider) {
+        $locationProvider.html5Mode(true);
+        $browserProvider.$get = function($document, $window, $log, $sniffer) {
+          var b = new Browser($window, $document, $log, $sniffer);
+          b.pollFns = [];
+          return b;
+        };
+      });
+
+      inject(function($rootScope, $browser, $location, $sniffer){
+        if ($sniffer.history) {
+          window.history.replaceState(null, '', '/hello');
+          // Verify that infinite digest reported in #6976 no longer occurs
+          expect(function() {
+            $rootScope.$digest();
+          }).not.toThrow();
+          expect($location.path()).toBe('/hello');
+        }
+      });
+    });
+
+
     it('should rewrite when hashbang url given', function() {
       initService(true, '!', true);
       inject(