fix($location): correctly handle external URL change during $digest

Previously, when the URL was changed directly (e.g. via `location.href`) during
a `$digest` (e.g. via `scope.$evalAsync()` or `promise.then()`) the change was
not handled correctly, unless a `popstate` or `hashchange` event was fired
synchronously.

This wasn't an issue in most browsers, where the `popstate` event was fired
synchronously. In IE11 though, the `popstate` event is not fired at all for
hash-only changes ([known bug][1]) and the `hashchange` event is fired
asynchronously (which is too late).

This commit fixes it by keeping track of `$location` setter methods being called
and only processing a URL change if it originated from such a call. If there is
a URL difference but no setter method has been called, this means that the
browser URL has been updated directly and the change hasn't yet been propagated
to `$location` (e.g. due to no synchronous `popstate` event). In that case, the
change will be propagated later by the (asynchronous) `hashchange` event.

[1]: https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/3740423/

Fixes #15556

Author: gkalpak

src/ng/location.js

@@ -137,6 +137,8 @@ function LocationHtml5Url(appBase, appBaseNoFile, basePrefix) {
 
     this.$$url = encodePath(this.$$path) + (search ? '?' + search : '') + hash;
     this.$$absUrl = appBaseNoFile + this.$$url.substr(1); // first char is always '/'
+
+    this.$$urlUpdatedByLocation = true;
   };
 
   this.$$parseLinkUrl = function(url, relHref) {
@@ -270,6 +272,8 @@ function LocationHashbangUrl(appBase, appBaseNoFile, hashPrefix) {
 
     this.$$url = encodePath(this.$$path) + (search ? '?' + search : '') + hash;
     this.$$absUrl = appBase + (this.$$url ? hashPrefix + this.$$url : '');
+
+    this.$$urlUpdatedByLocation = true;
   };
 
   this.$$parseLinkUrl = function(url, relHref) {
@@ -327,6 +331,8 @@ function LocationHashbangInHtml5Url(appBase, appBaseNoFile, hashPrefix) {
     this.$$url = encodePath(this.$$path) + (search ? '?' + search : '') + hash;
     // include hashPrefix in $$absUrl when $$url is empty so IE9 does not reload page because of removal of '#'
     this.$$absUrl = appBase + hashPrefix + this.$$url;
+
+    this.$$urlUpdatedByLocation = true;
   };
 
 }
@@ -656,6 +662,7 @@ forEach([LocationHashbangInHtml5Url, LocationHashbangUrl, LocationHtml5Url], fun
     // but we're changing the $$state reference to $browser.state() during the $digest
     // so the modification window is narrow.
     this.$$state = isUndefined(state) ? null : state;
+    this.$$urlUpdatedByLocation = true;
 
     return this;
   };
@@ -968,36 +975,40 @@ function $LocationProvider() {
 
     // update browser
     $rootScope.$watch(function $locationWatch() {
-      var oldUrl = trimEmptyHash($browser.url());
-      var newUrl = trimEmptyHash($location.absUrl());
-      var oldState = $browser.state();
-      var currentReplace = $location.$$replace;
-      var urlOrStateChanged = oldUrl !== newUrl ||
-        ($location.$$html5 && $sniffer.history && oldState !== $location.$$state);
-
-      if (initializing || urlOrStateChanged) {
-        initializing = false;
-
-        $rootScope.$evalAsync(function() {
-          var newUrl = $location.absUrl();
-          var defaultPrevented = $rootScope.$broadcast('$locationChangeStart', newUrl, oldUrl,
-              $location.$$state, oldState).defaultPrevented;
-
-          // if the location was changed by a `$locationChangeStart` handler then stop
-          // processing this location change
-          if ($location.absUrl() !== newUrl) return;
-
-          if (defaultPrevented) {
-            $location.$$parse(oldUrl);
-            $location.$$state = oldState;
-          } else {
-            if (urlOrStateChanged) {
-              setBrowserUrlWithFallback(newUrl, currentReplace,
-                                        oldState === $location.$$state ? null : $location.$$state);
+      if (initializing || $location.$$urlUpdatedByLocation) {
+        $location.$$urlUpdatedByLocation = false;
+
+        var oldUrl = trimEmptyHash($browser.url());
+        var newUrl = trimEmptyHash($location.absUrl());
+        var oldState = $browser.state();
+        var currentReplace = $location.$$replace;
+        var urlOrStateChanged = oldUrl !== newUrl ||
+          ($location.$$html5 && $sniffer.history && oldState !== $location.$$state);
+
+        if (initializing || urlOrStateChanged) {
+          initializing = false;
+
+          $rootScope.$evalAsync(function() {
+            var newUrl = $location.absUrl();
+            var defaultPrevented = $rootScope.$broadcast('$locationChangeStart', newUrl, oldUrl,
+                $location.$$state, oldState).defaultPrevented;
+
+            // if the location was changed by a `$locationChangeStart` handler then stop
+            // processing this location change
+            if ($location.absUrl() !== newUrl) return;
+
+            if (defaultPrevented) {
+              $location.$$parse(oldUrl);
+              $location.$$state = oldState;
+            } else {
+              if (urlOrStateChanged) {
+                setBrowserUrlWithFallback(newUrl, currentReplace,
+                                          oldState === $location.$$state ? null : $location.$$state);
+              }
+              afterLocationChange(oldUrl, oldState);
             }
-            afterLocationChange(oldUrl, oldState);
-          }
-        });
+          });
+        }
       }
 
       $location.$$replace = false;

test/ng/locationSpec.js

@@ -710,6 +710,7 @@ describe('$location', function() {
       );
     });
 
+
     it('should not infinitely digest when using a semicolon in initial path', function() {
       initService({html5Mode:true,supportHistory:true});
       mockUpBrowser({initialUrl:'http://localhost:9876/;jsessionid=foo', baseHref:'/'});
@@ -721,6 +722,36 @@ describe('$location', function() {
     });
 
 
+    // Support: IE11
+    describe('when changing the browser URL directly during a `$digest`', function() {
+
+      beforeEach(function() {
+        initService({supportHistory: true});
+        mockUpBrowser({initialUrl: 'http://foo.bar/', baseHref: '/'});
+      });
+
+
+      it('should correctly update `$location` and not digest infinitely', inject(
+        function($browser, $location, $rootScope, $window) {
+          $location.url('baz');
+          $rootScope.$digest();
+
+          $rootScope.$apply(function() {
+            $rootScope.$evalAsync(function() {
+              $window.location.href += '/qux';
+            });
+          });
+
+          jqLite($window).triggerHandler('hashchange');
+
+          expect($browser.url()).toBe('http://foo.bar/#!/baz/qux');
+          expect($location.absUrl()).toBe('http://foo.bar/#!/baz/qux');
+        })
+      );
+
+    });
+
+
     function updatePathOnLocationChangeSuccessTo(newPath) {
       inject(function($rootScope, $location) {
         $rootScope.$on('$locationChangeSuccess', function(event, newUrl, oldUrl) {