fix($browser): prevent infinite digests when clearing the hash of a url

By retaining a trailing `#` character in the URL we ensure that the browser
does not attempt a reload, which in turn allows us to read the correct
`location.href` value.

Closes angular#9635

Author: petebacondarwin

src/ng/browser.js

@@ -187,6 +187,14 @@ function Browser(window, document, $log, $sniffer) {
       } else {
         if (!sameBase) {
           reloadLocation = url;
+        } else {
+          // If we are only changing the hash fragment then ensure that we retain a # character
+          // to prevent the page reloading,
+          // which stops us from reading the correct location.href,
+          // which causes $location watches to trigger an infinite digest.
+          if (url.indexOf('#') === -1) {
+            url += '#';
+          }
         }
         if (replace) {
           location.replace(url);

test/ng/browserSpecs.js

@@ -550,6 +550,17 @@ describe('browser', function() {
       expect(locationReplace).not.toHaveBeenCalled();
     });
 
+    it("should retain the # character when the only change is clearing the hash fragment, to prevent page reload", function() {
+      sniffer.history = true;
+
+      browser.url('http://server/#123');
+      expect(fakeWindow.location.href).toEqual('http://server/#123');
+
+      browser.url('http://server/');
+      expect(fakeWindow.location.href).toEqual('http://server/#');
+
+    });
+
     it('should use location.replace when history.replaceState not available', function() {
       sniffer.history = false;
       browser.url('http://new.org', true);
@@ -561,6 +572,7 @@ describe('browser', function() {
       expect(fakeWindow.location.href).toEqual('http://server/');
     });
 
+
     it('should use location.replace and not use replaceState when the url only changed in the hash fragment to please IE10/11', function() {
       sniffer.history = true;
       browser.url('http://server/#123', true);
@@ -572,6 +584,19 @@ describe('browser', function() {
       expect(fakeWindow.location.href).toEqual('http://server/');
     });
 
+
+    it("should retain the # character when replacing and the only change is clearing the hash fragment, to prevent page reload", function() {
+      sniffer.history = true;
+      browser.url('http://server/#123');
+
+      expect(fakeWindow.location.href).toEqual('http://server/#123');
+
+      browser.url('http://server/', true);
+
+      expect(locationReplace).toHaveBeenCalledWith('http://server/#');
+    });
+
+
     it('should return $browser to allow chaining', function() {
       expect(browser.url('http://any.com')).toBe(browser);
     });