feat($location): add ability to opt-out of <base/> tag requirement in html5Mode

This feature allows disabling Angular's requirement of using a <base/> tag
when using location in html5Mode, for applications that do not require
using $location in html5Mode in IE9. To accomplish this, the $locationProvider.html5Mode 
method has been changed to accept a definition object which can optionally set a 
requireBase property to false, removing the requirement of a <base> tag being present
when html5Mode is enabled.

BREAKING CHANGE: The $location.html5Mode API has changed to allow enabling html5Mode by
    passing an object (as well as still supporting passing a boolean). Symmetrically, the
    method now returns an object instead of a boolean value.

    To migrate, follow the code example below:

    Before:

    var mode = $locationProvider.html5Mode();

    After:

    var mode = $locationProvider.html5Mode().enabled;

Fixes #8934

docs/content/error/$location/nobase.ngdoc

@@ -4,7 +4,19 @@
 @description
 
 If you configure {@link ng.$location `$location`} to use
-{@link api/ng.provider.$locationProvider `html5Mode`} (`history.pushState`), you need to specify the base URL for the application with a [`<base href="">`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base) tag.
+{@link api/ng.provider.$locationProvider `html5Mode`} (`history.pushState`), you need to specify the base URL for the application with a [`<base href="">`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base) tag or configure
+`$locationProvider` to not require a base tag by passing a definition object with
+`requireBase:false` to `$locationProvider.html5Mode()`:
+
+```javascript
+$locationProvider.html5Mode({
+  enabled: true,
+  requireBase: false
+});
+```
+
+Note that removing the requirement for a <base> tag will have adverse side effects when resolving
+relative paths with `$location` in IE9.
 
 The base URL is then used to resolve all relative URLs throughout the application regardless of the
 entry point into the app.

docs/content/guide/$location.ngdoc

@@ -91,10 +91,11 @@ To configure the `$location` service, retrieve the
 {@link ng.$locationProvider $locationProvider} and set the parameters as follows:
 
 
-- **html5Mode(mode)**: {boolean}<br />
-  `true` - see HTML5 mode<br />
-  `false` - see Hashbang mode<br />
-  default: `false`
+- **html5Mode(mode)**: {boolean|Object}<br />
+  `true` or `enabled:true` - see HTML5 mode<br />
+  `false` or `enabled:false` - see Hashbang mode<br />
+  `requireBase:true` - see Relative links<br />
+  default: `enabled:false`
 
 - **hashPrefix(prefix)**: {string}<br />
   prefix used for Hashbang URLs (used in Hashbang mode or in legacy browser in Html5 mode)<br />
@@ -328,9 +329,11 @@ reload to the original link.
 
 ### Relative links
 
-Be sure to check all relative links, images, scripts etc. Angular requires you to specify the url base in
-the head of your main html file (`<base href="/my-base">`). With that, relative urls will
-always be resolved to this base url, event if the initial url of the document was different.
+Be sure to check all relative links, images, scripts etc. Angular requires you to specify the url
+base in the head of your main html file (`<base href="/my-base">`) unless `html5Mode.requireBase` is
+set to `false` in the html5Mode definition object passed to `$locationProvider.html5Mode()`. With
+that, relative urls will always be resolved to this base url, event if the initial url of the
+document was different.
 
 There is one exception: Links that only contain a hash fragment (e.g. `<a href="#target">`)
 will only change `$location.hash()` and not modify the url otherwise. This is useful for scrolling

src/ng/location.js

@@ -584,7 +584,10 @@ function locationGetterSetter(property, preprocess) {
  */
 function $LocationProvider(){
   var hashPrefix = '',
-      html5Mode = false;
+      html5Mode = {
+        enabled: false,
+        requireBase: true
+      };
 
   /**
    * @ngdoc method
@@ -606,12 +609,30 @@ function $LocationProvider(){
    * @ngdoc method
    * @name $locationProvider#html5Mode
    * @description
-   * @param {boolean=} mode Use HTML5 strategy if available.
-   * @returns {*} current value if used as getter or itself (chaining) if used as setter
+   * @param {(boolean|Object)=} mode If boolean, sets `html5Mode.enabled` to value.
+   *   If object, sets `enabled` and `requireBase` to respective values.
+   *   - **enabled** – `{boolean}` – Sets `html5Mode.enabled`. If true, will rely on
+   *     `history.pushState` to change urls where supported. Will fall back to hash-prefixed paths
+   *     in browsers that do not support `pushState`.
+   *   - **requireBase** - `{boolean}` - Sets `html5Mode.requireBase` (default: `true`). When
+   *     html5Mode is enabled, specifies whether or not a <base> tag is required to be present. If
+   *     `enabled` and `requireBase` are true, and a base tag is not present, an error will be
+   *     thrown when `$location` is injected. See the
+   *     {@link guide/$location $location guide for more information}
+   *
+   * @returns {Object} html5Mode object if used as getter or itself (chaining) if used as setter
    */
   this.html5Mode = function(mode) {
-    if (isDefined(mode)) {
-      html5Mode = mode;
+    if (isBoolean(mode)) {
+      html5Mode.enabled = mode;
+      return this;
+    } else if (isObject(mode)) {
+      html5Mode.enabled = isBoolean(mode.enabled) ?
+          mode.enabled :
+          html5Mode.enabled;
+      html5Mode.requireBase = isBoolean(mode.requireBase) ?
+          mode.requireBase :
+          html5Mode.requireBase;
       return this;
     } else {
       return html5Mode;
@@ -653,8 +674,8 @@ function $LocationProvider(){
         initialUrl = $browser.url(),
         appBase;
 
-    if (html5Mode) {
-      if (!baseHref) {
+    if (html5Mode.enabled) {
+      if (!baseHref && html5Mode.requireBase) {
         throw $locationMinErr('nobase',
           "$location in HTML5 mode requires a <base> tag to be present!");
       }

test/ng/locationSpec.js

@@ -1639,6 +1639,77 @@ describe('$location', function() {
     return undefined;
   }
 
+
+  describe('html5Mode', function() {
+    it('should set enabled and requireBase when called with object', function() {
+      module(function($locationProvider) {
+        expect($locationProvider.html5Mode()).toEqual({
+          enabled: false,
+          requireBase: true
+        });
+      });
+
+      inject(function(){});
+    });
+
+
+    it('should only overwrite existing properties if values are boolean', function() {
+      module(function($locationProvider) {
+        $locationProvider.html5Mode({
+          enabled: 'duh',
+          requireBase: 'probably'
+        });
+
+        expect($locationProvider.html5Mode()).toEqual({
+          enabled: false,
+          requireBase: true
+        });
+      });
+
+      inject(function(){});
+    });
+
+
+    it('should not set unknown input properties to html5Mode object', function() {
+      module(function($locationProvider) {
+        $locationProvider.html5Mode({
+          someProp: 'foo'
+        });
+
+        expect($locationProvider.html5Mode()).toEqual({
+          enabled: false,
+          requireBase: true
+        });
+      });
+
+      inject(function(){});
+    });
+
+
+    it('should default to enabled:false and requireBase:true', function() {
+      module(function($locationProvider) {
+        expect($locationProvider.html5Mode()).toEqual({
+          enabled: false,
+          requireBase: true
+        });
+      });
+
+      inject(function(){});
+    });
+
+
+    it('should return html5Mode object when called without value', function() {
+      module(function($locationProvider) {
+        expect($locationProvider.html5Mode()).toEqual({
+          enabled: false,
+          requireBase: true
+        });
+      });
+
+      inject(function(){});
+    });
+  });
+
   describe('LocationHtml5Url', function() {
     var location, locationIndex;
 
@@ -1661,6 +1732,39 @@ describe('$location', function() {
       // Note: relies on the previous state!
       expect(parseLinkAndReturn(location, 'someIgnoredAbsoluteHref', '#test')).toEqual('http://server/pre/otherPath#test');
     });
+
+
+    it('should complain if no base tag present', function() {
+      module(function($locationProvider) {
+        $locationProvider.html5Mode(true);
+      });
+
+      inject(function($browser, $injector) {
+        $browser.$$baseHref = undefined;
+        expect(function() {
+          $injector.get('$location');
+        }).toThrowMinErr('$location', 'nobase',
+          "$location in HTML5 mode requires a <base> tag to be present!");
+      });
+    });
+
+
+    it('should not complain if baseOptOut set to true in html5Mode', function() {
+      module(function($locationProvider) {
+        $locationProvider.html5Mode({
+          enabled: true,
+          requireBase: false
+        });
+      });
+
+      inject(function($browser, $injector) {
+        $browser.$$baseHref = undefined;
+        expect(function() {
+          $injector.get('$location');
+        }).not.toThrowMinErr('$location', 'nobase',
+          "$location in HTML5 mode requires a <base> tag to be present!");
+      });
+    });
   });