feat($injector): Allow specifying a decorator on $injector

Allows the definition of a decorator on `$injector`

Closes: #13103

Author: lgalfaso

src/auto/injector.js

@@ -642,16 +642,19 @@ function createInjector(modulesToLoad, strictDi) {
             throw $injectorMinErr('unpr', "Unknown provider: {0}", path.join(' <- '));
           })),
       instanceCache = {},
-      instanceInjector = (instanceCache.$injector =
+      protoInstanceInjector =
           createInternalInjector(instanceCache, function(serviceName, caller) {
             var provider = providerInjector.get(serviceName + providerSuffix, caller);
-            return instanceInjector.invoke(provider.$get, provider, undefined, serviceName);
-          }));
-
-
-  forEach(loadModules(modulesToLoad), function(fn) { if (fn) instanceInjector.invoke(fn); });
-
+            return instanceInjector.invoke(
+                provider.$get, provider, undefined, serviceName);
+          }),
+      instanceInjector = protoInstanceInjector;
+
+  providerCache['$injector' + providerSuffix] = { $get: valueFn(protoInstanceInjector) };
+  var runBlocks = loadModules(modulesToLoad);
+  instanceInjector = protoInstanceInjector.get('$injector');
   instanceInjector.strictDi = strictDi;
+  forEach(runBlocks, function(fn) { if (fn) instanceInjector.invoke(fn); });
 
   return instanceInjector;
 

test/auto/injectorSpec.js

@@ -688,6 +688,23 @@ describe('injector', function() {
           expect(log.join('; ')).
             toBe('myDecoratedService:input,dependency1; myService:decInput; dec+origReturn');
         });
+
+
+        it('should allow for decorators to $injector', function() {
+          injector = createInjector(['ng', function($provide) {
+            $provide.decorator('$injector', function($delegate) {
+              return extend({}, $delegate, {get: function(val) {
+                if (val === 'key') {
+                  return 'value';
+                }
+                return $delegate.get(val);
+              }});
+            });
+          }]);
+
+          expect(injector.get('key')).toBe('value');
+          expect(injector.get('$http')).not.toBeUndefined();
+        });
       });
     });