fix($http): don't parse templates as JSON

The default behaviour causes issues with a wide variety of custom interpolation
markers. Even if the JSON test regexps were strengthened to closer match the
standard JSON format, it would still limit the possibilities of different custom
interpolation markers.

BREAKING CHANGE: $http calls using either the $templateCache, or with custom
Accept headers not including `application/json` will no longer parse JSON.

Closes angular#5756

Author: caitp

src/ng/http.js

@@ -133,7 +133,8 @@ function $HttpProvider() {
   var responseInterceptorFactories = this.responseInterceptors = [];
 
   this.$get = ['$httpBackend', '$browser', '$cacheFactory', '$rootScope', '$q', '$injector',
-      function($httpBackend, $browser, $cacheFactory, $rootScope, $q, $injector) {
+      '$templateCache',
+      function($httpBackend, $browser, $cacheFactory, $rootScope, $q, $injector, $templateCache) {
 
     var defaultCache = $cacheFactory('$http');
 
@@ -678,8 +679,16 @@ function $HttpProvider() {
         transformRequest: defaults.transformRequest,
         transformResponse: defaults.transformResponse
       };
+
       var headers = mergeHeaders(requestConfig);
 
+      if (requestConfig.cache === $templateCache || (typeof headers['Accept'] === 'string' &&
+          headers['Accept'].indexOf('application/json') < 0)) {
+        config.transformResponse = [function(data) {
+          return data;
+        }];
+      }
+
       extend(config, requestConfig);
       config.headers = headers;
       config.method = uppercase(config.method);

test/ng/httpSpec.js

@@ -1062,6 +1062,24 @@ describe('$http', function() {
             expect(callback).toHaveBeenCalledOnce();
             expect(callback.mostRecentCall.args[0]).toEqual('{{some}}');
           });
+
+          it('should not deserialize tpl beginning with custom interpolation markers', inject(function($templateCache) {
+            $httpBackend.expect('GET', '/url').respond('{[foo.bar.baz]}');
+            $http.get('/url', { cache: $templateCache }).success(callback);
+            $httpBackend.flush();
+
+            expect(callback).toHaveBeenCalledOnce();
+            expect(callback.mostRecentCall.args[0]).toEqual('{[foo.bar.baz]}');
+
+            callback.reset();
+
+            $httpBackend.expect('GET', '/url2').respond('[{foo.bar.baz}]');
+            $http.get('/url2', { headers: { Accept: 'text/plain' } }).success(callback);
+            $httpBackend.flush();
+
+            expect(callback).toHaveBeenCalledOnce();
+            expect(callback.mostRecentCall.args[0]).toEqual('[{foo.bar.baz}]');       
+          }));
         });