fix($http): don't run transformData on HEAD methods

src/ng/http.js

@@ -755,9 +755,12 @@ function $HttpProvider() {
 
       function transformResponse(response) {
         // make a copy since the response must be cacheable
-        var resp = extend({}, response, {
-          data: transformData(response.data, response.headers, config.transformResponse)
-        });
+        var resp = extend({}, response);
+        if(response.config.method.toLowerCase() === 'head'){
+          resp.data = response.data;
+        } else {
+          resp.data = transformData(response.data, response.headers, config.transformResponse);
+        }
         return (isSuccess(response.status))
           ? resp
           : $q.reject(resp);

test/ng/httpSpec.js

@@ -1074,6 +1074,17 @@ describe('$http', function() {
           });
 
 
+          it('should deserialize json empty string when response header contains application/json',
+              function() {
+            $httpBackend.expect('GET', '/url').respond('""', {'Content-Type': 'application/json'});
+            $http({method: 'GET', url: '/url'}).success(callback);
+            $httpBackend.flush();
+
+            expect(callback).toHaveBeenCalledOnce();
+            expect(callback.mostRecentCall.args[0]).toEqual('');
+          });
+
+
           it('should deserialize json with security prefix', function() {
             $httpBackend.expect('GET', '/url').respond(')]}\',\n[1, "abc", {"foo":"bar"}]');
             $http({method: 'GET', url: '/url'}).success(callback);
@@ -1094,6 +1105,18 @@ describe('$http', function() {
           });
 
 
+          it('should not attempt to deserialize json when HEAD request', function(){
+            //per http spec for Content-Type, HEAD request should return a Content-Type header
+            //set to what the content type would have been if a get was sent
+            $httpBackend.expect('HEAD', '/url').respond('', {'Content-Type': 'application/json'});
+            $http({method: 'HEAD', url: '/url'}).success(callback);
+            $httpBackend.flush();
+
+            expect(callback).toHaveBeenCalledOnce();
+            expect(callback.mostRecentCall.args[0]).toEqual('');
+          });
+
+
           it('should not deserialize tpl beginning with ng expression', function() {
             $httpBackend.expect('GET', '/url').respond('{{some}}');
             $http.get('/url').success(callback);