fix($http): throw more informative error on invalid JSON response

Fixes #15695

Closes #15724

docs/content/error/$http/baddata.ngdoc

@@ -0,0 +1,14 @@
+@ngdoc error
+@name $http:baddata
+@fullName Bad JSON Data
+@description
+
+The default @{link ng.$http#default-transformations `transformResponse`} will try to parse the
+response as JSON if the `Content-Type` header is `application/json` or the response looks like a
+valid JSON-stringified object or array.
+This error occurs when that data is not a valid JSON object.
+
+The error message should provide additional context such as the actual response.
+
+To resolve this error, make sure you pass valid JSON data to `transformResponse` or use an
+appropriate `Content-Type` header for non-JSON data.

src/ng/http.js

@@ -138,7 +138,12 @@ function defaultHttpResponseTransform(data, headers) {
     if (tempData) {
       var contentType = headers('Content-Type');
       if ((contentType && (contentType.indexOf(APPLICATION_JSON) === 0)) || isJsonLike(tempData)) {
-        data = fromJson(tempData);
+        try {
+          data = fromJson(tempData);
+        } catch (e) {
+          throw $httpMinErr('baddata', 'Data must be a valid JSON object. Received: "{0}". ' +
+          'Parse error: "{1}"', data, e);
+        }
       }
     }
   }

test/ng/httpSpec.js

@@ -1369,17 +1369,15 @@ describe('$http', function() {
             }
           );
 
-          it('should forward json deserialization errors to the http error handler',
-              function() {
+          it('should return JSON data with error message if JSON is invalid', function() {
             var errCallback = jasmine.createSpy('error');
-
-            $httpBackend.expect('GET', '/url').respond('abcd', {'Content-Type': 'application/json'});
-            $http({method: 'GET', url: '/url'}).then(callback).catch(errCallback);
+            $httpBackend.expect('GET', '/url').respond('{abcd}', {'Content-Type': 'application/json'});
+            $http.get('/url').then(callback).catch(errCallback);
             $httpBackend.flush();
 
             expect(callback).not.toHaveBeenCalled();
             expect(errCallback).toHaveBeenCalledOnce();
-            expect(errCallback.calls.mostRecent().args[0]).toEqual(jasmine.any(SyntaxError));
+            expect(errCallback.calls.mostRecent().args[0]).toEqualMinErr('$http', 'baddata');
           });
 
         });