Revert "Loosen assertion so it matches any production error"

Author: acdlite

scripts/fiber/tests-failing.txt

@@ -1,6 +1,9 @@
 src/isomorphic/classic/__tests__/ReactContextValidator-test.js
 * should pass previous context to lifecycles
 
+src/renderers/dom/__tests__/ReactDOMProduction-test.js
+* should throw with an error code in production
+
 src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js
 * should clean up input value tracking
 * should clean up input textarea tracking

scripts/fiber/tests-passing.txt

@@ -523,7 +523,6 @@ src/renderers/dom/__tests__/ReactDOMProduction-test.js
 * should use prod React
 * should handle a simple flow
 * should call lifecycle methods
-* should throw with an error code in production
 * should keep track of namespace across portals in production
 
 src/renderers/dom/fiber/__tests__/ReactDOMFiber-test.js

src/renderers/dom/__tests__/ReactDOMProduction-test.js

@@ -185,7 +185,12 @@ describe('ReactDOMProduction', () => {
 
       var container = document.createElement('div');
       ReactDOM.render(<Component />, container);
-    }).toThrowError('Minified React error #');
+    }).toThrowError(
+      'Minified React error #109; visit ' +
+      'http://facebook.github.io/react/docs/error-decoder.html?invariant=109&args[]=Component' +
+      ' for the full message or use the non-minified dev environment' +
+      ' for full errors and additional helpful warnings.'
+    );
   });
 
   if (ReactDOMFeatureFlags.useFiber) {

src/renderers/shared/fiber/ReactChildFiber.js

@@ -1189,8 +1189,10 @@ function ChildReconciler(shouldClone, shouldTrackSideEffects) {
     if (disableNewFiberFeatures) {
       // The new child is not an element. If it's not null or false,
       // and the return fiber is a composite component, throw an error.
+      let componentNameSuffix = '(...)';
       switch (returnFiber.tag) {
         case ClassComponent: {
+          componentNameSuffix = '.render()';
           if (__DEV__) {
             const instance = returnFiber.stateNode;
             if (instance.render._isMockFunction && typeof newChild === 'undefined') {
@@ -1199,27 +1201,21 @@ function ChildReconciler(shouldClone, shouldTrackSideEffects) {
               break;
             }
           }
-          const Component = returnFiber.type;
-          invariant(
-            newChild === null || newChild === false,
-            '%s.render(): A valid React element (or null) must be returned. ' +
-            'You may have returned undefined, an array or some other ' +
-            'invalid object.',
-            Component.displayName || Component.name || 'Component',
-          );
-          break;
         }
+        // Intentionally fall through to the next case, which handles both
+        // functions and classes
+        // eslint-disable-next-lined no-fallthrough
         case FunctionalComponent: {
           // Composites accept elements, portals, null, or false
           const Component = returnFiber.type;
           invariant(
             newChild === null || newChild === false,
-            '%s(...): A valid React element (or null) must be returned. ' +
-            'You may have returned undefined, an array or some other ' +
-            'invalid object.',
+            '%s%s: A valid React element (or null) must be ' +
+            'returned. You may have returned undefined, an array or some ' +
+            'other invalid object.',
             Component.displayName || Component.name || 'Component',
+            componentNameSuffix
           );
-          break;
         }
       }
     }