Deprecate module pattern (factory) components

packages/react-dom/src/__tests__/ReactComponentLifeCycle-test.js

@@ -977,7 +977,16 @@ describe('ReactComponentLifeCycle', () => {
     };
 
     const div = document.createElement('div');
-    ReactDOM.render(<Parent ref={c => c && log.push('ref')} />, div);
+    expect(() =>
+      ReactDOM.render(<Parent ref={c => c && log.push('ref')} />, div),
+    ).toWarnDev(
+      'Warning: The <Parent /> component appears to be a function component that returns a class instance. ' +
+        'Change Parent to a class that extends React.Component instead. ' +
+        "If you can't use a class try assigning the prototype on the function as a workaround. " +
+        '`Parent.prototype = React.Component.prototype`. ' +
+        "Don't use an arrow function since it cannot be called with `new` by React.",
+      {withoutStack: true},
+    );
     ReactDOM.render(<Parent ref={c => c && log.push('ref')} />, div);
 
     expect(log).toEqual([

packages/react-dom/src/__tests__/ReactCompositeComponent-test.js

@@ -118,7 +118,14 @@ describe('ReactCompositeComponent', () => {
     }
 
     const el = document.createElement('div');
-    ReactDOM.render(<Child test="test" />, el);
+    expect(() => ReactDOM.render(<Child test="test" />, el)).toWarnDev(
+      'Warning: The <Child /> component appears to be a function component that returns a class instance. ' +
+        'Change Child to a class that extends React.Component instead. ' +
+        "If you can't use a class try assigning the prototype on the function as a workaround. " +
+        '`Child.prototype = React.Component.prototype`. ' +
+        "Don't use an arrow function since it cannot be called with `new` by React.",
+      {withoutStack: true},
+    );
 
     expect(el.textContent).toBe('test');
   });

packages/react-dom/src/__tests__/ReactCompositeComponentState-test.js

@@ -474,7 +474,14 @@ describe('ReactCompositeComponent-state', () => {
     }
 
     const el = document.createElement('div');
-    ReactDOM.render(<Child />, el);
+    expect(() => ReactDOM.render(<Child />, el)).toWarnDev(
+      'Warning: The <Child /> component appears to be a function component that returns a class instance. ' +
+        'Change Child to a class that extends React.Component instead. ' +
+        "If you can't use a class try assigning the prototype on the function as a workaround. " +
+        '`Child.prototype = React.Component.prototype`. ' +
+        "Don't use an arrow function since it cannot be called with `new` by React.",
+      {withoutStack: true},
+    );
 
     expect(el.textContent).toBe('count:123');
   });

packages/react-dom/src/__tests__/ReactDOMServerIntegrationElements-test.js

@@ -644,7 +644,7 @@ describe('ReactDOMServerIntegration', () => {
             },
           };
         };
-        checkFooDiv(await render(<FactoryComponent />));
+        checkFooDiv(await render(<FactoryComponent />, 1));
       });
     });
 

packages/react-dom/src/__tests__/ReactErrorBoundaries-test.internal.js

@@ -768,12 +768,23 @@ describe('ReactErrorBoundaries', () => {
     };
 
     const container = document.createElement('div');
-    ReactDOM.render(
-      <ErrorBoundary>
-        <BrokenComponentWillMountWithContext />
-      </ErrorBoundary>,
-      container,
+    expect(() =>
+      ReactDOM.render(
+        <ErrorBoundary>
+          <BrokenComponentWillMountWithContext />
+        </ErrorBoundary>,
+        container,
+      ),
+    ).toWarnDev(
+      'Warning: The <BrokenComponentWillMountWithContext /> component appears to be a function component that ' +
+        'returns a class instance. ' +
+        'Change BrokenComponentWillMountWithContext to a class that extends React.Component instead. ' +
+        "If you can't use a class try assigning the prototype on the function as a workaround. " +
+        '`BrokenComponentWillMountWithContext.prototype = React.Component.prototype`. ' +
+        "Don't use an arrow function since it cannot be called with `new` by React.",
+      {withoutStack: true},
     );
+
     expect(container.firstChild.textContent).toBe('Caught an error: Hello.');
   });
 

packages/react-dom/src/__tests__/ReactLegacyErrorBoundaries-test.internal.js

@@ -742,11 +742,21 @@ describe('ReactLegacyErrorBoundaries', () => {
     };
 
     const container = document.createElement('div');
-    ReactDOM.render(
-      <ErrorBoundary>
-        <BrokenComponentWillMountWithContext />
-      </ErrorBoundary>,
-      container,
+    expect(() =>
+      ReactDOM.render(
+        <ErrorBoundary>
+          <BrokenComponentWillMountWithContext />
+        </ErrorBoundary>,
+        container,
+      ),
+    ).toWarnDev(
+      'Warning: The <BrokenComponentWillMountWithContext /> component appears to be a function component that ' +
+        'returns a class instance. ' +
+        'Change BrokenComponentWillMountWithContext to a class that extends React.Component instead. ' +
+        "If you can't use a class try assigning the prototype on the function as a workaround. " +
+        '`BrokenComponentWillMountWithContext.prototype = React.Component.prototype`. ' +
+        "Don't use an arrow function since it cannot be called with `new` by React.",
+      {withoutStack: true},
     );
     expect(container.firstChild.textContent).toBe('Caught an error: Hello.');
   });

packages/react-dom/src/__tests__/refs-test.js

@@ -166,7 +166,17 @@ describe('factory components', () => {
       };
     }
 
-    const inst = ReactTestUtils.renderIntoDocument(<Comp />);
+    let inst;
+    expect(
+      () => (inst = ReactTestUtils.renderIntoDocument(<Comp />)),
+    ).toWarnDev(
+      'Warning: The <Comp /> component appears to be a function component that returns a class instance. ' +
+        'Change Comp to a class that extends React.Component instead. ' +
+        "If you can't use a class try assigning the prototype on the function as a workaround. " +
+        '`Comp.prototype = React.Component.prototype`. ' +
+        "Don't use an arrow function since it cannot be called with `new` by React.",
+      {withoutStack: true},
+    );
     expect(inst.refs.elemRef.tagName).toBe('DIV');
   });
 });

packages/react-dom/src/server/ReactPartialRenderer.js

@@ -179,6 +179,7 @@ let didWarnDefaultTextareaValue = false;
 let didWarnInvalidOptionChildren = false;
 const didWarnAboutNoopUpdateForComponent = {};
 const didWarnAboutBadClass = {};
+const didWarnAboutModulePatternComponent = {};
 const didWarnAboutDeprecatedWillMount = {};
 const didWarnAboutUndefinedDerivedState = {};
 const didWarnAboutUninitializedState = {};
@@ -525,6 +526,24 @@ function resolve(
         validateRenderResult(child, Component);
         return;
       }
+
+      if (__DEV__) {
+        const componentName = getComponentName(Component) || 'Unknown';
+        if (!didWarnAboutModulePatternComponent[componentName]) {
+          warningWithoutStack(
+            false,
+            'The <%s /> component appears to be a function component that returns a class instance. ' +
+              'Change %s to a class that extends React.Component instead. ' +
+              "If you can't use a class try assigning the prototype on the function as a workaround. " +
+              "`%s.prototype = React.Component.prototype`. Don't use an arrow function since it " +
+              'cannot be called with `new` by React.',
+            componentName,
+            componentName,
+            componentName,
+          );
+          didWarnAboutModulePatternComponent[componentName] = true;
+        }
+      }
     }
 
     inst.props = element.props;

packages/react-reconciler/src/ReactFiberBeginWork.js

@@ -144,13 +144,15 @@ const ReactCurrentOwner = ReactSharedInternals.ReactCurrentOwner;
 let didReceiveUpdate: boolean = false;
 
 let didWarnAboutBadClass;
+let didWarnAboutModulePatternComponent;
 let didWarnAboutContextTypeOnFunctionComponent;
 let didWarnAboutGetDerivedStateOnFunctionComponent;
 let didWarnAboutFunctionRefs;
 export let didWarnAboutReassigningProps;
 
 if (__DEV__) {
   didWarnAboutBadClass = {};
+  didWarnAboutModulePatternComponent = {};
   didWarnAboutContextTypeOnFunctionComponent = {};
   didWarnAboutGetDerivedStateOnFunctionComponent = {};
   didWarnAboutFunctionRefs = {};
@@ -1222,6 +1224,24 @@ function mountIndeterminateComponent(
     typeof value.render === 'function' &&
     value.$$typeof === undefined
   ) {
+    if (__DEV__) {
+      const componentName = getComponentName(Component) || 'Unknown';
+      if (!didWarnAboutModulePatternComponent[componentName]) {
+        warningWithoutStack(
+          false,
+          'The <%s /> component appears to be a function component that returns a class instance. ' +
+            'Change %s to a class that extends React.Component instead. ' +
+            "If you can't use a class try assigning the prototype on the function as a workaround. " +
+            "`%s.prototype = React.Component.prototype`. Don't use an arrow function since it " +
+            'cannot be called with `new` by React.',
+          componentName,
+          componentName,
+          componentName,
+        );
+        didWarnAboutModulePatternComponent[componentName] = true;
+      }
+    }
+
     // Proceed under the assumption that this is a class instance
     workInProgress.tag = ClassComponent;
 

packages/react-reconciler/src/__tests__/ReactHooks-test.internal.js

@@ -1327,7 +1327,14 @@ describe('ReactHooks', () => {
     expect(renderCount).toBe(1);
 
     renderCount = 0;
-    renderer.update(<Factory />);
+    expect(() => renderer.update(<Factory />)).toWarnDev(
+      'Warning: The <Factory /> component appears to be a function component that returns a class instance. ' +
+        'Change Factory to a class that extends React.Component instead. ' +
+        "If you can't use a class try assigning the prototype on the function as a workaround. " +
+        '`Factory.prototype = React.Component.prototype`. ' +
+        "Don't use an arrow function since it cannot be called with `new` by React.",
+      {withoutStack: true},
+    );
     expect(renderCount).toBe(1);
     renderCount = 0;
     renderer.update(<Factory />);

packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.internal.js

@@ -137,13 +137,22 @@ describe('ReactHooksWithNoopRenderer', () => {
       };
     }
     ReactNoop.render(<Counter />);
-    expect(Scheduler).toFlushAndThrow(
-      'Invalid hook call. Hooks can only be called inside of the body of a function component. This could happen for' +
-        ' one of the following reasons:\n' +
-        '1. You might have mismatching versions of React and the renderer (such as React DOM)\n' +
-        '2. You might be breaking the Rules of Hooks\n' +
-        '3. You might have more than one copy of React in the same app\n' +
-        'See https://fb.me/react-invalid-hook-call for tips about how to debug and fix this problem.',
+    expect(() =>
+      expect(Scheduler).toFlushAndThrow(
+        'Invalid hook call. Hooks can only be called inside of the body of a function component. This could happen ' +
+          'for one of the following reasons:\n' +
+          '1. You might have mismatching versions of React and the renderer (such as React DOM)\n' +
+          '2. You might be breaking the Rules of Hooks\n' +
+          '3. You might have more than one copy of React in the same app\n' +
+          'See https://fb.me/react-invalid-hook-call for tips about how to debug and fix this problem.',
+      ),
+    ).toWarnDev(
+      'Warning: The <Counter /> component appears to be a function component that returns a class instance. ' +
+        'Change Counter to a class that extends React.Component instead. ' +
+        "If you can't use a class try assigning the prototype on the function as a workaround. " +
+        '`Counter.prototype = React.Component.prototype`. ' +
+        "Don't use an arrow function since it cannot be called with `new` by React.",
+      {withoutStack: true},
     );
 
     // Confirm that a subsequent hook works properly.

packages/react-reconciler/src/__tests__/ReactIncremental-test.internal.js

@@ -2026,8 +2026,15 @@ describe('ReactIncremental', () => {
 
     ReactNoop.render(<Recurse />);
     expect(() => expect(Scheduler).toFlushWithoutYielding()).toWarnDev(
-      'Legacy context API has been detected within a strict-mode tree: \n\n' +
-        'Please update the following components: Recurse',
+      [
+        'Warning: The <Recurse /> component appears to be a function component that returns a class instance. ' +
+          'Change Recurse to a class that extends React.Component instead. ' +
+          "If you can't use a class try assigning the prototype on the function as a workaround. " +
+          '`Recurse.prototype = React.Component.prototype`. ' +
+          "Don't use an arrow function since it cannot be called with `new` by React.",
+        'Legacy context API has been detected within a strict-mode tree: \n\n' +
+          'Please update the following components: Recurse',
+      ],
       {withoutStack: true},
     );
     expect(ops).toEqual([

packages/react-reconciler/src/__tests__/ReactIncrementalErrorHandling-test.internal.js

@@ -1596,8 +1596,15 @@ describe('ReactIncrementalErrorHandling', () => {
     expect(() => {
       expect(Scheduler).toFlushAndThrow('Oops!');
     }).toWarnDev(
-      'Legacy context API has been detected within a strict-mode tree: \n\n' +
-        'Please update the following components: Provider',
+      [
+        'Warning: The <Provider /> component appears to be a function component that returns a class instance. ' +
+          'Change Provider to a class that extends React.Component instead. ' +
+          "If you can't use a class try assigning the prototype on the function as a workaround. " +
+          '`Provider.prototype = React.Component.prototype`. ' +
+          "Don't use an arrow function since it cannot be called with `new` by React.",
+        'Legacy context API has been detected within a strict-mode tree: \n\n' +
+          'Please update the following components: Provider',
+      ],
       {withoutStack: true},
     );
   });

packages/react/src/__tests__/ReactStrictMode-test.internal.js

@@ -835,7 +835,6 @@ describe('ReactStrictMode', () => {
             <div>
               <LegacyContextConsumer />
               <FunctionalLegacyContextConsumer />
-              <FactoryLegacyContextConsumer />
             </div>
           );
         }
@@ -845,14 +844,6 @@ describe('ReactStrictMode', () => {
         return null;
       }
 
-      function FactoryLegacyContextConsumer() {
-        return {
-          render() {
-            return null;
-          },
-        };
-      }
-
       LegacyContextProvider.childContextTypes = {
         color: PropTypes.string,
       };
@@ -885,10 +876,6 @@ describe('ReactStrictMode', () => {
         color: PropTypes.string,
       };
 
-      FactoryLegacyContextConsumer.contextTypes = {
-        color: PropTypes.string,
-      };
-
       let rendered;
 
       expect(() => {
@@ -898,7 +885,7 @@ describe('ReactStrictMode', () => {
           '\n    in StrictMode (at **)' +
           '\n    in div (at **)' +
           '\n    in Root (at **)' +
-          '\n\nPlease update the following components: FactoryLegacyContextConsumer, ' +
+          '\n\nPlease update the following components: ' +
           'FunctionalLegacyContextConsumer, LegacyContextConsumer, LegacyContextProvider' +
           '\n\nLearn more about this warning here:' +
           '\nhttps://fb.me/react-strict-mode-warnings',