Warn about legacy context when legacy context is not disabled

For environments that still have legacy contexts available, this adds a warning to make the remaining call sites easier to locate and encourage upgrades.

.

Author: kassens

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

@@ -13,6 +13,7 @@ let PropTypes;
 let React;
 let ReactDOMClient;
 let act;
+let assertConsoleErrorDev;
 
 function FunctionComponent(props) {
   return <div>{props.name}</div>;
@@ -24,7 +25,7 @@ describe('ReactFunctionComponent', () => {
     PropTypes = require('prop-types');
     React = require('react');
     ReactDOMClient = require('react-dom/client');
-    act = require('internal-test-utils').act;
+    ({act, assertConsoleErrorDev} = require('internal-test-utils'));
   });
 
   it('should render stateless component', async () => {
@@ -109,6 +110,10 @@ describe('ReactFunctionComponent', () => {
       root.render(<GrandParent test="test" />);
     });
 
+    assertConsoleErrorDev([
+      'Child uses the legacy contextTypes API which will soon be removed. Use React.createContext() with static contextType instead.',
+    ]);
+
     expect(el.textContent).toBe('test');
 
     await act(() => {
@@ -472,6 +477,9 @@ describe('ReactFunctionComponent', () => {
     await act(() => {
       root.render(<Parent />);
     });
+    assertConsoleErrorDev([
+      'Child uses the legacy contextTypes API which will be removed soon. Use React.createContext() with React.useContext() instead.',
+    ]);
     expect(el.textContent).toBe('en');
   });
 

packages/react-reconciler/src/ReactFiberBeginWork.js

@@ -1130,12 +1130,20 @@ function updateFunctionComponent(
       // in updateFuntionComponent but only on mount
       validateFunctionComponentInDev(workInProgress, workInProgress.type);
 
-      if (disableLegacyContext && Component.contextTypes) {
-        console.error(
-          '%s uses the legacy contextTypes API which was removed in React 19. ' +
-            'Use React.createContext() with React.useContext() instead.',
-          getComponentNameFromType(Component) || 'Unknown',
-        );
+      if (Component.contextTypes) {
+        if (disableLegacyContext) {
+          console.error(
+            '%s uses the legacy contextTypes API which was removed in React 19. ' +
+              'Use React.createContext() with React.useContext() instead.',
+            getComponentNameFromType(Component) || 'Unknown',
+          );
+        } else {
+          console.error(
+            '%s uses the legacy contextTypes API which will be removed soon. ' +
+              'Use React.createContext() with React.useContext() instead.',
+            getComponentNameFromType(Component) || 'Unknown',
+          );
+        }
       }
     }
   }

packages/react-reconciler/src/ReactFiberClassComponent.js

@@ -426,6 +426,22 @@ function checkClassInstance(workInProgress: Fiber, ctor: any, newProps: any) {
           name,
         );
       }
+      if (ctor.childContextTypes && !didWarnAboutChildContextTypes.has(ctor)) {
+        didWarnAboutChildContextTypes.add(ctor);
+        console.error(
+          '%s uses the legacy childContextTypes API which will soon be removed. ' +
+            'Use React.createContext() instead.',
+          name,
+        );
+      }
+      if (ctor.contextTypes && !didWarnAboutContextTypes.has(ctor)) {
+        didWarnAboutContextTypes.add(ctor);
+        console.error(
+          '%s uses the legacy contextTypes API which will soon be removed. ' +
+            'Use React.createContext() with static contextType instead.',
+          name,
+        );
+      }
     }
 
     if (typeof instance.componentShouldUpdate === 'function') {

packages/react-server/src/ReactFizzClassComponent.js

@@ -403,6 +403,22 @@ function checkClassInstance(instance: any, ctor: any, newProps: any) {
           name,
         );
       }
+      if (ctor.childContextTypes && !didWarnAboutChildContextTypes.has(ctor)) {
+        didWarnAboutChildContextTypes.add(ctor);
+        console.error(
+          '%s uses the legacy childContextTypes API which will soon be removed. ' +
+            'Use React.createContext() instead.',
+          name,
+        );
+      }
+      if (ctor.contextTypes && !didWarnAboutContextTypes.has(ctor)) {
+        didWarnAboutContextTypes.add(ctor);
+        console.error(
+          '%s uses the legacy contextTypes API which will soon be removed. ' +
+            'Use React.createContext() with static contextType instead.',
+          name,
+        );
+      }
     }
 
     if (typeof instance.componentShouldUpdate === 'function') {

packages/react/src/__tests__/ReactES6Class-test.js

@@ -13,6 +13,7 @@ let PropTypes;
 let React;
 let ReactDOM;
 let ReactDOMClient;
+let assertConsoleErrorDev;
 
 describe('ReactES6Class', () => {
   let container;
@@ -30,6 +31,7 @@ describe('ReactES6Class', () => {
     React = require('react');
     ReactDOM = require('react-dom');
     ReactDOMClient = require('react-dom/client');
+    ({assertConsoleErrorDev} = require('internal-test-utils'));
     container = document.createElement('div');
     root = ReactDOMClient.createRoot(container);
     attachedListener = null;
@@ -287,6 +289,11 @@ describe('ReactES6Class', () => {
         className: PropTypes.string,
       };
       runTest(<Outer />, 'SPAN', 'foo');
+
+      assertConsoleErrorDev([
+        'Outer uses the legacy childContextTypes API which will soon be removed. Use React.createContext() instead.',
+        'Foo uses the legacy contextTypes API which will soon be removed. Use React.createContext() with static contextType instead.',
+      ]);
     });
   }
 
@@ -579,6 +586,10 @@ describe('ReactES6Class', () => {
       }
       Foo.childContextTypes = {bar: PropTypes.string};
       runTest(<Foo />, 'DIV', 'bar-through-context');
+      assertConsoleErrorDev([
+        'Foo uses the legacy childContextTypes API which will soon be removed. Use React.createContext() instead.',
+        'Bar uses the legacy contextTypes API which will soon be removed. Use React.createContext() with static contextType instead.',
+      ]);
     });
   }