Add a feature flag to disable legacy context

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

@@ -0,0 +1,110 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react-core
+ */
+
+'use strict';
+
+let React;
+let ReactDOM;
+let ReactFeatureFlags;
+
+describe('ReactLegacyContextDisabled', () => {
+  beforeEach(() => {
+    jest.resetModules();
+
+    React = require('react');
+    ReactDOM = require('react-dom');
+    ReactFeatureFlags = require('shared/ReactFeatureFlags');
+    ReactFeatureFlags.disableLegacyContext = true;
+  });
+
+  it('throws for a legacy context provider', () => {
+    class Provider extends React.Component {
+      static childContextTypes = {
+        foo() {},
+      };
+      getChildContext() {
+        return {foo: 10};
+      }
+      render() {
+        return null;
+      }
+    }
+
+    const container = document.createElement('div');
+    expect(() => {
+      ReactDOM.render(<Provider />, container);
+    }).toThrow(
+      'The legacy childContextTypes API is no longer supported. ' +
+        'Use React.createContext() instead.',
+    );
+  });
+
+  it('throws for a legacy context consumer', () => {
+    class Consumer extends React.Component {
+      static contextTypes = {
+        foo() {},
+      };
+      render() {
+        return null;
+      }
+    }
+
+    const container = document.createElement('div');
+    expect(() => {
+      ReactDOM.render(<Consumer />, container);
+    }).toThrow(
+      'The legacy contextTypes API is no longer supported. ' +
+        'Use React.createContext() with contextType instead.',
+    );
+  });
+
+  it('renders a tree with modern context', () => {
+    let Ctx = React.createContext();
+
+    class Provider extends React.Component {
+      render() {
+        return (
+          <Ctx.Provider value={this.props.value}>
+            {this.props.children}
+          </Ctx.Provider>
+        );
+      }
+    }
+
+    class RenderPropConsumer extends React.Component {
+      render() {
+        return <Ctx.Consumer>{value => value}</Ctx.Consumer>;
+      }
+    }
+
+    class ContextTypeConsumer extends React.Component {
+      static contextType = Ctx;
+      render() {
+        return this.context;
+      }
+    }
+
+    function FnConsumer() {
+      return React.useContext(Ctx);
+    }
+
+    const container = document.createElement('div');
+    ReactDOM.render(
+      <Provider value="a">
+        <span>
+          <RenderPropConsumer />
+          <ContextTypeConsumer />
+          <FnConsumer />
+        </span>
+      </Provider>,
+      container,
+    );
+    expect(container.textContent).toBe('aaa');
+  });
+});