feat: honor displayName of context types (facebook#18224)

* Revert "Revert "feat: honor displayName of context types (facebook#18035)" (facebook#18223)"

This reverts commit 3ee812e.

* Add warning of displayName is set on the consumer

* dedupe warning

Author: Brian Vaughn

packages/react/src/ReactContext.js

@@ -57,6 +57,7 @@ export function createContext<T>(
 
   let hasWarnedAboutUsingNestedContextConsumers = false;
   let hasWarnedAboutUsingConsumerProvider = false;
+  let hasWarnedAboutDisplayNameOnConsumer = false;
 
   if (__DEV__) {
     // A separate object, but proxies back to the original context object for
@@ -120,6 +121,20 @@ export function createContext<T>(
           return context.Consumer;
         },
       },
+      displayName: {
+        get() {
+          return context.displayName;
+        },
+        set() {
+          if (!hasWarnedAboutDisplayNameOnConsumer) {
+            console.warn(
+              'Setting `displayName` on Context.Consumer has no effect. ' +
+                "You should set it directly on the context with Context.displayName = 'NamedContext'.",
+            );
+            hasWarnedAboutDisplayNameOnConsumer = true;
+          }
+        },
+      },
     });
     // $FlowFixMe: Flow complains about missing properties because it doesn't understand defineProperty
     context.Consumer = Consumer;

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

@@ -18,6 +18,7 @@
 let PropTypes;
 let React;
 let ReactDOM;
+let ReactDOMServer;
 let ReactTestUtils;
 
 describe('ReactContextValidator', () => {
@@ -27,6 +28,7 @@ describe('ReactContextValidator', () => {
     PropTypes = require('prop-types');
     React = require('react');
     ReactDOM = require('react-dom');
+    ReactDOMServer = require('react-dom/server');
     ReactTestUtils = require('react-dom/test-utils');
   });
 
@@ -671,4 +673,41 @@ describe('ReactContextValidator', () => {
       'Warning: ComponentB: Function components do not support contextType.',
     );
   });
+
+  it('should honor a displayName if set on the context type', () => {
+    const Context = React.createContext(null);
+    Context.displayName = 'MyContextType';
+    function Validator() {
+      return null;
+    }
+    Validator.propTypes = {dontPassToSeeErrorStack: PropTypes.bool.isRequired};
+
+    expect(() => {
+      ReactDOMServer.renderToStaticMarkup(
+        <Context.Provider>
+          <Context.Consumer>{() => <Validator />}</Context.Consumer>
+        </Context.Provider>,
+      );
+    }).toErrorDev(
+      'Warning: Failed prop type: The prop `dontPassToSeeErrorStack` is marked as required in `Validator`, but its value is `undefined`.\n' +
+        '    in Validator (at **)\n' +
+        '    in MyContextType.Consumer (at **)\n' +
+        '    in MyContextType.Provider (at **)',
+    );
+  });
+
+  it('warns if displayName is set on the consumer type', () => {
+    const Context = React.createContext(null);
+
+    expect(() => {
+      Context.Consumer.displayName = 'ignored';
+    }).toWarnDev(
+      'Warning: Setting `displayName` on Context.Consumer has no effect. ' +
+        "You should set it directly on the context with Context.displayName = 'NamedContext'.",
+      {withoutStack: true},
+    );
+
+    // warning is deduped so subsequent setting is fine
+    Context.Consumer.displayName = 'ignored';
+  });
 });

packages/shared/getComponentName.js

@@ -24,6 +24,7 @@ import {
   REACT_BLOCK_TYPE,
 } from 'shared/ReactSymbols';
 import {refineResolvedLazyComponent} from 'shared/ReactLazyComponent';
+import type {ReactContext, ReactProviderType} from 'shared/ReactTypes';
 
 function getWrappedName(
   outerType: mixed,
@@ -37,6 +38,10 @@ function getWrappedName(
   );
 }
 
+function getContextName(type: ReactContext<any>) {
+  return type.displayName || 'Context';
+}
+
 function getComponentName(type: mixed): string | null {
   if (type == null) {
     // Host root, text node or just invalid type.
@@ -73,9 +78,11 @@ function getComponentName(type: mixed): string | null {
   if (typeof type === 'object') {
     switch (type.$$typeof) {
       case REACT_CONTEXT_TYPE:
-        return 'Context.Consumer';
+        const context: ReactContext<any> = (type: any);
+        return getContextName(context) + '.Consumer';
       case REACT_PROVIDER_TYPE:
-        return 'Context.Provider';
+        const provider: ReactProviderType<any> = (type: any);
+        return getContextName(provider._context) + '.Provider';
       case REACT_FORWARD_REF_TYPE:
         return getWrappedName(type, type.render, 'ForwardRef');
       case REACT_MEMO_TYPE: