[DevTools] [Context] Legacy Context (#16617)

* Added hasLegacyContext check.

* Passed hasLegacyContext as prop to SelectedElement

* Changing context labels based on hasLegacyContext

* Fixed flow types.

* Fixed typos.

* Added tests for hasLegacyContext.

* Renamed test.

* Removed test imports.

packages/react-devtools-shared/src/__tests__/inspectedElementContext-test.js

@@ -15,6 +15,7 @@ import type Store from 'react-devtools-shared/src/devtools/store';
 describe('InspectedElementContext', () => {
   let React;
   let ReactDOM;
+  let PropTypes;
   let TestRenderer: ReactTestRenderer;
   let bridge: FrontendBridge;
   let store: Store;
@@ -40,6 +41,7 @@ describe('InspectedElementContext', () => {
 
     React = require('react');
     ReactDOM = require('react-dom');
+    PropTypes = require('prop-types');
     TestUtils = require('react-dom/test-utils');
     TestRenderer = utils.requireTestRenderer();
 
@@ -114,6 +116,119 @@ describe('InspectedElementContext', () => {
     done();
   });
 
+  it('should have hasLegacyContext flag set to either "true" or "false" depending on which context API is used.', async done => {
+    const contextData = {
+      bool: true,
+    };
+
+    // Legacy Context API.
+    class LegacyContextProvider extends React.Component<any> {
+      static childContextTypes = {
+        bool: PropTypes.bool,
+      };
+      getChildContext() {
+        return contextData;
+      }
+      render() {
+        return this.props.children;
+      }
+    }
+    class LegacyContextConsumer extends React.Component<any> {
+      static contextTypes = {
+        bool: PropTypes.bool,
+      };
+      render() {
+        return null;
+      }
+    }
+
+    // Modern Context API
+    const BoolContext = React.createContext(contextData.bool);
+    BoolContext.displayName = 'BoolContext';
+
+    class ModernContextType extends React.Component<any> {
+      static contextType = BoolContext;
+      render() {
+        return null;
+      }
+    }
+
+    const ModernContext = React.createContext();
+    ModernContext.displayName = 'ModernContext';
+
+    const container = document.createElement('div');
+    await utils.actAsync(() =>
+      ReactDOM.render(
+        <React.Fragment>
+          <LegacyContextProvider>
+            <LegacyContextConsumer />
+          </LegacyContextProvider>
+          <BoolContext.Consumer>{value => null}</BoolContext.Consumer>
+          <ModernContextType />
+          <ModernContext.Provider value={contextData}>
+            <ModernContext.Consumer>{value => null}</ModernContext.Consumer>
+          </ModernContext.Provider>
+        </React.Fragment>,
+        container,
+      ),
+    );
+
+    const ids = [
+      {
+        // <LegacyContextConsumer />
+        id: ((store.getElementIDAtIndex(1): any): number),
+        shouldHaveLegacyContext: true,
+      },
+      {
+        // <BoolContext.Consumer>
+        id: ((store.getElementIDAtIndex(2): any): number),
+        shouldHaveLegacyContext: false,
+      },
+      {
+        // <ModernContextType />
+        id: ((store.getElementIDAtIndex(3): any): number),
+        shouldHaveLegacyContext: false,
+      },
+      {
+        // <ModernContext.Consumer>
+        id: ((store.getElementIDAtIndex(5): any): number),
+        shouldHaveLegacyContext: false,
+      },
+    ];
+
+    function Suspender({target, shouldHaveLegacyContext}) {
+      const {getInspectedElement} = React.useContext(InspectedElementContext);
+      const inspectedElement = getInspectedElement(target);
+
+      expect(inspectedElement.context).not.toBe(null);
+      expect(inspectedElement.hasLegacyContext).toBe(shouldHaveLegacyContext);
+
+      return null;
+    }
+
+    for (let i = 0; i < ids.length; i++) {
+      const {id, shouldHaveLegacyContext} = ids[i];
+
+      await utils.actAsync(
+        () =>
+          TestRenderer.create(
+            <Contexts
+              defaultSelectedElementID={id}
+              defaultSelectedElementIndex={0}>
+              <React.Suspense fallback={null}>
+                <Suspender
+                  target={id}
+                  shouldHaveLegacyContext={shouldHaveLegacyContext}
+                />
+              </React.Suspense>
+            </Contexts>,
+          ),
+        false,
+      );
+    }
+    done();
+  });
+
   it('should poll for updates for the currently selected element', async done => {
     const Example = () => null;
 

packages/react-devtools-shared/src/backend/legacy/renderer.js

@@ -753,6 +753,9 @@ export function attach(
       // Can view component source location.
       canViewSource: type === ElementTypeClass || type === ElementTypeFunction,
 
+      // Only legacy context exists in legacy versions.
+      hasLegacyContext: true,
+
       displayName: displayName,
 
       type: type,

packages/react-devtools-shared/src/backend/renderer.js

@@ -2107,6 +2107,8 @@ export function attach(
       type,
     } = fiber;
 
+    const elementType = getElementTypeForFiber(fiber);
+
     const usesHooks =
       (tag === FunctionComponent ||
         tag === SimpleMemoComponent ||
@@ -2128,7 +2130,14 @@ export function attach(
     ) {
       canViewSource = true;
       if (stateNode && stateNode.context != null) {
-        context = stateNode.context;
+        // Don't show an empty context object for class components that don't use the context API.
+        const shouldHideContext =
+          elementType === ElementTypeClass &&
+          !(type.contextTypes || type.contextType);
+
+        if (!shouldHideContext) {
+          context = stateNode.context;
+        }
       }
     } else if (
       typeSymbol === CONTEXT_CONSUMER_NUMBER ||
@@ -2166,7 +2175,10 @@ export function attach(
       }
     }
 
+    let hasLegacyContext = false;
     if (context !== null) {
+      hasLegacyContext = !!type.contextTypes;
+
       // To simplify hydration and display logic for context, wrap in a value object.
       // Otherwise simple values (e.g. strings, booleans) become harder to handle.
       context = {value: context};
@@ -2238,8 +2250,11 @@ export function attach(
       // Can view component source location.
       canViewSource,
 
+      // Does the component have legacy context attached to it.
+      hasLegacyContext,
+
       displayName: getDisplayNameForFiber(fiber),
-      type: getElementTypeForFiber(fiber),
+      type: elementType,
 
       // Inspectable properties.
       // TODO Review sanitization approach for the below inspectable values.

packages/react-devtools-shared/src/backend/types.js

@@ -163,6 +163,9 @@ export type InspectedElement = {|
   // Can view component source location.
   canViewSource: boolean,
 
+  // Does the component have legacy context attached to it.
+  hasLegacyContext: boolean,
+
   // Inspectable properties.
   context: Object | null,
   hooks: Object | null,

packages/react-devtools-shared/src/devtools/views/Components/InspectedElementContext.js

@@ -159,6 +159,7 @@ function InspectedElementContextController({children}: Props) {
               canEditHooks,
               canToggleSuspense,
               canViewSource,
+              hasLegacyContext,
               source,
               type,
               owners,
@@ -173,6 +174,7 @@ function InspectedElementContextController({children}: Props) {
               canEditHooks,
               canToggleSuspense,
               canViewSource,
+              hasLegacyContext,
               id,
               source,
               type,

packages/react-devtools-shared/src/devtools/views/Components/SelectedElement.js

@@ -267,6 +267,7 @@ function InspectedElementView({
     canEditFunctionProps,
     canEditHooks,
     canToggleSuspense,
+    hasLegacyContext,
     context,
     hooks,
     owners,
@@ -376,7 +377,7 @@ function InspectedElementView({
       )}
       <HooksTree canEditHooks={canEditHooks} hooks={hooks} id={id} />
       <InspectedElementTree
-        label="context"
+        label={hasLegacyContext ? 'legacy context' : 'context'}
         data={context}
         inspectPath={inspectContextPath}
         overrideValueFn={overrideContextFn}

packages/react-devtools-shared/src/devtools/views/Components/types.js

@@ -71,6 +71,9 @@ export type InspectedElement = {|
   // Can view component source location.
   canViewSource: boolean,
 
+  // Does the component have legacy context attached to it.
+  hasLegacyContext: boolean,
+
   // Inspectable properties.
   context: Object | null,
   hooks: Object | null,
@@ -80,7 +83,7 @@ export type InspectedElement = {|
   // List of owners
   owners: Array<Owner> | null,
 
-  // Location of component in source coude.
+  // Location of component in source code.
   source: Source | null,
 
   type: ElementType,