Fix incorrect legacy context for factory components

packages/react-reconciler/src/ReactFiberBeginWork.js

@@ -262,7 +262,7 @@ function updateFunctionalComponent(
   nextProps: any,
   renderExpirationTime,
 ) {
-  const unmaskedContext = getUnmaskedContext(workInProgress, Component);
+  const unmaskedContext = getUnmaskedContext(workInProgress, Component, true);
   const context = getMaskedContext(workInProgress, unmaskedContext);
 
   let nextChildren;
@@ -674,7 +674,7 @@ function mountIndeterminateComponent(
     }
   }
 
-  const unmaskedContext = getUnmaskedContext(workInProgress, Component);
+  const unmaskedContext = getUnmaskedContext(workInProgress, Component, false);
   const context = getMaskedContext(workInProgress, unmaskedContext);
 
   prepareToReadContext(workInProgress, renderExpirationTime);

packages/react-reconciler/src/ReactFiberClassComponent.js

@@ -473,7 +473,7 @@ function constructClassInstance(
   props: any,
   renderExpirationTime: ExpirationTime,
 ): any {
-  const unmaskedContext = getUnmaskedContext(workInProgress, ctor);
+  const unmaskedContext = getUnmaskedContext(workInProgress, ctor, true);
   const contextTypes = ctor.contextTypes;
   const isContextConsumer = contextTypes !== null && contextTypes !== undefined;
   const context = isContextConsumer
@@ -666,7 +666,7 @@ function mountClassInstance(
   }
 
   const instance = workInProgress.stateNode;
-  const unmaskedContext = getUnmaskedContext(workInProgress, ctor);
+  const unmaskedContext = getUnmaskedContext(workInProgress, ctor, true);
 
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
@@ -758,7 +758,11 @@ function resumeMountClassInstance(
   instance.props = oldProps;
 
   const oldContext = instance.context;
-  const nextLegacyUnmaskedContext = getUnmaskedContext(workInProgress, ctor);
+  const nextLegacyUnmaskedContext = getUnmaskedContext(
+    workInProgress,
+    ctor,
+    true,
+  );
   const nextLegacyContext = getMaskedContext(
     workInProgress,
     nextLegacyUnmaskedContext,
@@ -897,7 +901,11 @@ function updateClassInstance(
   instance.props = oldProps;
 
   const oldContext = instance.context;
-  const nextLegacyUnmaskedContext = getUnmaskedContext(workInProgress, ctor);
+  const nextLegacyUnmaskedContext = getUnmaskedContext(
+    workInProgress,
+    ctor,
+    true,
+  );
   const nextLegacyContext = getMaskedContext(
     workInProgress,
     nextLegacyUnmaskedContext,

packages/react-reconciler/src/ReactFiberContext.js

@@ -49,11 +49,11 @@ let previousContext: Object = emptyContextObject;
 function getUnmaskedContext(
   workInProgress: Fiber,
   Component: Function,
+  didPushOwnContextIfProvider: boolean,
 ): Object {
-  const hasOwnContext = isContextProvider(Component);
-  if (hasOwnContext) {
+  if (didPushOwnContextIfProvider && isContextProvider(Component)) {
     // If the fiber is a context provider itself, when we read its context
-    // we have already pushed its own child context on the stack. A context
+    // we may have already pushed its own child context on the stack. A context
     // provider should not "see" its own child context. Therefore we read the
     // previous (parent) context instead for a context provider.
     return previousContext;

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

@@ -2030,6 +2030,39 @@ describe('ReactIncremental', () => {
     ]);
   });
 
+  it('does not leak own context into context provider (factory components)', () => {
+    const ops = [];
+    function Recurse(props, context) {
+      return {
+        getChildContext() {
+          return {n: (context.n || 3) - 1};
+        },
+        render() {
+          ops.push('Recurse ' + JSON.stringify(context));
+          if (context.n === 0) {
+            return null;
+          }
+          return <Recurse />;
+        },
+      };
+    }
+    Recurse.contextTypes = {
+      n: PropTypes.number,
+    };
+    Recurse.childContextTypes = {
+      n: PropTypes.number,
+    };
+
+    ReactNoop.render(<Recurse />);
+    ReactNoop.flush();
+    expect(ops).toEqual([
+      'Recurse {}',
+      'Recurse {"n":2}',
+      'Recurse {"n":1}',
+      'Recurse {"n":0}',
+    ]);
+  });
+
   it('provides context when reusing work', () => {
     const ops = [];