useFragmentInternal should suspend if environment changes and there is a query in flight

Summary:
There is a bug in the new hooks implementation, where the `useFragmentInternal` would not suspend after the change of the environment (while the fragment selector are the same) with the active operation in flight.

This diff fixes that by checking if the environment has changed and we would throw the promise for pending operation in flight.

Reviewed By: voideanvalue

Differential Revision: D52516772

fbshipit-source-id: 13a61114e6b7718af548cf45d2e4685bcd121993

Author: alunyov

packages/react-relay/relay-hooks/__tests__/useFragmentNode-test.js

@@ -661,6 +661,33 @@ describe.each([
       ]);
     });
 
+    it('should supsend when the environment changes and there is query in flight', () => {
+      const renderer = renderSingularFragment();
+      assertFragmentResults([
+        {
+          data: {
+            id: '1',
+            name: 'Alice',
+            profile_picture: null,
+            ...createFragmentRef('1', singularQuery),
+          },
+        },
+      ]);
+
+      const newEnvironment = createMockEnvironment();
+
+      internalAct(() => {
+        // Let there be an operation in flight
+        fetchQuery(newEnvironment, singularQuery).subscribe({});
+
+        setEnvironment(newEnvironment);
+      });
+
+      // It should suspend when the environment changes and there is a query
+      // in flight.
+      expect(renderer.toJSON()).toEqual('Singular Fallback');
+    });
+
     it('should re-read and resubscribe to fragment when fragment pointers change', () => {
       renderSingularFragment();
       assertRenderBatch([

packages/react-relay/relay-hooks/experimental/useFragmentInternal_EXPERIMENTAL.js

@@ -505,6 +505,7 @@ function useFragmentInternal_EXPERIMENTAL(
     // We only suspend when the component is first trying to mount or changing
     // selectors, not if data becomes missing later:
     if (
+      environment !== previousEnvironment ||
       !committedFragmentSelectorRef.current ||
       !areEqualSelectors(committedFragmentSelectorRef.current, fragmentSelector)
     ) {