[Fast Refresh] Fix for intentional unmounts after an error (#17368)

packages/react-refresh/src/ReactFreshRuntime.js

@@ -468,6 +468,10 @@ export function injectIntoGlobalHook(globalObject: any): void {
             // TODO: Maybe we could fix this as the same time as when we fix
             // DevTools to not depend on `alternate.memoizedState.element`.
             didSomeRootFailOnMount = true;
+          } else if (!didError && failedRoots.has(root)) {
+            // The error is fixed but the component is still unmounted.
+            // This means that the unmount was not caused by a failed refresh.
+            failedRoots.delete(root);
           }
         }
       } else {

packages/react-refresh/src/__tests__/ReactFresh-test.js

@@ -2870,6 +2870,42 @@ describe('ReactFresh', () => {
       });
       expect(container.innerHTML).toBe('');
       expect(ReactFreshRuntime.hasUnrecoverableErrors()).toBe(false);
+
+      // Mount a new container.
+      render(() => {
+        function Hello() {
+          return <h1>Hi</h1>;
+        }
+        $RefreshReg$(Hello, 'Hello');
+
+        return Hello;
+      });
+      expect(container.innerHTML).toBe('<h1>Hi</h1>');
+      expect(ReactFreshRuntime.hasUnrecoverableErrors()).toBe(false);
+
+      // Break again.
+      expect(() => {
+        patch(() => {
+          function Hello() {
+            throw new Error('Oops');
+          }
+          $RefreshReg$(Hello, 'Hello');
+        });
+      }).toThrow('Oops');
+      expect(container.innerHTML).toBe('');
+      expect(ReactFreshRuntime.hasUnrecoverableErrors()).toBe(false);
+
+      // Check we don't attempt to reverse an intentional unmount, even after an error.
+      ReactDOM.unmountComponentAtNode(container);
+      expect(container.innerHTML).toBe('');
+      patch(() => {
+        function Hello() {
+          return <h1>Never mind me!</h1>;
+        }
+        $RefreshReg$(Hello, 'Hello');
+      });
+      expect(container.innerHTML).toBe('');
+      expect(ReactFreshRuntime.hasUnrecoverableErrors()).toBe(false);
     }
   });