From 3f8687e1f51cc48efbf6be3f0677f5bd06ecba08 Mon Sep 17 00:00:00 2001
From: dizel3d <dizel3d@yandex-team.ru>
Date: Tue, 28 Jan 2020 00:24:34 +0300
Subject: [PATCH] fix(useIntersection): reset an intersectionObserverEntry when
 the ref changes

---
 src/useIntersection.ts         |  5 ++++-
 tests/useIntersection.test.tsx | 29 +++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/useIntersection.ts b/src/useIntersection.ts
index 531ce3fb..aec578f4 100644
--- a/src/useIntersection.ts
+++ b/src/useIntersection.ts
@@ -15,7 +15,10 @@ const useIntersection = (
       const observer = new IntersectionObserver(handler, options);
       observer.observe(ref.current);
 
-      return () => observer.disconnect();
+      return () => {
+        setIntersectionObserverEntry(null);
+        observer.disconnect();
+      };
     }
     return () => {};
   }, [ref.current, options.threshold, options.root, options.rootMargin]);
diff --git a/tests/useIntersection.test.tsx b/tests/useIntersection.test.tsx
index b8cdde7b..cdd3d9e8 100644
--- a/tests/useIntersection.test.tsx
+++ b/tests/useIntersection.test.tsx
@@ -49,6 +49,35 @@ describe('useIntersection', () => {
     expect(result.current).toBe(null);
   });
 
+  it('should reset an intersectionObserverEntry when the ref changes', () => {
+    TestUtils.act(() => {
+      targetRef = createRef();
+      ReactDOM.render(<div ref={targetRef} />, container);
+    });
+
+    const { result, rerender } = renderHook(() => useIntersection(targetRef, { root: container, threshold: 0.8 }));
+
+    const mockIntersectionObserverEntry = {
+      boundingClientRect: targetRef.current.getBoundingClientRect(),
+      intersectionRatio: 0.81,
+      intersectionRect: container.getBoundingClientRect(),
+      isIntersecting: true,
+      rootBounds: container.getBoundingClientRect(),
+      target: targetRef.current,
+      time: 300,
+    };
+    TestRenderer.act(() => {
+      intersectionObserver.simulate(mockIntersectionObserverEntry);
+    });
+
+    expect(result.current).toEqual(mockIntersectionObserverEntry);
+
+    targetRef.current = document.createElement('div');
+    rerender();
+
+    expect(result.current).toEqual(null);
+  });
+
   it('should disconnect an old IntersectionObserver instance when the ref changes', () => {
     targetRef = createRef();
     targetRef.current = document.createElement('div');