add comment for guards added in useEffects

isographlabs · Jan 3, 2025 · c8d6a76 · c8d6a76
1 parent ef89d4d
commit c8d6a76
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diff --git a/libs/isograph-react-disposable-state/src/useCachedResponsivePrecommitValue.ts b/libs/isograph-react-disposable-state/src/useCachedResponsivePrecommitValue.ts
@@ -51,6 +51,10 @@ export function useCachedResponsivePrecommitValue<T>(
   const lastCommittedParentCache = useRef<ParentCache<T> | null>(null);
 
   useEffect(() => {
+    // react reruns all `useEffect` in HMR since it doesn't know if the
+    // code inside of useEffect has changed. Since this is a library
+    // user can't change this code so we are safe to skip this rerun.
+    // This also prevents `useEffect` from running twice in Strict Mode.
     if (lastCommittedParentCache.current === parentCache) {
       return;
     }

diff --git a/libs/isograph-react-disposable-state/src/useLazyDisposableState.ts b/libs/isograph-react-disposable-state/src/useLazyDisposableState.ts
@@ -32,6 +32,10 @@ export function useLazyDisposableState<T>(
 
   const lastCommittedParentCache = useRef<ParentCache<T> | null>(null);
   useEffect(() => {
+    // react reruns all `useEffect` in HMR since it doesn't know if the
+    // code inside of useEffect has changed. Since this is a library
+    // user can't change this code so we are safe to skip this rerun.
+    // This also prevents `useEffect` from running twice in Strict Mode.
     if (lastCommittedParentCache.current === parentCache) {
       return;
     }