fix

_internal/utils/mutate.ts

@@ -86,15 +86,15 @@ export const internalMutate = async <Data>(
   // Do optimistic data update.
   if (hasOptimisticData) {
     optimisticData = isFunction(optimisticData)
-      ? optimisticData(currentData)
+      ? optimisticData(originalData)
       : optimisticData
     set({ data: optimisticData, _o: originalData })
   }
 
   if (isFunction(data)) {
     // `data` is a function, call it passing current cache value.
     try {
-      data = (data as MutatorCallback<Data>)(currentData)
+      data = (data as MutatorCallback<Data>)(originalData)
     } catch (err) {
       // If it throws an error synchronously, we shouldn't update the cache.
       error = err
@@ -129,7 +129,7 @@ export const internalMutate = async <Data>(
     if (!error) {
       // Transform the result into data.
       if (isFunction(populateCache)) {
-        data = populateCache(data, currentData)
+        data = populateCache(data, originalData)
       }
 
       // Only update cached data if there's no error. Data can be `undefined` here.

test/use-swr-local-mutation.test.tsx

@@ -1193,9 +1193,9 @@ describe('useSWR - local mutation', () => {
     // It should revert to `0` instead of `1` at the end.
     expect(renderedData).toEqual([undefined, 0, 1, 2, 0])
 
-    // It should receive the latest displayed data instead of the original data.
-    expect(previousValue).toBe(1)
-    expect(previousValue2).toBe(1)
+    // It should receive the original displayed data instead of current displayed data.
+    expect(previousValue).toBe(0)
+    expect(previousValue2).toBe(0)
   })
 
   it('should not rollback optimistic updates if `rollbackOnError`', async () => {