From 1eb42b451c6d06885061d7f9a5a7695485db6902 Mon Sep 17 00:00:00 2001
From: FAL-coffee <fal.engineer.2001@gmail.com>
Date: Mon, 9 Jun 2025 14:39:52 +0900
Subject: [PATCH] add parallelLimit option for SWRInfinite

---
 src/infinite/index.ts          | 20 ++++++++++--
 src/infinite/types.ts          |  1 +
 test/use-swr-infinite.test.tsx | 59 ++++++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 3 deletions(-)

diff --git a/src/infinite/index.ts b/src/infinite/index.ts
index 4292ea4486..d2a27c88ca 100644
--- a/src/infinite/index.ts
+++ b/src/infinite/index.ts
@@ -56,7 +56,8 @@ export const infinite = (<Data, Error>(useSWRNext: SWRHook) =>
       persistSize = false,
       revalidateFirstPage = true,
       revalidateOnMount = false,
-      parallel = false
+      parallel = false,
+      parallelLimit
     } = config
     const [, , , PRELOAD] = SWRGlobalState.get(defaultCache) as GlobalState
 
@@ -215,9 +216,22 @@ export const infinite = (<Data, Error>(useSWRNext: SWRHook) =>
           }
         }
 
-        // flush all revalidateions in parallel
+        // flush all revalidations in parallel with optional limit
         if (parallel) {
-          await Promise.all(revalidators.map(r => r()))
+          if (
+            parallelLimit &&
+            parallelLimit > 0 &&
+            revalidators.length > parallelLimit
+          ) {
+            // Process in batches with limited concurrency
+            for (let i = 0; i < revalidators.length; i += parallelLimit) {
+              const batch = revalidators.slice(i, i + parallelLimit)
+              await Promise.all(batch.map(r => r()))
+            }
+          } else {
+            // Traditional full parallel execution
+            await Promise.all(revalidators.map(r => r()))
+          }
         }
 
         // once we executed the data fetching based on the context, clear the context
diff --git a/src/infinite/types.ts b/src/infinite/types.ts
index 4237b6abae..1266ad2a70 100644
--- a/src/infinite/types.ts
+++ b/src/infinite/types.ts
@@ -39,6 +39,7 @@ export interface SWRInfiniteConfiguration<
   persistSize?: boolean
   revalidateFirstPage?: boolean
   parallel?: boolean
+  parallelLimit?: number
   fetcher?: Fn
   compare?: SWRInfiniteCompareFn<Data>
 }
diff --git a/test/use-swr-infinite.test.tsx b/test/use-swr-infinite.test.tsx
index cec8e7f462..d9afaa9974 100644
--- a/test/use-swr-infinite.test.tsx
+++ b/test/use-swr-infinite.test.tsx
@@ -1812,6 +1812,65 @@ describe('useSWRInfinite', () => {
     screen.getByText('data:apple, banana, pineapple,')
   })
 
+  it('should support the parallelLimit option', async () => {
+    // mock api with delay tracking
+    const pageData = [
+      'apple',
+      'banana',
+      'pineapple',
+      'orange',
+      'grape',
+      'cherry'
+    ]
+    const requestGroups: number[][] = []
+    let currentBatch: number[] = []
+    let batchStartTime = 0
+
+    const key = createKey()
+    function Page() {
+      const { data } = useSWRInfinite(
+        index => [key, index],
+        async ([_, index]) => {
+          const now = Date.now()
+          // Start a new batch if this is the first request or if more than 10ms has passed since the last batch
+          if (currentBatch.length === 0 || now - batchStartTime > 10) {
+            if (currentBatch.length > 0) {
+              requestGroups.push([...currentBatch])
+            }
+            currentBatch = [index]
+            batchStartTime = now
+          } else {
+            currentBatch.push(index)
+          }
+          return createResponse(`${pageData[index]}, `, { delay: 50 })
+        },
+        {
+          initialSize: 6,
+          parallel: true,
+          parallelLimit: 2
+        }
+      )
+
+      return <div>data:{data}</div>
+    }
+
+    renderWithConfig(<Page />)
+    screen.getByText('data:')
+
+    // Wait for all requests to complete
+    await act(() => sleep(300))
+    screen.getByText('data:apple, banana, pineapple, orange, grape, cherry,')
+
+    // Push the last batch if it's not empty
+    if (currentBatch.length > 0) {
+      requestGroups.push([...currentBatch])
+    }
+
+    // Verify that requests were made in batches of 2
+    expect(requestGroups.length).toBeGreaterThanOrEqual(3) // Should have at least 3 batches for 6 items with limit 2
+    expect(requestGroups.every(batch => batch.length <= 2)).toBeTruthy() // Each batch should have at most 2 items
+  })
+
   it('should make previousPageData null when the parallel option is enabled', async () => {
     // mock api
     const pageData = ['apple', 'banana', 'pineapple']