perf(renderer): release unrelated state during cache saves (#23021)

src/renderer/src/store/github/cache-persistence.test.ts

@@ -0,0 +1,64 @@
+import { setImmediate } from 'node:timers/promises'
+import { afterEach, beforeEach, expect, it, vi } from 'vitest'
+import { createTestStore } from '../slices/store-test-helpers'
+import { debouncedSaveCache } from './cache-persistence'
+
+const setGitHub = vi.fn()
+
+beforeEach(() => {
+  vi.useFakeTimers({ toFake: ['setTimeout', 'clearTimeout'] })
+  setGitHub.mockReset()
+  vi.stubGlobal('window', { api: { cache: { setGitHub } } })
+})
+
+afterEach(() => {
+  vi.clearAllTimers()
+  vi.useRealTimers()
+  vi.unstubAllGlobals()
+})
+
+it('releases unrelated discarded renderer state while the cache save is pending', async () => {
+  const store = createTestStore()
+  const schedule = () => {
+    const drafts = { closedFile: Buffer.alloc(8 * 1024 * 1024, 65).toString('utf8') }
+    const state = { ...store.getState(), editorDrafts: drafts }
+    debouncedSaveCache(state)
+    return { state: new WeakRef(state), drafts: new WeakRef(drafts) }
+  }
+  const discarded = schedule()
+  if (!global.gc) {
+    throw new Error('config/vitest.config.ts must pass --expose-gc')
+  }
+  for (let turn = 0; turn < 3; turn += 1) {
+    await setImmediate()
+    global.gc()
+  }
+
+  expect(setGitHub).not.toHaveBeenCalled()
+  expect(discarded.state.deref() === undefined).toBe(true)
+  expect(discarded.drafts.deref() === undefined).toBe(true)
+  vi.advanceTimersByTime(1000)
+  expect(setGitHub).toHaveBeenCalledOnce()
+})
+
+it('persists the latest requested cache maps once after the trailing second', () => {
+  const state = createTestStore().getState()
+  const first = { ...state, prCache: {}, issueCache: {} }
+  const latest = { ...state, prCache: {}, issueCache: {} }
+  debouncedSaveCache(first)
+  vi.advanceTimersByTime(999)
+  expect(setGitHub).not.toHaveBeenCalled()
+
+  debouncedSaveCache(latest)
+  vi.advanceTimersByTime(999)
+  expect(setGitHub).not.toHaveBeenCalled()
+  vi.advanceTimersByTime(1)
+  expect(setGitHub).toHaveBeenCalledOnce()
+  expect(setGitHub.mock.calls[0][0]).toEqual({
+    cache: { pr: latest.prCache, issue: latest.issueCache }
+  })
+  expect(setGitHub.mock.calls[0][0].cache.pr).toBe(latest.prCache)
+  expect(setGitHub.mock.calls[0][0].cache.issue).toBe(latest.issueCache)
+  vi.advanceTimersByTime(1000)
+  expect(setGitHub).toHaveBeenCalledOnce()
+})

src/renderer/src/store/github/cache-persistence.ts

@@ -5,12 +5,14 @@ let saveTimer: ReturnType<typeof setTimeout> | null = null
 /** Schedules the renderer's single trailing GitHub cache persistence write. */
 export function debouncedSaveCache(state: AppState): void {
   clearTimeout(saveTimer ?? undefined)
+  // Keep unrelated renderer state out of the pending timer's closure.
+  const { prCache, issueCache } = state
   saveTimer = setTimeout(() => {
     saveTimer = null
     window.api.cache.setGitHub({
       cache: {
-        pr: state.prCache,
-        issue: state.issueCache
+        pr: prCache,
+        issue: issueCache
       }
     })
   }, 1000)