test: prove diff reveal cancels a paging rail jump (#29585)

Co-authored-by: OrcaWin <293788423+OrcaWin@users.noreply.github.com>

src/renderer/src/components/native-chat/NativeChatMessageList.rail-history-jump.test.tsx

@@ -44,7 +44,6 @@ import {
   layout,
   marker,
   overrideLayoutProperty,
-  scrollTranscript,
   session,
   stubLayout,
   stubResizeObserver
@@ -270,8 +269,10 @@ describe('jumping from the rail while following the end', () => {
     fireEvent.click(screen.getByRole('button', { name: prompt }))
     if (loaded) {
       expect(Math.abs(rowOffsetFromViewportTop(prompt))).toBeLessThanOrEqual(2)
+      await frame()
+      expect(Math.abs(rowOffsetFromViewportTop(prompt))).toBeLessThanOrEqual(2)
     }
-    await settle(60)
+    await settle(loaded ? 59 : 60)
 
     expect(HTMLElement.prototype.scrollTo).toHaveBeenCalled()
     expect(HTMLElement.prototype.scrollTo).not.toHaveBeenCalledWith(
@@ -424,115 +425,109 @@ describe('jumping from the rail while following the end', () => {
     expect(distanceFromBottom()).toBe(0)
   })
 
-  it('lands a jump to a loaded message within one frame', async () => {
-    render(<PagedTranscript />)
-    await settle(10)
-
-    fireEvent.click(screen.getByRole('button', { name: 'prompt-45' }))
-    await frame()
-
-    // A smooth scroll would still be easing in here, a few pixels from where it started.
-    expect(Math.abs(rowOffsetFromViewportTop('prompt-45'))).toBeLessThanOrEqual(2)
-  })
-})
-
-describe('revealing a diff while a rail jump pages', () => {
-  let restoreLayout = (): void => {}
-  beforeEach(() => {
-    restoreLayout = stubLayout()
-  })
-  afterEach(() => {
-    restoreLayout()
-    vi.restoreAllMocks()
-  })
-
-  function journalItem(itemId: string, body: AgentJournalItemBody, sequence: number) {
-    return { itemId, body, sequence, observedAt: sequence * 1000, revision: 1 }
-  }
-  function prompt(itemId: string, text: string, sequence: number) {
-    return journalItem(
-      itemId,
-      { kind: 'message', role: 'user', blocks: [{ type: 'text', text }] },
-      sequence
-    )
-  }
-
-  const patch = '@@ -1 +1 @@\n-before\n+after'
-  const OLDER = prompt('older', 'Oldest prompt', 1)
-  const LOADED: AgentJournalRenderItem[] = [
-    prompt('user', 'Edit it', 2),
-    journalItem(
-      'diff',
-      {
-        kind: 'diff',
-        path: 'src/a.ts',
-        patch: { head: patch, truncated: false, digest: 'fixture', byteLength: patch.length }
-      },
-      3
-    ),
-    prompt('user-2', 'Second prompt', 4),
-    prompt('user-3', 'Third prompt', 5),
-    ...Array.from({ length: 200 }, (_, index) =>
-      journalItem(
-        `tail-${index}`,
-        { kind: 'message', role: 'assistant', blocks: [{ type: 'text', text: `marker-${index}` }] },
-        index + 6
+  describe('revealing a diff while a rail jump pages', () => {
+    function journalItem(itemId: string, body: AgentJournalItemBody, sequence: number) {
+      return { itemId, body, sequence, observedAt: sequence * 1000, revision: 1 }
+    }
+    function prompt(itemId: string, text: string, sequence: number) {
+      return journalItem(
+        itemId,
+        { kind: 'message', role: 'user', blocks: [{ type: 'text', text }] },
+        sequence
       )
-    )
-  ]
+    }
 
-  function DiffTranscript({ holdPage }: { holdPage: () => Promise<void> }): React.JSX.Element {
-    const [loadedOlder, setLoadedOlder] = useState(false)
-    const items = useMemo(() => (loadedOlder ? [OLDER, ...LOADED] : LOADED), [loadedOlder])
-    const loadEarlier = useCallback(async (): Promise<NativeChatOlderPageResult> => {
-      await holdPage()
-      setLoadedOlder(true)
-      return 'applied'
-    }, [holdPage])
-    return (
-      <NativeChatMessageList
-        session={{
-          ...session(projectStructuredItemsToNativeChat(items)),
-          hasMore: !loadedOlder,
-          loadEarlier
-        }}
-        journalItems={items}
-        railOutline={loadedOlder ? [] : [{ id: 'older', text: 'Oldest prompt', hasImages: false }]}
-        isWorking={false}
-        expandSignal={false}
-      />
-    )
-  }
+    const patch = '@@ -1 +1 @@\n-before\n+after'
+    const OLDER = prompt('older', 'Oldest prompt', 1)
+    const LOADED: AgentJournalRenderItem[] = [
+      prompt('user', 'Edit it', 2),
+      journalItem(
+        'diff',
+        {
+          kind: 'diff',
+          path: 'src/a.ts',
+          patch: { head: patch, truncated: false, digest: 'fixture', byteLength: patch.length }
+        },
+        3
+      ),
+      ...Array.from({ length: 200 }, (_, index) =>
+        journalItem(
+          `tail-${index}`,
+          {
+            kind: 'message',
+            role: 'assistant',
+            blocks: [{ type: 'text', text: `marker-${index}` }]
+          },
+          index + 4
+        )
+      )
+    ]
 
-  it('keeps the diff in view when its page lands', async () => {
-    let release = (): void => {}
-    const holdPage = vi.fn(
-      () =>
-        new Promise<void>((resolve) => {
-          release = resolve
-        })
-    )
-    const scrollTo = vi.fn()
-    vi.spyOn(HTMLElement.prototype, 'scrollTo').mockImplementation(scrollTo)
-    const { container } = render(<DiffTranscript holdPage={holdPage} />)
+    function DiffTranscript({ holdPage }: { holdPage: () => Promise<void> }): React.JSX.Element {
+      const [loadedOlder, setLoadedOlder] = useState(false)
+      const items = useMemo(() => (loadedOlder ? [OLDER, ...LOADED] : LOADED), [loadedOlder])
+      const loadEarlier = useCallback(async (): Promise<NativeChatOlderPageResult> => {
+        await holdPage()
+        setLoadedOlder(true)
+        return 'applied'
+      }, [holdPage])
+      return (
+        <NativeChatMessageList
+          session={{
+            ...session(projectStructuredItemsToNativeChat(items)),
+            hasMore: !loadedOlder,
+            loadEarlier
+          }}
+          journalItems={items}
+          railOutline={
+            loadedOlder ? [] : [{ id: 'older', text: 'Oldest prompt', hasImages: false }]
+          }
+          isWorking={false}
+          expandSignal={false}
+        />
+      )
+    }
 
-    fireEvent.click(screen.getByRole('button', { name: 'Oldest prompt' }))
-    // Anti-vacuous: the older page is in flight.
-    expect(holdPage).toHaveBeenCalledTimes(1)
-    fireEvent.click(screen.getByRole('button', { name: /1 changed file/ }))
-    fireEvent.click(screen.getByRole('button', { name: /src\/a.ts/ }))
-    scrollTranscript(container, 6000)
-    expect(screen.getByText('Edited')).toBeInTheDocument()
-    scrollTo.mockClear()
+    function expectDiffInView(): void {
+      expect(
+        screen.getByRole('button', { name: /^Edited .*a\.ts(?:\s|$)/, expanded: true })
+      ).toBeInTheDocument()
+      const row = screen.getByText('Edited').closest<HTMLElement>('[data-index]')
+      if (!row) {
+        throw new Error('revealed diff has no mounted row')
+      }
+      const top = layout.aboveTranscriptPx + row.offsetTop - scroller().scrollTop
+      expect(row.offsetHeight).toBeGreaterThan(0)
+      expect(top).toBeGreaterThanOrEqual(-2)
+      expect(top).toBeLessThan(scroller().clientHeight - 2)
+    }
 
-    await act(async () => {
-      release()
-      await new Promise<void>((resolve) => setTimeout(resolve, 0))
+    it('keeps the diff in view when its page lands', async () => {
+      const pages = holdFirstPage()
+      render(<DiffTranscript holdPage={pages.holdPage} />)
+      await settle(10)
+      expect(distanceFromBottom()).toBe(0)
+      expect(screen.queryByText('Edited')).toBeNull()
+
+      await pickUnloadedWhilePaging('Oldest prompt')
+      expect(pages.asked()).toBe(1)
+      expect(screen.getByRole('button', { name: 'Oldest prompt' })).toHaveAttribute(
+        'aria-busy',
+        'true'
+      )
+
+      fireEvent.click(screen.getByRole('button', { name: /1 changed file/ }))
+      fireEvent.click(screen.getByRole('button', { name: /src\/a.ts/ }))
+      expect(screen.getByRole('button', { name: 'Oldest prompt' })).not.toHaveAttribute('aria-busy')
+      await settle(40)
+      expectDiffInView()
+
+      pages.release()
+      await settle(60)
+
+      expect(pages.asked()).toBe(1)
+      expect(screen.getByRole('button', { name: 'Oldest prompt' })).not.toHaveAttribute('aria-busy')
+      expectDiffInView()
     })
-
-    // The abandoned jump would have taken the pin and smooth-scrolled up to the oldest
-    // prompt; the prepend's own anchoring is an instant write.
-    expect(scrollTo.mock.calls.filter(([options]) => options?.behavior === 'smooth')).toEqual([])
-    expect(screen.getByText('Edited')).toBeInTheDocument()
   })
 })