fix(sidebar): stop bubbled dragleave events cancelling an in-progress drag

apps/sim/app/workspace/[workspaceId]/w/components/sidebar/hooks/use-drag-drop.test.tsx

@@ -9,6 +9,9 @@ vi.mock('next/navigation', () => ({
   useParams: () => ({ workspaceId: 'ws-1' }),
 }))
 
+/** Kept out of the module graph so this suite does not pull emcn's CSS modules through postcss. */
+vi.mock('@sim/emcn', () => ({ toast: { error: vi.fn() } }))
+
 vi.mock('@/hooks/queries/folders', () => ({
   useReorderFolders: () => ({ mutateAsync: vi.fn() }),
 }))
@@ -29,13 +32,23 @@ vi.mock('@/lib/folders/tree', () => ({
   getFolderPath: () => [],
 }))
 
-const { mockUseFolderStore } = vi.hoisted(() => {
-  const folderState = { setExpanded: () => {}, expandedFolders: new Set<string>() }
+const { mockUseFolderStore, mockSetExpanded, expandedFolders } = vi.hoisted(() => {
+  const expanded = new Set<string>()
+  const setExpanded = vi.fn((folderId: string, isExpanded: boolean) => {
+    if (isExpanded) expanded.add(folderId)
+    else expanded.delete(folderId)
+  })
+  const folderState = {
+    setExpanded,
+    expandedFolders: expanded,
+    clearSelection: () => {},
+    clearFolderSelection: () => {},
+  }
   const store = Object.assign(
     (selector: (state: typeof folderState) => unknown) => selector(folderState),
     { getState: () => folderState }
   )
-  return { mockUseFolderStore: store }
+  return { mockUseFolderStore: store, mockSetExpanded: setExpanded, expandedFolders: expanded }
 })
 vi.mock('@/stores/folders/store', () => ({ useFolderStore: mockUseFolderStore }))
 
@@ -63,6 +76,64 @@ function fakeDragOverEvent(): unknown {
   }
 }
 
+/**
+ * A `dragover` on a folder row. `clientY` sits in the middle band of the 100px rect, which is what
+ * `calculateFolderDropPosition` reads as "inside" — the position that arms the spring-open timer.
+ */
+function fakeFolderDragOverEvent(): unknown {
+  const currentTarget = {
+    getBoundingClientRect: () => ({ top: 0, bottom: 100, height: 100 }),
+  }
+  return {
+    preventDefault: () => {},
+    stopPropagation: () => {},
+    clientY: 50,
+    target: {},
+    currentTarget,
+  }
+}
+
+/** A `drop` carrying no selection payload: enough to record the destination, then bail. */
+function fakeDropEvent(): unknown {
+  return {
+    preventDefault: () => {},
+    stopPropagation: () => {},
+    dataTransfer: { getData: () => '' },
+  }
+}
+
+/**
+ * Registers a scroll container spanning x 0-200, then arms a drop indicator on it. Registration has
+ * to precede the first dragOver: the listener effect reads the container ref when `isDragging`
+ * flips, and `setScrollContainer` is a plain ref setter that triggers no re-render of its own.
+ */
+function armDragOverScrollContainer(): HTMLDivElement {
+  const scrollContainer = document.createElement('div')
+  scrollContainer.getBoundingClientRect = () =>
+    ({ left: 0, right: 200, top: 0, bottom: 400 }) as DOMRect
+  document.body.appendChild(scrollContainer)
+  act(() => {
+    latest.setScrollContainer(scrollContainer)
+  })
+  act(() => {
+    latest.createEdgeDropZone('workflow-1', 'before').onDragOver(fakeDragOverEvent() as never)
+  })
+  return scrollContainer
+}
+
+/** Chrome's `dragleave` shape: bubbles, and always reports a null `relatedTarget`. */
+function dispatchBubbledDragLeave(element: HTMLElement, clientX: number) {
+  act(() => {
+    const leave = new Event('dragleave', { bubbles: true }) as DragEvent
+    Object.defineProperties(leave, {
+      relatedTarget: { value: null },
+      clientX: { value: clientX },
+      clientY: { value: 200 },
+    })
+    element.dispatchEvent(leave)
+  })
+}
+
 let container: HTMLDivElement
 let root: Root
 
@@ -93,10 +164,10 @@ describe('useDragDrop stranded-drag reset', () => {
     container.remove()
     vi.unstubAllGlobals()
     vi.clearAllMocks()
+    expandedFolders.clear()
   })
 
   it('clears isDragging on a window dragend when no drop fired', () => {
-    // A drag entering the list flips isDragging on via initDragOver.
     act(() => {
       latest.createRootDropZone().onDragOver(fakeDragOverEvent() as never)
     })
@@ -109,16 +180,200 @@ describe('useDragDrop stranded-drag reset', () => {
     expect(latest.isDragging).toBe(false)
   })
 
+  /**
+   * `dragleave` bubbles and Chrome nulls its `relatedTarget`, so the container listener sees one
+   * for every descendant boundary the pointer crosses. Treating those as "left the list" wiped the
+   * drop indicator mid-drag, and `handleDrop` bails on a null indicator — so a release just after
+   * crossing a boundary did nothing at all. Nested rows in an expanded folder cross the most
+   * boundaries, which is why open folders looked like they broke dragging outright.
+   */
+  it('keeps the drop indicator when a bubbled dragleave has no relatedTarget but the pointer is still inside', () => {
+    const scrollContainer = armDragOverScrollContainer()
+    expect(latest.dropIndicator).toEqual({
+      targetId: 'workflow-1',
+      position: 'before',
+      folderId: null,
+    })
+
+    // A child row handing off to its sibling: pointer still well inside the list's 0-200 x-range.
+    dispatchBubbledDragLeave(scrollContainer, 100)
+
+    expect(latest.dropIndicator).not.toBeNull()
+    scrollContainer.remove()
+  })
+
+  /**
+   * The root drop zone's own `onDragLeave` clears the indicator through `isLeavingElement`, which
+   * made the same null-`relatedTarget` assumption. Fixing only the container listener would have
+   * left this second path clearing the indicator on every internal crossing.
+   */
+  it('keeps the drop indicator when the root drop zone sees a relatedTarget-less dragleave inside itself', () => {
+    const zone = document.createElement('div')
+    zone.getBoundingClientRect = () => ({ left: 0, right: 200, top: 0, bottom: 400 }) as DOMRect
+
+    act(() => {
+      latest.createEdgeDropZone('workflow-1', 'before').onDragOver(fakeDragOverEvent() as never)
+    })
+    expect(latest.dropIndicator).not.toBeNull()
+
+    act(() => {
+      latest.createRootDropZone().onDragLeave({
+        relatedTarget: null,
+        currentTarget: zone,
+        clientX: 100,
+        clientY: 200,
+      } as never)
+    })
+
+    expect(latest.dropIndicator).not.toBeNull()
+  })
+
+  it('clears the drop indicator when the pointer genuinely leaves the list', () => {
+    const scrollContainer = armDragOverScrollContainer()
+    expect(latest.dropIndicator).not.toBeNull()
+
+    dispatchBubbledDragLeave(scrollContainer, 900)
+
+    expect(latest.dropIndicator).toBeNull()
+    scrollContainer.remove()
+  })
+
   it('keeps isDragging active across dragOver updates until the drag ends', () => {
     act(() => {
       latest.createRootDropZone().onDragOver(fakeDragOverEvent() as never)
     })
     expect(latest.isDragging).toBe(true)
 
-    // A subsequent dragOver must not tear down the active drag.
     act(() => {
       latest.createRootDropZone().onDragOver(fakeDragOverEvent() as never)
     })
     expect(latest.isDragging).toBe(true)
   })
 })
+
+/**
+ * Hovering a collapsed folder mid-drag spring-opens it so you can drop inside. Every folder opened
+ * that way that the drop did NOT land in has to close again, or dragging past a folder silently
+ * leaves it open and the sidebar grows rows the user never asked to see.
+ */
+describe('useDragDrop spring-open revert', () => {
+  beforeEach(() => {
+    vi.useFakeTimers()
+    vi.stubGlobal(
+      'requestAnimationFrame',
+      () => 0 as unknown as ReturnType<typeof requestAnimationFrame>
+    )
+    vi.stubGlobal('cancelAnimationFrame', () => {})
+    container = document.createElement('div')
+    document.body.appendChild(container)
+    root = createRoot(container)
+    act(() => {
+      root.render(<Harness />)
+    })
+  })
+
+  afterEach(() => {
+    act(() => {
+      root.unmount()
+    })
+    container.remove()
+    vi.unstubAllGlobals()
+    vi.useRealTimers()
+    vi.clearAllMocks()
+    expandedFolders.clear()
+  })
+
+  /** Drives a drag that lingers over `folder-1` long enough to spring it open. */
+  function dragOverFolderUntilExpanded() {
+    act(() => {
+      latest.handleDragStart(null)
+    })
+    act(() => {
+      latest
+        .createFolderDragHandlers('folder-1', null)
+        .onDragOver(fakeFolderDragOverEvent() as never)
+    })
+    act(() => {
+      vi.advanceTimersByTime(500)
+    })
+  }
+
+  it('closes a folder it spring-opened when the drag ends without dropping into it', () => {
+    dragOverFolderUntilExpanded()
+    expect(mockSetExpanded).toHaveBeenCalledWith('folder-1', true)
+
+    // Esc-cancel / release outside: `dragend` fires with no drop recorded.
+    act(() => {
+      latest.handleDragEnd()
+    })
+
+    expect(mockSetExpanded).toHaveBeenCalledWith('folder-1', false)
+    expect(expandedFolders.has('folder-1')).toBe(false)
+  })
+
+  it('leaves a folder open when the drop landed inside it', () => {
+    dragOverFolderUntilExpanded()
+    mockSetExpanded.mockClear()
+
+    // `dragend` fires after every drop, so the revert path runs here too.
+    act(() => {
+      void latest.createFolderDragHandlers('folder-1', null).onDrop(fakeDropEvent() as never)
+    })
+    act(() => {
+      latest.handleDragEnd()
+    })
+
+    expect(mockSetExpanded).not.toHaveBeenCalledWith('folder-1', false)
+    expect(expandedFolders.has('folder-1')).toBe(true)
+  })
+
+  /**
+   * The spring-open timer is armed for 400ms, so a drag ending just before it fires leaves it
+   * pending. Relying on the effect cleanup to cancel it would let it land after the drag-end
+   * collapse had already emptied the set — re-adding the folder for the *next* drag to close, by
+   * which point the user had opened it themselves.
+   */
+  it('does not spring-open a folder when the drag ends before the timer fires', () => {
+    act(() => {
+      latest.handleDragStart(null)
+    })
+    act(() => {
+      latest
+        .createFolderDragHandlers('folder-1', null)
+        .onDragOver(fakeFolderDragOverEvent() as never)
+    })
+
+    /**
+     * Deliberately outside `act`: the race only exists while React has scheduled the drag-end state
+     * changes but not yet committed them, so the effect cleanup has not run and the timer is still
+     * armed. Wrapping this in `act` would flush the commit first and cancel the timer via the
+     * cleanup, hiding the very gap under test.
+     */
+    latest.handleDragEnd()
+    act(() => {
+      vi.advanceTimersByTime(500)
+    })
+
+    expect(mockSetExpanded).not.toHaveBeenCalledWith('folder-1', true)
+    expect(expandedFolders.has('folder-1')).toBe(false)
+
+    // Nothing was left behind for a later drag to collapse.
+    act(() => {
+      latest.handleDragEnd()
+    })
+    expect(mockSetExpanded).not.toHaveBeenCalledWith('folder-1', false)
+  })
+
+  it('never closes a folder the user had already opened themselves', () => {
+    expandedFolders.add('folder-1')
+
+    dragOverFolderUntilExpanded()
+    act(() => {
+      latest.handleDragEnd()
+    })
+
+    // Already-expanded folders are skipped by the spring-open effect, so nothing to revert.
+    expect(mockSetExpanded).not.toHaveBeenCalledWith('folder-1', false)
+    expect(expandedFolders.has('folder-1')).toBe(true)
+  })
+})