fix: prune empty restored panes (#268)

Co-authored-by: wangqiong <wangqiong@yy.com>

src/client/state.ts

@@ -825,8 +825,9 @@ export function sanitizeState(parsed: unknown): SidebarState | undefined {
   // bottom tree.
   const seen = new Set<string>()
   const reid = new Map<string, string>()
-  const splits = sanitizeNode(record.splits, seen, reid)
-  if (splits === undefined) return undefined
+  const restoredSplits = sanitizeNode(record.splits, seen, reid)
+  if (restoredSplits === undefined) return undefined
+  const splits = pruneEmptyPanes(restoredSplits)
   // Bottom-panel fields arrived in a later build: a missing or malformed
   // value on an OLDER persisted state defaults (closed / default height /
   // empty pane) so existing layouts keep loading, like nextBrowser.
@@ -840,15 +841,23 @@ export function sanitizeState(parsed: unknown): SidebarState | undefined {
     ? record.bottomHeight
     : BOTTOM_DEFAULT
   const bottomHeight = Math.min(bottomCap, Math.max(BOTTOM_MIN, Math.round(rawHeight)))
-  const bottomSplits = sanitizeNode(record.bottomSplits, seen, reid)
-    ?? { kind: 'leaf' as const, id: uid('pane'), tabs: [], active: null }
+  const bottomSplits = pruneEmptyPanes(sanitizeNode(record.bottomSplits, seen, reid)
+    ?? { kind: 'leaf' as const, id: uid('pane'), tabs: [], active: null })
+  const requestedActivePane = typeof record.activePane === 'string'
+    ? (reid.get(record.activePane) ?? record.activePane)
+    : null
+  const activePane = requestedActivePane === null
+    ? null
+    : treeHasId(splits, requestedActivePane) || treeHasId(bottomSplits, requestedActivePane)
+      ? requestedActivePane
+      : firstLeaf(splits).id
   const maxWidth = typeof window !== 'undefined' ? window.innerWidth : Infinity
   return {
     panelOpen: record.panelOpen,
     width: Math.max(PANEL_MIN, Math.min(record.width, maxWidth)),
     // A stale duplicate pane id may have been re-ided; follow the rename so
     // new tabs still land in the pane the user was using.
-    activePane: typeof record.activePane === 'string' ? (reid.get(record.activePane) ?? record.activePane) : null,
+    activePane,
     nextTerminal: record.nextTerminal,
     nextBrowser,
     expanded: record.expanded as string[],
@@ -863,6 +872,16 @@ export function sanitizeState(parsed: unknown): SidebarState | undefined {
   }
 }
 
+/** Collapse persisted split panes left empty after ephemeral diff tabs are dropped. */
+function pruneEmptyPanes(node: SplitNode): SplitNode {
+  const leaves = allLeaves(node)
+  if (!leaves.some(leaf => leaf.tabs.length > 0)) return node
+  return leaves.reduce(
+    (tree, leaf) => leaf.tabs.length === 0 ? removeLeafAt(tree, leaf.id) : tree,
+    node,
+  )
+}
+
 /**
  * One tree node id, deduplicated against the ids already seen in this
  * state. Duplicates are exactly the pre-seeding counter-reset corruption

tests/state.spec.ts

@@ -188,6 +188,29 @@ describe('sidebar state', () => {
     expect((onlyDiff?.splits as { tabs: SidebarTab[] }).tabs).toEqual([])
   })
 
+  it('sanitize removes a pane emptied by ephemeral diff tabs', () => {
+    const valid = sanitizeState({
+      panelOpen: true,
+      width: 400,
+      nextTerminal: 1,
+      activePane: 'pane:diff',
+      expanded: [],
+      splits: {
+        kind: 'split',
+        id: 'split:1',
+        dir: 'col',
+        sizes: [0.5, 0.5],
+        children: [
+          { kind: 'leaf', id: 'pane:git', active: 'git', tabs: [{ id: 'git', type: 'git', title: 'Git' }] },
+          { kind: 'leaf', id: 'pane:diff', active: 'd1', tabs: [{ id: 'd1', type: 'diff', title: 'a.ts' }] },
+        ],
+      },
+    })
+    expect(valid?.splits.kind).toBe('leaf')
+    expect((valid?.splits as { id: string; tabs: SidebarTab[] }).id).toBe('pane:git')
+    expect(valid?.activePane).toBe('pane:git')
+  })
+
   it('dedupes the single-instance subagent tab (focuses instead of duplicating)', () => {
     let s = state()
     s = openTabInActivePane(s, { id: 'subagent', type: 'subagent', title: 'Subagents' })
@@ -716,11 +739,11 @@ describe('persisted state sanitization', () => {
     const clean = sanitizeState(corrupted)
     expect(clean).toBeDefined()
     const leaves = allLeaves(clean!.splits)
-    // The first occurrence keeps its id; the repeat gets a fresh unique one
-    // (exact suffix depends on the module-level uid counter, so assert shape).
-    expect(leaves[0]!.id).toBe('pane:1')
-    expect(new Set(leaves.map(leaf => leaf.id)).size).toBe(2)
-    expect(clean!.activePane).toBe(leaves[1]!.id)
+    // The empty first occurrence is pruned; the populated repeat keeps its
+    // fresh unique id and becomes active.
+    expect(leaves).toHaveLength(1)
+    expect(leaves[0]!.id).not.toBe('pane:1')
+    expect(clean!.activePane).toBe(leaves[0]!.id)
     // And an open must land in exactly one pane of the healed tree.
     const opened = openTabInActivePane(clean!, { id: 'editor:/a.ts', type: 'editor', title: 'a.ts', path: '/a.ts' })
     const owners = allLeaves(opened.splits).filter(leaf => leaf.tabs.some(tab => tab.path === '/a.ts'))