fix(explorer): apply directory toggles atomically

packages/app/src/components/file-explorer-pane.tsx

@@ -42,6 +42,7 @@ import {
   flattenExplorerTree,
   reconcileRestoredExpandedPaths,
   restoreExpandedDirectories,
+  setExpandedDirectoryPath,
   showHiddenFilesAndRestoreExpandedDirectories,
   type ExplorerTreeRow,
 } from "@/file-explorer/tree";
@@ -755,15 +756,14 @@ function toggleDirectory({
     return;
   }
   const isExpanded = expandedPaths.has(entry.path);
-  if (isExpanded) {
-    setExpandedPathsForWorkspace(
-      workspaceStateKey,
-      Array.from(expandedPaths).filter((path) => path !== entry.path),
-    );
-    return;
-  }
-  setExpandedPathsForWorkspace(workspaceStateKey, [...Array.from(expandedPaths), entry.path]);
-  if (!directories.has(entry.path)) {
+  setExpandedPathsForWorkspace(workspaceStateKey, (currentPaths) =>
+    setExpandedDirectoryPath({
+      currentExpandedPaths: currentPaths,
+      directoryPath: entry.path,
+      expanded: !isExpanded,
+    }),
+  );
+  if (!isExpanded && !directories.has(entry.path)) {
     void requestDirectoryListing(entry.path, {
       recordHistory: false,
       setCurrentPath: false,

packages/app/src/file-explorer/tree.test.ts

@@ -5,6 +5,7 @@ import {
   flattenExplorerTree,
   reconcileRestoredExpandedPaths,
   restoreExpandedDirectories,
+  setExpandedDirectoryPath,
   showHiddenFilesAndRestoreExpandedDirectories,
 } from "./tree";
 
@@ -153,6 +154,22 @@ describe("file explorer tree", () => {
     expect(paths).toEqual([".", "manual"]);
   });
 
+  it("applies a directory click to the latest restored expansion paths", () => {
+    const expanded = setExpandedDirectoryPath({
+      currentExpandedPaths: [".", "restored"],
+      directoryPath: "manual",
+      expanded: true,
+    });
+    const collapsed = setExpandedDirectoryPath({
+      currentExpandedPaths: expanded,
+      directoryPath: "manual",
+      expanded: false,
+    });
+
+    expect(expanded).toEqual([".", "restored", "manual"]);
+    expect(collapsed).toEqual([".", "restored"]);
+  });
+
   it("shows hidden files before waiting for expanded directories to restore", async () => {
     const rootDirectory = {
       path: ".",

packages/app/src/file-explorer/tree.ts

@@ -36,6 +36,12 @@ interface ReconcileRestoredExpandedPathsInput {
   restoredExpandedPaths: string[];
 }
 
+interface SetExpandedDirectoryPathInput {
+  currentExpandedPaths: readonly string[];
+  directoryPath: string;
+  expanded: boolean;
+}
+
 export function flattenExplorerTree({
   directories,
   expandedPaths,
@@ -153,6 +159,20 @@ export function reconcileRestoredExpandedPaths({
   return Array.from(reconciledPaths);
 }
 
+export function setExpandedDirectoryPath({
+  currentExpandedPaths,
+  directoryPath,
+  expanded,
+}: SetExpandedDirectoryPathInput): string[] {
+  const nextPaths = new Set(currentExpandedPaths);
+  if (expanded) {
+    nextPaths.add(directoryPath);
+  } else {
+    nextPaths.delete(directoryPath);
+  }
+  return Array.from(nextPaths);
+}
+
 function rowsForDirectory(
   directory: ExplorerDirectory,
   depth: number,