feat(project-view): restore the persisted expansion state as the user left it (#782)

The Project view restored only expanded paths inside the project roots and always re-expanded the roots. Restore the persisted state as is (a collapsed root stays collapsed, nodes outside it such as content roots stay open); only a first open expands the roots.

Co-authored-by: ntbang0901 <[email protected]>

src/features/project-tree/store.test.ts

@@ -68,6 +68,14 @@ describe("lazy loading", () => {
     expect([...useProjectTree.getState().expanded].sort()).toEqual(["/p", "/p/docs"]);
   });
 
+  it("keeps a collapsed project root collapsed and an expanded node outside it open", async () => {
+    setExpanded(new Set(["/other/lib"]));
+    await new Promise((r) => setTimeout(r, 350));
+    initProjectTree(null);
+    initProjectTree(ROOT, "proj");
+    expect([...useProjectTree.getState().expanded]).toEqual(["/other/lib"]);
+  });
+
   it("drops a folder that vanished and collapses it", async () => {
     await loadDir(ROOT);
     setExpanded(new Set([ROOT, "/p/gone"]));

src/features/project-tree/store.ts

@@ -301,11 +301,12 @@ function initialExpanded(root: string | null, mode: ViewMode, members = get().me
         r.scope === "scratches" && r.path ? [r.path] : [],
       ),
     );
-  const persisted = mode === "project" ? (readJson<string[]>(expandedKey(root)) ?? []) : [];
-  const roots = members ?? [root];
-  const expanded = new Set(persisted.filter((p) => roots.some((r) => isSameOrInside(p, r))));
-  roots.forEach((r) => expanded.add(r));
-  return expanded;
+  // The tree as the user left it, like IDEA: a collapsed project root stays collapsed, and
+  // nodes outside it (content roots, contributed roots) stay open.
+  // Keys of nodes that no longer exist are inert. Only a first open expands the roots.
+  const persisted = mode === "project" ? readJson<string[]>(expandedKey(root)) : null;
+  if (persisted) return new Set(persisted);
+  return new Set(members ?? [root]);
 }
 
 function persistExpanded() {