fix(desktop): stop a folder rename from throwing out of the Files tab fs handler

apps/desktop/src/renderer/routes/_authenticated/_dashboard/v2-workspace/$workspaceId/components/WorkspaceSidebar/components/FilesTab/hooks/useFilesTabBridge/useFilesTabBridge.ts

@@ -10,6 +10,7 @@ import type { TreeBookkeeping } from "../../utils/treeBookkeeping";
 import { purgeDirectory, rekeyDirectory } from "../../utils/treeBookkeeping";
 import {
 	asDirectoryHandle,
+	lookupDirectory,
 	resolveDeleteTreePath,
 	stripTrailingSlash,
 	toAbs,
@@ -484,8 +485,9 @@ export function useFilesTabBridge({
 					if (!loadedDirsRef.current.has(newDir)) {
 						unloadedDirCandidatesRef.current.add(newDir);
 					}
-					const handle = asDirectoryHandle(model.getItem(newKey));
-					if (handle?.isExpanded()) void fetchDir(newDir);
+					if (lookupDirectory(model, newKey)?.isExpanded()) {
+						void fetchDir(newDir);
+					}
 				}
 				return;
 			}

apps/desktop/src/renderer/routes/_authenticated/_dashboard/v2-workspace/$workspaceId/components/WorkspaceSidebar/components/FilesTab/utils/treePath/index.ts

@@ -1,6 +1,7 @@
 export {
 	asDirectoryHandle,
 	basename,
+	lookupDirectory,
 	parentRel,
 	resolveDeleteTreePath,
 	stripTrailingSlash,

apps/desktop/src/renderer/routes/_authenticated/_dashboard/v2-workspace/$workspaceId/components/WorkspaceSidebar/components/FilesTab/utils/treePath/treePath.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it } from "bun:test";
-import { resolveDeleteTreePath } from "./treePath";
+import { FileTree } from "@pierre/trees";
+import { lookupDirectory, resolveDeleteTreePath } from "./treePath";
 
 describe("resolveDeleteTreePath", () => {
 	it("infers a tracked directory when watcher metadata is absent", () => {
@@ -33,3 +34,32 @@ describe("resolveDeleteTreePath", () => {
 		});
 	});
 });
+
+describe("lookupDirectory", () => {
+	// The watcher stats a path to decide `isDirectory` and reports false when
+	// the stat loses a race with the rename that produced the event, so a
+	// directory can enter the tree as a file. Every later lookup beneath it
+	// then walks into a node that has no child index.
+	const treeHoldingBuildAsAFile = () => {
+		const model = new FileTree({ paths: ["src/out/keep.ts"] });
+		model.add("build");
+		return model;
+	};
+
+	it("yields no handle for a path the model cannot resolve", () => {
+		const model = treeHoldingBuildAsAFile();
+		expect(() => model.getItem("build/out/")).toThrow();
+		expect(lookupDirectory(model, "build/out/")).toBeNull();
+	});
+
+	it("still reports an expanded directory the model does hold", () => {
+		const model = treeHoldingBuildAsAFile();
+		lookupDirectory(model, "src/out/")?.expand();
+		expect(lookupDirectory(model, "src/out/")?.isExpanded()).toBe(true);
+	});
+
+	it("yields no handle for a file", () => {
+		const model = treeHoldingBuildAsAFile();
+		expect(lookupDirectory(model, "src/out/keep.ts")).toBeNull();
+	});
+});

apps/desktop/src/renderer/routes/_authenticated/_dashboard/v2-workspace/$workspaceId/components/WorkspaceSidebar/components/FilesTab/utils/treePath/treePath.ts

@@ -1,4 +1,5 @@
 import type {
+	FileTree,
 	FileTreeDirectoryHandle,
 	FileTreeItemHandle,
 } from "@pierre/trees";
@@ -62,3 +63,25 @@ export function asDirectoryHandle(
 ): FileTreeDirectoryHandle | null {
 	return handle?.isDirectory() ? (handle as FileTreeDirectoryHandle) : null;
 }
+
+/**
+ * The directory handle for `treePath`, or null when Pierre can't produce one.
+ *
+ * `getItem` is typed to return null for a path Pierre doesn't hold, but it
+ * throws instead when the lookup walks through a node with no child index —
+ * a path whose ancestor Pierre holds as a file. That happens when the watcher
+ * loses a stat race and reports a directory with `isDirectory: false`, so the
+ * fs-event handler adds it as a file and every later lookup beneath it throws.
+ * Callers use the handle only to ask whether a directory is already expanded,
+ * and not being able to ask is the same answer as "not expanded".
+ */
+export function lookupDirectory(
+	model: Pick<FileTree, "getItem">,
+	treePath: string,
+): FileTreeDirectoryHandle | null {
+	try {
+		return asDirectoryHandle(model.getItem(treePath));
+	} catch {
+		return null;
+	}
+}