feat(FN-4938): complete Step 2 — add helper and wire cleanup

Fusion-Task-Id: FN-4938
Fusion-Task-Lineage: 8b53a5da-1321-4796-9775-ff043efdcef3

packages/engine/src/__tests__/worktree-desktop-artifacts.test.ts

@@ -0,0 +1,90 @@
+import { mkdtempSync, mkdirSync, existsSync } from "node:fs";
+import * as fsPromises from "node:fs/promises";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import { afterEach, describe, expect, it, vi } from "vitest";
+vi.mock("node:fs/promises", async () => {
+  const actual = await vi.importActual<typeof import("node:fs/promises")>("node:fs/promises");
+  return {
+    ...actual,
+    rm: vi.fn(actual.rm),
+  };
+});
+
+import {
+  DESKTOP_ARTIFACT_RELATIVE_PATHS,
+  removeDesktopBuildArtifacts,
+} from "../worktree-desktop-artifacts.js";
+
+describe("removeDesktopBuildArtifacts", () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("removes both desktop artifact directories when both exist", async () => {
+    const root = mkdtempSync(join(tmpdir(), "wt-artifacts-"));
+    for (const path of DESKTOP_ARTIFACT_RELATIVE_PATHS) {
+      mkdirSync(join(root, path), { recursive: true });
+    }
+
+    const result = await removeDesktopBuildArtifacts(root);
+
+    expect(result.removed.sort()).toEqual([...DESKTOP_ARTIFACT_RELATIVE_PATHS].sort());
+    expect(result.skipped).toEqual([]);
+    expect(result.failures).toEqual([]);
+    for (const path of DESKTOP_ARTIFACT_RELATIVE_PATHS) {
+      expect(existsSync(join(root, path))).toBe(false);
+    }
+  });
+
+  it("removes only existing dist-electron path and marks dist as skipped", async () => {
+    const root = mkdtempSync(join(tmpdir(), "wt-artifacts-"));
+    mkdirSync(join(root, "packages/desktop/dist-electron"), { recursive: true });
+
+    const result = await removeDesktopBuildArtifacts(root);
+
+    expect(result.removed).toEqual(["packages/desktop/dist-electron"]);
+    expect(result.skipped).toEqual(["packages/desktop/dist"]);
+    expect(result.failures).toEqual([]);
+    expect(existsSync(join(root, "packages/desktop/dist-electron"))).toBe(false);
+  });
+
+  it("is a no-op when neither path exists", async () => {
+    const root = mkdtempSync(join(tmpdir(), "wt-artifacts-"));
+
+    const result = await removeDesktopBuildArtifacts(root);
+
+    expect(result.removed).toEqual([]);
+    expect(result.skipped.sort()).toEqual([...DESKTOP_ARTIFACT_RELATIVE_PATHS].sort());
+    expect(result.failures).toEqual([]);
+  });
+
+  it("captures per-path failure and continues", async () => {
+    const root = mkdtempSync(join(tmpdir(), "wt-artifacts-"));
+    for (const path of DESKTOP_ARTIFACT_RELATIVE_PATHS) {
+      mkdirSync(join(root, path), { recursive: true });
+    }
+    const rmSpy = vi.mocked(fsPromises.rm).mockImplementation(async (pathLike: fsPromises.PathLike) => {
+      if (String(pathLike).endsWith("packages/desktop/dist")) {
+        throw new Error("boom");
+      }
+    });
+
+    const warn = vi.fn();
+    const result = await removeDesktopBuildArtifacts(root, { log: vi.fn(), warn });
+
+    expect(rmSpy).toHaveBeenCalled();
+    expect(result.removed).toEqual(["packages/desktop/dist-electron"]);
+    expect(result.failures).toEqual([{ path: "packages/desktop/dist", error: "boom" }]);
+    expect(warn).toHaveBeenCalledWith(expect.stringContaining("Failed to remove desktop build artifact directory packages/desktop/dist: boom"));
+  });
+
+  it("returns early when worktreePath is falsy", async () => {
+    const warn = vi.fn();
+
+    const result = await removeDesktopBuildArtifacts("", { log: vi.fn(), warn });
+
+    expect(result).toEqual({ removed: [], skipped: [], failures: [] });
+    expect(warn).toHaveBeenCalledWith("Desktop artifact cleanup skipped: missing worktree path");
+  });
+});