fix(test): avoid explicit any in mockImplementation typing

removeEmptyDirs() walks outDir with readdir() then stat()s each entry. If
another plugin (eg. vite-plugin-static-copy) writes into outDir around the
same build hook, a file can be renamed/removed between the two calls,
throwing ENOENT and failing the whole build intermittently.

Fixes wxt-dev/wxt#2533

packages/wxt/src/core/builders/vite/__tests__/remove-empty-dirs.test.ts

@@ -0,0 +1,72 @@
+import { mkdir, mkdtemp, rm, stat, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, beforeAll, describe, expect, it, vi } from "vitest";
+import { removeEmptyDirs } from "../index";
+
+// `stat` is mocked (defaulting to the real implementation) so individual
+// tests can override it to simulate a file disappearing mid-walk - the race
+// this suite exists to cover (oleks/mcp-chrome#61).
+vi.mock("node:fs/promises", async (importOriginal) => {
+	const actual = await importOriginal<typeof import("node:fs/promises")>();
+	return { ...actual, stat: vi.fn(actual.stat) };
+});
+
+const mockedStat = vi.mocked(stat);
+let realStat: typeof import("node:fs/promises").stat;
+
+describe("removeEmptyDirs", () => {
+	beforeAll(async () => {
+		realStat = (
+			await vi.importActual<typeof import("node:fs/promises")>(
+				"node:fs/promises",
+			)
+		).stat;
+	});
+
+	afterEach(() => {
+		mockedStat.mockImplementation(realStat);
+	});
+
+	it("removes nested empty directories", async () => {
+		const dir = await mkdtemp(join(tmpdir(), "wxt-remove-empty-dirs-"));
+		try {
+			await mkdir(join(dir, "a", "b"), { recursive: true });
+			await writeFile(join(dir, "a", "keep.txt"), "x");
+
+			await removeEmptyDirs(dir);
+
+			await expect(realStat(join(dir, "a", "b"))).rejects.toThrow();
+			await expect(realStat(join(dir, "a", "keep.txt"))).resolves.toBeDefined();
+		} finally {
+			await rm(dir, { recursive: true, force: true });
+		}
+	});
+
+	it("does not throw when a file disappears between readdir and stat (a concurrent plugin write, oleks/mcp-chrome#61)", async () => {
+		const dir = await mkdtemp(join(tmpdir(), "wxt-remove-empty-dirs-"));
+		try {
+			await mkdir(join(dir, "inject-scripts"), { recursive: true });
+			const raceyFile = join(dir, "inject-scripts", "recorder.js");
+			await writeFile(raceyFile, "x");
+
+			mockedStat.mockImplementation((async (
+				path: Parameters<typeof stat>[0],
+				...args: unknown[]
+			) => {
+				if (path === raceyFile) {
+					const err: NodeJS.ErrnoException = new Error(
+						"ENOENT: no such file or directory",
+					);
+					err.code = "ENOENT";
+					throw err;
+				}
+				return (realStat as (...a: unknown[]) => unknown)(path, ...args);
+			}) as typeof stat);
+
+			await expect(removeEmptyDirs(dir)).resolves.not.toThrow();
+		} finally {
+			await rm(dir, { recursive: true, force: true });
+		}
+	});
+});