perf(plugins): cache runtime mirror file decisions

src/plugin-sdk/file-lock.test.ts

@@ -1,7 +1,7 @@
 import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
-import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import {
   acquireFileLock,
   drainFileLockStateForTest,
@@ -55,4 +55,28 @@ describe("acquireFileLock", () => {
       return true;
     });
   }, 5_000);
+
+  it("closes an opened lock handle when writing the owner payload fails", async () => {
+    const filePath = path.join(tempDir, "write-fails");
+    const writeError = new Error("owner write failed");
+    const close = vi.fn().mockResolvedValue(undefined);
+    vi.spyOn(fs, "open").mockResolvedValue({
+      close,
+      writeFile: vi.fn().mockRejectedValue(writeError),
+    } as unknown as Awaited<ReturnType<typeof fs.open>>);
+
+    await expect(
+      acquireFileLock(filePath, {
+        retries: {
+          retries: 0,
+          factor: 1,
+          minTimeout: 1,
+          maxTimeout: 1,
+        },
+        stale: 100,
+      }),
+    ).rejects.toThrow(writeError);
+
+    expect(close).toHaveBeenCalledTimes(1);
+  });
 });

src/plugin-sdk/file-lock.ts

@@ -183,10 +183,16 @@ export async function acquireFileLock(
   for (let attempt = 0; attempt <= options.retries.retries; attempt += 1) {
     try {
       const handle = await fs.open(lockPath, "wx");
-      await handle.writeFile(
-        JSON.stringify({ pid: process.pid, createdAt: new Date().toISOString() }, null, 2),
-        "utf8",
-      );
+      try {
+        await handle.writeFile(
+          JSON.stringify({ pid: process.pid, createdAt: new Date().toISOString() }, null, 2),
+          "utf8",
+        );
+      } catch (writeError) {
+        await handle.close().catch(() => undefined);
+        await fs.rm(lockPath, { force: true }).catch(() => undefined);
+        throw writeError;
+      }
       HELD_LOCKS.set(normalizedFile, { count: 1, handle, lockPath });
       return {
         lockPath,