refactor: unify monitor abort lifecycle handling

src/infra/abort-signal.test.ts

@@ -0,0 +1,29 @@
+import { describe, expect, it } from "vitest";
+import { waitForAbortSignal } from "./abort-signal.js";
+
+describe("waitForAbortSignal", () => {
+  it("resolves immediately when signal is missing", async () => {
+    await expect(waitForAbortSignal(undefined)).resolves.toBeUndefined();
+  });
+
+  it("resolves immediately when signal is already aborted", async () => {
+    const abort = new AbortController();
+    abort.abort();
+    await expect(waitForAbortSignal(abort.signal)).resolves.toBeUndefined();
+  });
+
+  it("waits until abort fires", async () => {
+    const abort = new AbortController();
+    let resolved = false;
+
+    const task = waitForAbortSignal(abort.signal).then(() => {
+      resolved = true;
+    });
+    await Promise.resolve();
+    expect(resolved).toBe(false);
+
+    abort.abort();
+    await task;
+    expect(resolved).toBe(true);
+  });
+});

src/infra/abort-signal.ts

@@ -0,0 +1,12 @@
+export async function waitForAbortSignal(signal?: AbortSignal): Promise<void> {
+  if (!signal || signal.aborted) {
+    return;
+  }
+  await new Promise<void>((resolve) => {
+    const onAbort = () => {
+      signal.removeEventListener("abort", onAbort);
+      resolve();
+    };
+    signal.addEventListener("abort", onAbort, { once: true });
+  });
+}