fix(worker): keep the alarm when an object is exported again

src/worker.ts

@@ -228,6 +228,11 @@ class MigratorState {
 		}
 	}
 
+	/** The alarm time saved when the object was marked migrated, until a rollback restores it. */
+	get savedAlarm(): number | null {
+		return this.#savedAlarm;
+	}
+
 	get name(): string | null {
 		return this.#savedName ?? this.ctx.id.name ?? null;
 	}
@@ -238,6 +243,7 @@ class MigratorState {
 		this.sql!.exec(`INSERT OR REPLACE INTO "${STATE_TABLE}"(key, value) VALUES ('state', 'migrated')`);
 		if (alarm !== null) {
 			this.sql!.exec(`INSERT OR REPLACE INTO "${STATE_TABLE}"(key, value) VALUES ('alarm', ?)`, alarm);
+			this.#savedAlarm = alarm;
 		}
 		this.#migrated = true;
 	}
@@ -381,7 +387,9 @@ async function exportPage(
 		return { statements: out, cursor: encodeCursor(cursor) };
 	}
 
-	const alarm = await m.ctx.storage.getAlarm();
+	// A migrated object's alarm was removed and saved, so a second export
+	// (for example after the destination failed) still reports it.
+	const alarm = (await m.ctx.storage.getAlarm()) ?? m.savedAlarm;
 	const finalCursor = cursor;
 	m.ctx.storage.transactionSync(() => {
 		for (const s of tailStatements(sql, tables, m, alarm)) push(s);

tests/export.test.ts

@@ -146,6 +146,20 @@ describe("after migration", () => {
 		const again = await exportInto("moved");
 		expect(again.db.prepare(`SELECT count(*) AS n FROM notes`).get()).toEqual({ n: 3 });
 	});
+
+	test("an object exported a second time still carries its alarm", async () => {
+		await seed(worker, "alarm-twice");
+		const { alarm } = await sourceSnapshot(worker, "alarm-twice");
+		expect(alarm).not.toBeNull();
+
+		const alarmIn = async () => {
+			const { db } = await exportInto("alarm-twice");
+			return (db.prepare(`SELECT value FROM __do_meta WHERE key = 'alarm'`).get() as { value: number | null }).value;
+		};
+		// For example, the destination failed after the last page and migrate runs again.
+		expect(await alarmIn()).toBe(alarm);
+		expect(await alarmIn()).toBe(alarm);
+	});
 });
 
 describe("auth", () => {

tests/smoke/run.ts

@@ -66,6 +66,14 @@ await check("resolve by id returns the name the Durable Object saved", async ()
 	assert.equal(resolved.name, name);
 });
 
+await check("a migrated Durable Object exported again still reports its alarm", async () => {
+	const db = new DatabaseSync(":memory:", { enableForeignKeyConstraints: false });
+	for await (const page of migrator.exportObject({ binding: "ROOMS", id })) db.exec(page.sql);
+	const alarm = db.prepare(`SELECT value FROM __do_meta WHERE key = 'alarm'`).get() as { value: unknown };
+	// The fixture's seed schedules its alarm for 2099-01-01.
+	assert.equal(alarm.value, Date.UTC(2099, 0, 1));
+});
+
 await check("a KV write during the export makes it fail", async () => {
 	const dirty = `${run}-dirty`;
 	assert.equal((await app(dirty, "seed?big=1")).status, 200);