cron: recover missing split config file

src/cron/store.test.ts

@@ -238,6 +238,40 @@ describe("cron store", () => {
     expect(stateFile.jobs["job-1"].state.nextRunAtMs).toBe(payload.jobs[0].createdAtMs + 60_000);
   });
 
+  it("recreates a missing config file without rewriting unchanged state", async () => {
+    const store = await makeStorePath();
+    const statePath = store.storePath.replace(/\.json$/, "-state.json");
+    const payload = makeStore("job-1", true);
+    payload.jobs[0].state = { nextRunAtMs: payload.jobs[0].createdAtMs + 60_000 };
+
+    await saveCronStore(store.storePath, payload);
+    await loadCronStore(store.storePath);
+    const stateRawBefore = await fs.readFile(statePath, "utf-8");
+    await fs.rm(store.storePath);
+
+    const renamedDestinations: string[] = [];
+    const origRename = fs.rename.bind(fs);
+    const spy = vi.spyOn(fs, "rename").mockImplementation(async (src, dest) => {
+      renamedDestinations.push(String(dest));
+      return origRename(src, dest);
+    });
+
+    try {
+      await saveCronStore(store.storePath, payload);
+    } finally {
+      spy.mockRestore();
+    }
+
+    const config = JSON.parse(await fs.readFile(store.storePath, "utf-8"));
+    const stateRawAfter = await fs.readFile(statePath, "utf-8");
+
+    expect(config.jobs[0].id).toBe("job-1");
+    expect(config.jobs[0].state).toEqual({});
+    expect(stateRawAfter).toBe(stateRawBefore);
+    expect(renamedDestinations).toContain(store.storePath);
+    expect(renamedDestinations).not.toContain(statePath);
+  });
+
   it("migrates legacy inline state into the state sidecar", async () => {
     const store = await makeStorePath();
     const statePath = store.storePath.replace(/\.json$/, "-state.json");

src/cron/store.ts

@@ -232,6 +232,25 @@ async function atomicWrite(filePath: string, content: string, dirMode = 0o700):
   await setSecureFileMode(filePath);
 }
 
+async function serializedFileNeedsWrite(
+  filePath: string,
+  expectedJson: string,
+  contentChanged: boolean,
+): Promise<boolean> {
+  if (contentChanged) {
+    return true;
+  }
+  try {
+    const diskJson = await fs.promises.readFile(filePath, "utf-8");
+    return diskJson !== expectedJson;
+  } catch (err) {
+    if ((err as { code?: unknown })?.code === "ENOENT") {
+      return true;
+    }
+    throw err;
+  }
+}
+
 export async function saveCronStore(
   storePath: string,
   store: CronStoreFile,
@@ -247,22 +266,10 @@ export async function saveCronStore(
   const configChanged = cache?.configJson !== configJson;
   const stateChanged = cache?.stateJson !== stateJson;
   const migrating = cache?.needsSplitMigration === true;
-  let stateNeedsWrite = stateChanged;
+  const configNeedsWrite = await serializedFileNeedsWrite(storePath, configJson, configChanged);
+  const stateNeedsWrite = await serializedFileNeedsWrite(statePath, stateJson, stateChanged);
 
-  if (!stateNeedsWrite) {
-    try {
-      const diskStateJson = await fs.promises.readFile(statePath, "utf-8");
-      stateNeedsWrite = diskStateJson !== stateJson;
-    } catch (err) {
-      if ((err as { code?: unknown })?.code === "ENOENT") {
-        stateNeedsWrite = true;
-      } else {
-        throw err;
-      }
-    }
-  }
-
-  if (!configChanged && !stateNeedsWrite && !migrating) {
+  if (!configNeedsWrite && !stateNeedsWrite && !migrating) {
     return;
   }
 
@@ -274,7 +281,7 @@ export async function saveCronStore(
     updatedCache.stateJson = stateJson;
   }
 
-  if (configChanged || migrating) {
+  if (configNeedsWrite || migrating) {
     // Determine backup need: only when config actually changed (not migration-only).
     const skipBackup = opts?.skipBackup === true || !configChanged;
     if (!skipBackup) {