fix: harden retained log streaming

packages/api/src/router/test/log.spec.ts

@@ -0,0 +1,79 @@
+import { describe, expect, test, vi } from "vitest";
+
+import type { Session } from "@homarr/auth";
+import type { LoggerMessage } from "@homarr/redis";
+
+import { logRouter } from "../log";
+
+const mocks = vi.hoisted(() => ({
+  getRecentAsync: vi.fn(),
+  subscribeAsync: vi.fn(),
+}));
+
+vi.mock("@homarr/redis", () => ({
+  loggingChannel: {
+    getRecentAsync: mocks.getRecentAsync,
+    subscribeAsync: mocks.subscribeAsync,
+  },
+}));
+
+const session = {
+  user: {
+    id: "log-viewer",
+    permissions: ["other-view-logs"],
+    colorScheme: "light",
+  },
+  expires: new Date(0).toISOString(),
+} satisfies Session;
+
+const createMessage = (id: string, timestamp: number): LoggerMessage => ({
+  id,
+  timestamp: new Date(timestamp),
+  level: "info",
+  message: id,
+});
+
+describe("log.subscribe", () => {
+  test("emits history before buffered live messages without duplicates", async () => {
+    const historyDeferred = Promise.withResolvers<LoggerMessage[]>();
+    let onMessage: ((message: LoggerMessage) => void) | undefined;
+    const unsubscribe = vi.fn();
+
+    mocks.subscribeAsync.mockImplementation(async (callback: (message: LoggerMessage) => void) => {
+      onMessage = callback;
+      return unsubscribe;
+    });
+    mocks.getRecentAsync.mockReturnValue(historyDeferred.promise);
+
+    const caller = logRouter.createCaller({
+      db: null as never,
+      deviceType: undefined,
+      session,
+    });
+    const subscription = await caller.subscribe({ levels: ["info"] });
+    const events: object[] = [];
+    const observer = subscription.subscribe({
+      next(event) {
+        events.push(event);
+      },
+    });
+
+    await vi.waitFor(() => expect(mocks.getRecentAsync).toHaveBeenCalledOnce());
+
+    const retainedMessage = createMessage("retained", 1);
+    const liveMessage = createMessage("live", 2);
+    onMessage?.(retainedMessage);
+    onMessage?.(liveMessage);
+    historyDeferred.resolve([retainedMessage]);
+
+    await vi.waitFor(() =>
+      expect(events).toEqual([
+        { type: "history", messages: [retainedMessage] },
+        { type: "message", message: liveMessage },
+      ]),
+    );
+
+    observer.unsubscribe();
+    expect(unsubscribe).toHaveBeenCalledOnce();
+  });
+});