perf: deduplicate concurrent API reads

src/auth/api-client.test.ts

@@ -0,0 +1,61 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  _clearApiClientInflightForTests,
+  fetchJson,
+  setTokenGetter,
+} from './api-client.js';
+
+function jsonResponse(body: unknown): Response {
+  return new Response(JSON.stringify(body), {
+    status: 200,
+    headers: { 'content-type': 'application/json' },
+  });
+}
+
+test('deduplicates concurrent GET requests for the same URL and token', async () => {
+  const originalFetch = globalThis.fetch;
+  let calls = 0;
+  let resolveFetch: ((response: Response) => void) | undefined;
+  globalThis.fetch = ((_: string | URL | Request, init?: RequestInit) => {
+    calls += 1;
+    assert.equal(new Headers(init?.headers).get('authorization'), 'Bearer test-token');
+    return new Promise<Response>(resolve => { resolveFetch = resolve; });
+  }) as typeof fetch;
+  setTokenGetter(() => 'test-token');
+  _clearApiClientInflightForTests();
+
+  try {
+    const first = fetchJson<{ value: number }>('/api/test');
+    const second = fetchJson<{ value: number }>('/api/test');
+    assert.equal(calls, 1);
+    resolveFetch?.(jsonResponse({ value: 42 }));
+    assert.deepEqual(await first, { value: 42 });
+    assert.deepEqual(await second, { value: 42 });
+  } finally {
+    globalThis.fetch = originalFetch;
+    setTokenGetter(() => null);
+    _clearApiClientInflightForTests();
+  }
+});
+
+test('does not retain a failed GET request', async () => {
+  const originalFetch = globalThis.fetch;
+  let calls = 0;
+  globalThis.fetch = (async () => {
+    calls += 1;
+    if (calls === 1) throw new Error('network down');
+    return jsonResponse({ ok: true });
+  }) as typeof fetch;
+  setTokenGetter(() => null);
+  _clearApiClientInflightForTests();
+
+  try {
+    await assert.rejects(fetchJson('/api/retry'), /network down/);
+    assert.deepEqual(await fetchJson('/api/retry'), { ok: true });
+    assert.equal(calls, 2);
+  } finally {
+    globalThis.fetch = originalFetch;
+    _clearApiClientInflightForTests();
+  }
+});

src/auth/api-client.ts

@@ -1,13 +1,13 @@
 /** 全局认证 fetch 客户端 */
 
 let tokenGetter: () => string | null = () => null;
+const inflightGetRequests = new Map<string, Promise<unknown>>();
 
 export function setTokenGetter(fn: () => string | null) {
   tokenGetter = fn;
 }
 
-export async function fetchJson<T>(url: string, options?: RequestInit): Promise<T> {
-  const token = tokenGetter();
+async function executeJsonRequest<T>(url: string, options: RequestInit | undefined, token: string | null): Promise<T> {
   const res = await fetch(url, {
     ...options,
     headers: {
@@ -22,3 +22,25 @@ export async function fetchJson<T>(url: string, options?: RequestInit): Promise<
   if (!res.ok) throw new Error(`API error: ${res.status} ${res.statusText}`);
   return res.json();
 }
+
+export async function fetchJson<T>(url: string, options?: RequestInit): Promise<T> {
+  const token = tokenGetter();
+  const method = (options?.method || 'GET').toUpperCase();
+  const canDedupe = method === 'GET' && options?.body == null && options?.signal == null;
+  if (!canDedupe) return executeJsonRequest<T>(url, options, token);
+
+  const key = `${token || 'anonymous'}:${url}`;
+  const existing = inflightGetRequests.get(key) as Promise<T> | undefined;
+  if (existing) return existing;
+
+  const request = executeJsonRequest<T>(url, options, token)
+    .finally(() => {
+      if (inflightGetRequests.get(key) === request) inflightGetRequests.delete(key);
+    });
+  inflightGetRequests.set(key, request);
+  return request;
+}
+
+export function _clearApiClientInflightForTests(): void {
+  inflightGetRequests.clear();
+}