fix(server): dedupe remote collection requests (#535)

Author: onmax

src/bundle-server.ts

@@ -93,9 +93,14 @@ export function registerServerBundle(
         '  return async () => {',
         '    if (_cache)',
         '      return _cache',
-        '    const res = await fetch(fetchEndpoint).then(r => r.json())',
-        '    _cache = res',
-        '    return res',
+        '    _cache = fetch(fetchEndpoint).then(r => r.json()).then((data) => {',
+        '      _cache = data',
+        '      return data',
+        '    }).catch((error) => {',
+        '      _cache = undefined',
+        '      throw error',
+        '    })',
+        '    return _cache',
         '  }',
         '}',
         '',

test/server-bundle.test.ts

@@ -0,0 +1,75 @@
+import { addTemplate } from '@nuxt/kit'
+import { afterEach, expect, it, vi } from 'vitest'
+import { registerServerBundle } from '../src/bundle-server'
+import type { NuxtIconModuleContext } from '../src/context'
+
+vi.mock('@nuxt/kit', async importOriginal => ({
+  ...await importOriginal<typeof import('@nuxt/kit')>(),
+  addTemplate: vi.fn(() => ({ dst: '/nuxt-icon-server-bundle.mjs' })),
+}))
+
+afterEach(() => {
+  vi.unstubAllGlobals()
+  vi.clearAllMocks()
+})
+
+async function loadCollection() {
+  registerServerBundle({
+    nuxt: { options: { dev: false, appConfig: {}, nitro: {} } },
+    resolveServerBundle: async () => ({
+      collections: [{ prefix: 'test', fetchEndpoint: 'https://example.com/icons.json' }],
+      remote: false,
+    }),
+  } as unknown as NuxtIconModuleContext)
+
+  const template = vi.mocked(addTemplate).mock.calls[0]![0] as { getContents: () => Promise<string> }
+  const code = await template.getContents()
+  const module = await import(/* @vite-ignore */ `data:text/javascript;base64,${Buffer.from(code).toString('base64')}#${crypto.randomUUID()}`)
+  return module.collections.test as () => Promise<unknown>
+}
+
+it('shares an in-flight collection fetch and caches the resolved data', async () => {
+  const { promise, resolve } = Promise.withResolvers<Response>()
+  const fetch = vi.fn(() => promise)
+  vi.stubGlobal('fetch', fetch)
+  const load = await loadCollection()
+  const first = load()
+  const second = load()
+
+  expect(fetch).toHaveBeenCalledTimes(1)
+  const data = { prefix: 'test', icons: { item: { body: '<path d="M0 0h16v16H0z"/>' } } }
+  resolve(Response.json(data))
+  await expect(first).resolves.toEqual(data)
+  await expect(second).resolves.toEqual(data)
+  await expect(load()).resolves.toEqual(data)
+  expect(fetch).toHaveBeenCalledTimes(1)
+})
+
+it.each(['fetch', 'json'])('retries after a rejected %s operation', async (failure) => {
+  const fetch = vi.fn()
+  if (failure === 'fetch')
+    fetch.mockRejectedValueOnce(new Error('offline'))
+  else
+    fetch.mockResolvedValueOnce(new Response('invalid JSON'))
+  const data = { prefix: 'test', icons: {} }
+  fetch.mockResolvedValue(Response.json(data))
+  vi.stubGlobal('fetch', fetch)
+  const load = await loadCollection()
+
+  await expect(load()).rejects.toThrow()
+  await expect(load()).resolves.toEqual(data)
+  expect(fetch).toHaveBeenCalledTimes(2)
+})
+
+it.each([null, false])('does not retain a falsy collection response: %s', async (value) => {
+  const data = { prefix: 'test', icons: {} }
+  const fetch = vi.fn()
+    .mockResolvedValueOnce(Response.json(value))
+    .mockResolvedValue(Response.json(data))
+  vi.stubGlobal('fetch', fetch)
+  const load = await loadCollection()
+
+  await expect(load()).resolves.toBe(value)
+  await expect(load()).resolves.toEqual(data)
+  expect(fetch).toHaveBeenCalledTimes(2)
+})