chore: add dataloader reference (#4073)

package.json

@@ -12,6 +12,7 @@
     "dev-www": "turbo --filter www dev",
     "test": "turbo --filter \"@trpc/tests\" test",
     "test-watch": "cd packages/tests && pnpm test-watch",
+    "vitest": "cd packages/tests && pnpm vitest",
     "oldlint": "eslint --ext \".js,.ts,.tsx\" --ignore-path .gitignore . --report-unused-disable-directives",
     "lint": "turbo lint",
     "lint-fix": "turbo lint -- --fix && manypkg fix",

packages/tests/package.json

@@ -34,6 +34,7 @@
     "@vitest/ui": "^0.28.5",
     "abort-controller": "^3.0.0",
     "concurrently": "^7.6.0",
+    "dataloader": "^2.2.2",
     "devalue": "^4.0.0",
     "eslint": "^8.30.0",
     "expect-type": "^0.15.0",

packages/tests/showcase/dataloader.test.ts

@@ -0,0 +1,61 @@
+import { routerToServerAndClientNew } from '../server/___testHelpers';
+import { inferAsyncReturnType, initTRPC } from '@trpc/server';
+import { CreateHTTPContextOptions } from '@trpc/server/adapters/standalone';
+import DataLoader from 'dataloader';
+import { konn } from 'konn';
+import { z } from 'zod';
+
+const posts = [
+  {
+    id: 1,
+    text: 'foo',
+  },
+  {
+    id: 2,
+    text: 'bar',
+  },
+];
+
+function createContext(_opts: CreateHTTPContextOptions) {
+  return {
+    postLoader: new DataLoader(async (ids: ReadonlyArray<number>) => {
+      return ids.map((id) => posts.find((post) => post.id === id));
+    }),
+  };
+}
+type Context = inferAsyncReturnType<typeof createContext>;
+
+const ctx = konn()
+  .beforeEach(() => {
+    const t = initTRPC.context<Context>().create();
+
+    const appRouter = t.router({
+      post: t.router({
+        byId: t.procedure
+          .input(
+            z.object({
+              id: z.number(),
+            }),
+          )
+          .query(({ input, ctx }) => ctx.postLoader.load(input.id)),
+      }),
+    });
+    return routerToServerAndClientNew(appRouter, {
+      server: {
+        createContext,
+      },
+    });
+  })
+  .afterEach(async (ctx) => {
+    await ctx?.close?.();
+  })
+  .done();
+
+test('dataloader', async () => {
+  const result = await Promise.all([
+    ctx.proxy.post.byId.query({ id: 1 }),
+    ctx.proxy.post.byId.query({ id: 2 }),
+  ]);
+
+  expect(result).toEqual([posts[0], posts[1]]);
+});