Add compile-time DX tests for chat transport types

Co-authored-by: Eric Allam <eric@trigger.dev>

Author: cursoragent

packages/ai/src/chatTransport.types.test.ts

@@ -0,0 +1,81 @@
+import { expectTypeOf, it } from "vitest";
+import type { InferUIMessageChunk, UIMessage } from "ai";
+import {
+  TriggerChatTransport,
+  TriggerChatTransportOptions,
+  type TriggerChatTransportPayload,
+  type TriggerChatTransportRequest,
+  type TriggerChatRunState,
+} from "./index.js";
+import type { RealtimeDefinedStream } from "@trigger.dev/core/v3";
+
+it("infers rich default payload contract", function () {
+  const transport = new TriggerChatTransport({
+    task: "ai-chat",
+    accessToken: "pk_test",
+    stream: "chat-stream",
+  });
+
+  expectTypeOf(transport).toEqualTypeOf<
+    TriggerChatTransport<UIMessage, TriggerChatTransportPayload<UIMessage>>
+  >();
+});
+
+it("requires payload mapper for custom payload types", function () {
+  // @ts-expect-error Custom payload generic requires payloadMapper
+  const invalidOptions: TriggerChatTransportOptions<UIMessage, { prompt: string }> = {
+    task: "ai-chat",
+    accessToken: "pk_test",
+    stream: "chat-stream",
+  };
+
+  expectTypeOf(invalidOptions).toBeObject();
+});
+
+it("types mapper input with rich request context", function () {
+  const options: TriggerChatTransportOptions<
+    UIMessage,
+    { prompt: string; chatId: string; source: string | undefined }
+  > = {
+    task: "ai-chat",
+    accessToken: "pk_test",
+    stream: "chat-stream",
+    payloadMapper: function payloadMapper(request: TriggerChatTransportRequest<UIMessage>) {
+      const firstMessage = request.messages[0];
+      const firstPart = firstMessage?.parts[0];
+      const prompt =
+        firstPart && firstPart.type === "text"
+          ? firstPart.text
+          : "";
+
+      return {
+        prompt,
+        chatId: request.chatId,
+        source: request.request.headers?.["x-source"],
+      };
+    },
+    onTriggeredRun: function onTriggeredRun(state: TriggerChatRunState) {
+      expectTypeOf(state.chatId).toEqualTypeOf<string>();
+      expectTypeOf(state.publicAccessToken).toEqualTypeOf<string>();
+    },
+  };
+
+  expectTypeOf(options.payloadMapper).toBeFunction();
+});
+
+it("accepts typed stream definition objects", function () {
+  const typedStream = {
+    id: "chat-stream",
+    pipe: async function pipe() {
+      throw new Error("not used in type test");
+    },
+  } as unknown as RealtimeDefinedStream<InferUIMessageChunk<UIMessage>>;
+
+  const transport = new TriggerChatTransport({
+    task: "ai-chat",
+    accessToken: "pk_test",
+    stream: typedStream,
+  });
+
+  expectTypeOf(transport).toBeObject();
+});