fix(fetch): emit final streamJSON line without trailing newline

packages/fetch/src/stream.test.ts

@@ -1,6 +1,6 @@
 import { Readable } from "stream";
 import { describe, expect, it, test } from "vitest";
-import { parseDataLine, streamSse } from "./stream.js";
+import { parseDataLine, streamJSON, streamSse } from "./stream.js";
 
 function createMockResponse(sseLines: string[]): Response {
   // Create a Readable stream that emits the SSE lines
@@ -21,6 +21,23 @@ function createMockResponse(sseLines: string[]): Response {
   } as unknown as Response;
 }
 
+function createRawMockResponse(chunks: string[]): Response {
+  const stream = new Readable({
+    read() {
+      for (const chunk of chunks) {
+        this.push(chunk);
+      }
+      this.push(null);
+    },
+  }) as any;
+
+  return {
+    status: 200,
+    body: stream,
+    text: async () => "",
+  } as unknown as Response;
+}
+
 describe("streamSse", () => {
   it("yields parsed SSE data objects that ends with `data:[DONE]`", async () => {
     const sseLines = [
@@ -63,6 +80,19 @@ describe("streamSse", () => {
   });
 });
 
+describe("streamJSON", () => {
+  it("yields the final JSON object even without a trailing newline", async () => {
+    const response = createRawMockResponse(['{"foo":"bar"}\n', '{"baz":42}']);
+
+    const results = [];
+    for await (const data of streamJSON(response)) {
+      results.push(data);
+    }
+
+    expect(results).toEqual([{ foo: "bar" }, { baz: 42 }]);
+  });
+});
+
 describe("parseDataLine", () => {
   test("parseDataLine should parse valid JSON data with 'data: ' prefix", () => {
     const line = 'data: {"message":"hello","status":"ok"}';

packages/fetch/src/stream.ts

@@ -166,4 +166,13 @@ export async function* streamJSON(response: Response): AsyncGenerator<any> {
       buffer = buffer.slice(position + 1);
     }
   }
+
+  if (buffer.length > 0) {
+    try {
+      const data = JSON.parse(buffer);
+      yield data;
+    } catch (e) {
+      throw new Error(`Malformed JSON sent from server: ${buffer}`);
+    }
+  }
 }