test(nextjs): Test error trace linking for Vercel AI in Next.js (#17200)

Add a test to verify that error trace linking works in Next.js and
correctly bubbles up to the parent span.

Author: RulaKhaled

dev-packages/e2e-tests/test-applications/nextjs-15/app/ai-error-test/page.tsx

@@ -0,0 +1,50 @@
+import { generateText } from 'ai';
+import { MockLanguageModelV1 } from 'ai/test';
+import { z } from 'zod';
+import * as Sentry from '@sentry/nextjs';
+
+export const dynamic = 'force-dynamic';
+
+// Error trace handling in tool calls
+async function runAITest() {
+  const result = await generateText({
+    experimental_telemetry: { isEnabled: true },
+    model: new MockLanguageModelV1({
+      doGenerate: async () => ({
+        rawCall: { rawPrompt: null, rawSettings: {} },
+        finishReason: 'tool-calls',
+        usage: { promptTokens: 15, completionTokens: 25 },
+        text: 'Tool call completed!',
+        toolCalls: [
+          {
+            toolCallType: 'function',
+            toolCallId: 'call-1',
+            toolName: 'getWeather',
+            args: '{ "location": "San Francisco" }',
+          },
+        ],
+      }),
+    }),
+    tools: {
+      getWeather: {
+        parameters: z.object({ location: z.string() }),
+        execute: async args => {
+          throw new Error('Tool call failed');
+        },
+      },
+    },
+    prompt: 'What is the weather in San Francisco?',
+  });
+}
+
+export default async function Page() {
+  await Sentry.startSpan({ op: 'function', name: 'ai-error-test' }, async () => {
+    return await runAITest();
+  });
+
+  return (
+    <div>
+      <h1>AI Test Results</h1>
+    </div>
+  );
+}

dev-packages/e2e-tests/test-applications/nextjs-15/tests/ai-error.test.ts

@@ -0,0 +1,40 @@
+import { expect, test } from '@playwright/test';
+import { waitForTransaction, waitForError } from '@sentry-internal/test-utils';
+
+test('should create AI spans with correct attributes and error linking', async ({ page }) => {
+  const aiTransactionPromise = waitForTransaction('nextjs-15', async transactionEvent => {
+    return transactionEvent.transaction === 'GET /ai-error-test';
+  });
+
+  const errorEventPromise = waitForError('nextjs-15', async errorEvent => {
+    return errorEvent.exception?.values?.[0]?.value?.includes('Tool call failed');
+  });
+
+  await page.goto('/ai-error-test');
+
+  const aiTransaction = await aiTransactionPromise;
+  const errorEvent = await errorEventPromise;
+
+  expect(aiTransaction).toBeDefined();
+  expect(aiTransaction.transaction).toBe('GET /ai-error-test');
+
+  const spans = aiTransaction.spans || [];
+
+  // Each generateText call should create 2 spans: one for the pipeline and one for doGenerate
+  // Plus a span for the tool call
+  // TODO: For now, this is sadly not fully working - the monkey patching of the ai package is not working
+  // because of this, only spans that are manually opted-in at call time will be captured
+  // this may be fixed by https://github.com/vercel/ai/pull/6716 in the future
+  const aiPipelineSpans = spans.filter(span => span.op === 'gen_ai.invoke_agent');
+  const aiGenerateSpans = spans.filter(span => span.op === 'gen_ai.generate_text');
+  const toolCallSpans = spans.filter(span => span.op === 'gen_ai.execute_tool');
+
+  expect(aiPipelineSpans.length).toBeGreaterThanOrEqual(1);
+  expect(aiGenerateSpans.length).toBeGreaterThanOrEqual(1);
+  expect(toolCallSpans.length).toBeGreaterThanOrEqual(0);
+
+  expect(errorEvent).toBeDefined();
+
+  //Verify error is linked to the same trace as the transaction
+  expect(errorEvent?.contexts?.trace?.trace_id).toBe(aiTransaction.contexts?.trace?.trace_id);
+});