feat(nextjs): Emit warning for conflicting treeshaking / debug settings

packages/nextjs/src/client/index.ts

@@ -5,6 +5,7 @@ import type { Client, EventProcessor, Integration } from '@sentry/core';
 import { addEventProcessor, applySdkMetadata, consoleSandbox, getGlobalScope, GLOBAL_OBJ } from '@sentry/core';
 import type { BrowserOptions } from '@sentry/react';
 import { getDefaultIntegrations as getReactDefaultIntegrations, init as reactInit } from '@sentry/react';
+import { DEBUG_BUILD } from '../common/debug-build';
 import { devErrorSymbolicationEventProcessor } from '../common/devErrorSymbolicationEventProcessor';
 import { getVercelEnv } from '../common/getVercelEnv';
 import { isRedirectNavigationError } from '../common/nextNavigationErrorUtils';
@@ -48,6 +49,15 @@ export function init(options: BrowserOptions): Client | undefined {
   }
   clientIsInitialized = true;
 
+  if (!DEBUG_BUILD && options.debug) {
+    consoleSandbox(() => {
+      // eslint-disable-next-line no-console
+      console.warn(
+        '[@sentry/nextjs] You have enabled `debug: true`, but Sentry debug logging was removed from your bundle (likely via `withSentryConfig({ disableLogger: true })` / `webpack.treeshake.removeDebugLogging: true`). Set that option to `false` to see Sentry debug output.',
+      );
+    });
+  }
+
   // Remove cached trace meta tags for ISR/SSG pages before initializing
   // This prevents the browser tracing integration from using stale trace IDs
   if (typeof __SENTRY_TRACING__ === 'undefined' || __SENTRY_TRACING__) {

packages/nextjs/src/edge/index.ts

@@ -22,6 +22,7 @@ import {
 import { getScopesFromContext } from '@sentry/opentelemetry';
 import type { VercelEdgeOptions } from '@sentry/vercel-edge';
 import { getDefaultIntegrations, init as vercelEdgeInit } from '@sentry/vercel-edge';
+import { DEBUG_BUILD } from '../common/debug-build';
 import { ATTR_NEXT_SPAN_TYPE } from '../common/nextSpanAttributes';
 import { TRANSACTION_ATTR_SHOULD_DROP_TRANSACTION } from '../common/span-attributes-with-logic-attached';
 import { addHeadersAsAttributes } from '../common/utils/addHeadersAsAttributes';
@@ -55,6 +56,13 @@ export function init(options: VercelEdgeOptions = {}): void {
     return;
   }
 
+  if (!DEBUG_BUILD && options.debug) {
+    // eslint-disable-next-line no-console
+    console.warn(
+      '[@sentry/nextjs] You have enabled `debug: true`, but Sentry debug logging was removed from your bundle (likely via `withSentryConfig({ disableLogger: true })` / `webpack.treeshake.removeDebugLogging: true`). Set that option to `false` to see Sentry debug output.',
+    );
+  }
+
   const customDefaultIntegrations = getDefaultIntegrations(options);
 
   // This value is injected at build time, based on the output directory specified in the build config. Though a default

packages/nextjs/src/server/index.ts

@@ -96,6 +96,13 @@ export function init(options: NodeOptions): NodeClient | undefined {
     return;
   }
 
+  if (!DEBUG_BUILD && options.debug) {
+    // eslint-disable-next-line no-console
+    console.warn(
+      '[@sentry/nextjs] You have enabled `debug: true`, but Sentry debug logging was removed from your bundle (likely via `withSentryConfig({ disableLogger: true })` / `webpack.treeshake.removeDebugLogging: true`). Set that option to `false` to see Sentry debug output.',
+    );
+  }
+
   const customDefaultIntegrations = getDefaultIntegrations(options)
     .filter(integration => integration.name !== 'Http')
     .concat(

packages/nextjs/test/config/conflictingDebugOptions.test.ts

@@ -0,0 +1,82 @@
+import { JSDOM } from 'jsdom';
+import { afterAll, afterEach, beforeAll, describe, expect, it, vi } from 'vitest';
+
+const TEST_DSN = 'https://[email protected]/1337';
+
+function didWarnAboutDebugRemoved(warnSpy: ReturnType<typeof vi.spyOn>): boolean {
+  return warnSpy.mock.calls.some(call =>
+    call.some(
+      arg =>
+        typeof arg === 'string' &&
+        arg.includes('You have enabled `debug: true`') &&
+        arg.includes('debug logging was removed from your bundle'),
+    ),
+  );
+}
+
+describe('debug: true + removeDebugLogging warning', () => {
+  let dom: JSDOM;
+  let originalDocument: unknown;
+  let originalLocation: unknown;
+  let originalAddEventListener: unknown;
+
+  beforeAll(() => {
+    dom = new JSDOM('<!doctype html><html><head></head><body></body></html>', { url: 'https://example.com/' });
+
+    originalDocument = (globalThis as any).document;
+    originalLocation = (globalThis as any).location;
+    originalAddEventListener = (globalThis as any).addEventListener;
+
+    Object.defineProperty(globalThis, 'document', { value: dom.window.document, writable: true });
+    Object.defineProperty(globalThis, 'location', { value: dom.window.location, writable: true });
+    Object.defineProperty(globalThis, 'addEventListener', { value: () => undefined, writable: true });
+  });
+
+  afterAll(() => {
+    Object.defineProperty(globalThis, 'document', { value: originalDocument, writable: true });
+    Object.defineProperty(globalThis, 'location', { value: originalLocation, writable: true });
+    Object.defineProperty(globalThis, 'addEventListener', { value: originalAddEventListener, writable: true });
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    vi.resetModules();
+    vi.unmock('../../src/common/debug-build.js');
+    delete process.env.NEXT_OTEL_FETCH_DISABLED;
+    delete process.env.NEXT_PHASE;
+  });
+
+  it('warns on client/server/edge when debug is true but DEBUG_BUILD is false', async () => {
+    vi.doMock('../../src/common/debug-build.js', () => ({ DEBUG_BUILD: false }));
+
+    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const client = await import('../../src/client/index.js');
+    client.init({ dsn: TEST_DSN, debug: true } as any);
+
+    const server = await import('../../src/server/index.js');
+    server.init({ dsn: TEST_DSN, debug: true } as any);
+
+    const edge = await import('../../src/edge/index.js');
+    edge.init({ dsn: TEST_DSN, debug: true } as any);
+
+    expect(didWarnAboutDebugRemoved(warnSpy)).toBe(true);
+  });
+
+  it('does not emit that warning when DEBUG_BUILD is true', async () => {
+    vi.doMock('../../src/common/debug-build.js', () => ({ DEBUG_BUILD: true }));
+
+    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const client = await import('../../src/client/index.js');
+    client.init({ dsn: TEST_DSN, debug: true } as any);
+
+    const server = await import('../../src/server/index.js');
+    server.init({ dsn: TEST_DSN, debug: true } as any);
+
+    const edge = await import('../../src/edge/index.js');
+    edge.init({ dsn: TEST_DSN, debug: true } as any);
+
+    expect(didWarnAboutDebugRemoved(warnSpy)).toBe(false);
+  });
+});