move hasSpansEnabled gate into instrumentation setup

Author: s1gr1d

packages/nextjs/src/server/index.ts

@@ -11,7 +11,6 @@ import {
   getRootSpan,
   getVercelEnv,
   GLOBAL_OBJ,
-  hasSpansEnabled,
 } from '@sentry/core';
 import type { NodeClient, NodeOptions } from '@sentry/node';
 import { getDefaultIntegrations, httpIntegration, init as nodeInit } from '@sentry/node';
@@ -143,9 +142,7 @@ export function init(options: NodeOptions): NodeClient | undefined {
     customDefaultIntegrations.push(distDirRewriteFramesIntegration({ distDirName }));
   }
 
-  if (hasSpansEnabled(options)) {
-    customDefaultIntegrations.push(nextjsUseCacheIntegration());
-  }
+  customDefaultIntegrations.push(nextjsUseCacheIntegration());
 
   // Detect if running on OpenNext/Cloudflare and get runtime config
   const cloudflareConfig = getCloudflareRuntimeConfig();

packages/nextjs/src/server/useCacheInstrumentation.ts

@@ -10,6 +10,7 @@ import {
   getActiveSpan,
   getClient,
   hasSpanStreamingEnabled,
+  hasSpansEnabled,
   SEMANTIC_ATTRIBUTE_CACHE_HIT,
   SEMANTIC_ATTRIBUTE_CACHE_KEY,
   SEMANTIC_ATTRIBUTE_SENTRY_ORIGIN,
@@ -279,8 +280,11 @@ export function _instrumentUseCacheHandlers(): void {
 export const nextjsUseCacheIntegration = defineIntegration(() => {
   return {
     name: INTEGRATION_NAME,
-    setupOnce() {
-      _instrumentUseCacheHandlers();
+    setup(client) {
+      // The resolved client options also cover tracing enabled via `SENTRY_TRACES_SAMPLE_RATE`.
+      if (hasSpansEnabled(client.getOptions())) {
+        _instrumentUseCacheHandlers();
+      }
     },
   };
 });

packages/nextjs/test/serverSdk.test.ts

@@ -100,24 +100,48 @@ describe('Server init()', () => {
       expect(onUncaughtExceptionIntegration).toBeDefined();
     });
 
-    it('adds the `use cache` integration when tracing is enabled', () => {
-      init({ tracesSampleRate: 1 });
+    describe('`use cache` integration', () => {
+      const CACHE_HANDLERS_INSTRUMENTED = Symbol.for('sentry.nextjs.cacheHandlersInstrumented');
+      const DSN = 'https://public@dsn.ingest.sentry.io/1337';
 
-      expect(nodeInit).toHaveBeenLastCalledWith(
-        expect.objectContaining({
-          defaultIntegrations: expect.arrayContaining([expect.objectContaining({ name: 'NextjsUseCache' })]),
-        }),
-      );
-    });
+      function isUseCacheInstrumented(): boolean {
+        return (globalThis as Record<symbol, unknown>)[CACHE_HANDLERS_INSTRUMENTED] === true;
+      }
 
-    it('does not add the `use cache` integration when tracing is disabled', () => {
-      init({});
+      afterEach(() => {
+        vi.unstubAllEnvs();
+        Reflect.deleteProperty(globalThis, CACHE_HANDLERS_INSTRUMENTED);
+      });
 
-      expect(nodeInit).toHaveBeenLastCalledWith(
-        expect.objectContaining({
-          defaultIntegrations: expect.not.arrayContaining([expect.objectContaining({ name: 'NextjsUseCache' })]),
-        }),
-      );
+      it('adds the integration to the default integrations', () => {
+        init({});
+
+        expect(nodeInit).toHaveBeenLastCalledWith(
+          expect.objectContaining({
+            defaultIntegrations: expect.arrayContaining([expect.objectContaining({ name: 'NextjsUseCache' })]),
+          }),
+        );
+      });
+
+      it('instruments the cache handlers when tracing is enabled', () => {
+        init({ dsn: DSN, tracesSampleRate: 1 });
+
+        expect(isUseCacheInstrumented()).toBe(true);
+      });
+
+      it('instruments the cache handlers when tracing is enabled via `SENTRY_TRACES_SAMPLE_RATE`', () => {
+        vi.stubEnv('SENTRY_TRACES_SAMPLE_RATE', '1');
+
+        init({ dsn: DSN });
+
+        expect(isUseCacheInstrumented()).toBe(true);
+      });
+
+      it('does not instrument the cache handlers when tracing is disabled', () => {
+        init({ dsn: DSN });
+
+        expect(isUseCacheInstrumented()).toBe(false);
+      });
     });
 
     it('supports passing unrelated integrations through options', () => {