feat(sveltekit): Only inject fetch proxy script for SvelteKit < 2.16.0

Author: Lms24

packages/sveltekit/src/server/handle.ts

@@ -14,7 +14,7 @@ import {
   winterCGRequestToRequestData,
   withIsolationScope,
 } from '@sentry/core';
-import type { Handle, ResolveOptions } from '@sveltejs/kit';
+import { VERSION, type Handle, type ResolveOptions } from '@sveltejs/kit';
 
 import { DEBUG_BUILD } from '../common/debug-build';
 import { flushIfServerless, getTracePropagationData, sendErrorToSentry } from './utils';
@@ -95,7 +95,7 @@ export function addSentryCodeToPage(options: { injectFetchProxyScript: boolean }
 export function sentryHandle(handlerOptions?: SentryHandleOptions): Handle {
   const options: Required<SentryHandleOptions> = {
     handleUnknownRoutes: false,
-    injectFetchProxyScript: true,
+    injectFetchProxyScript: isFetchProxyRequired(VERSION),
     ...handlerOptions,
   };
 
@@ -177,3 +177,19 @@ async function instrumentHandle(
     await flushIfServerless();
   }
 }
+
+/**
+ * We only need to inject the fetch proxy script for SvelteKit versions < 2.16.0.
+ * Exported only for testing.
+ */
+export function isFetchProxyRequired(version: string): boolean {
+  try {
+    const [major, minor] = version.trim().replace(/-.*/, '').split('.').map(Number);
+    if (major != null && minor != null && (major > 2 || (major === 2 && minor >= 16))) {
+      return false;
+    }
+  } catch {
+    // ignore
+  }
+  return true;
+}

packages/sveltekit/test/server/handle.test.ts

@@ -14,7 +14,7 @@ import type { Handle } from '@sveltejs/kit';
 import { redirect } from '@sveltejs/kit';
 import { vi } from 'vitest';
 
-import { FETCH_PROXY_SCRIPT, addSentryCodeToPage, sentryHandle } from '../../src/server/handle';
+import { FETCH_PROXY_SCRIPT, addSentryCodeToPage, isFetchProxyRequired, sentryHandle } from '../../src/server/handle';
 import { getDefaultNodeClientOptions } from '../utils';
 
 const mockCaptureException = vi.spyOn(SentryNode, 'captureException').mockImplementation(() => 'xx');
@@ -462,3 +462,20 @@ describe('addSentryCodeToPage', () => {
     expect(transformed).not.toContain(`<script >${FETCH_PROXY_SCRIPT}</script>`);
   });
 });
+
+describe('isFetchProxyRequired', () => {
+  it.each(['2.16.0', '2.16.1', '2.17.0', '3.0.0', '3.0.0-alpha.0'])(
+    'returns false if the version is greater than or equal to 2.16.0 (%s)',
+    version => {
+      expect(isFetchProxyRequired(version)).toBe(false);
+    },
+  );
+
+  it.each(['2.15.0', '2.15.1', '1.30.0', '1.0.0'])('returns true if the version is lower than 2.16.0 (%s)', version => {
+    expect(isFetchProxyRequired(version)).toBe(true);
+  });
+
+  it.each(['invalid', 'a.b.c'])('returns true for an invalid version (%s)', version => {
+    expect(isFetchProxyRequired(version)).toBe(true);
+  });
+});