Fail gracefully if config is invalid

README.md

@@ -98,7 +98,7 @@ The Worker simply calls `fetch(request)` to reach your origin and separately pos
 
 ## Runtime Behavior
 
-- Receives each incoming request, proxies to origin with `fetch`, and returns the origin response.
+- Receives each incoming request, proxies to origin with `fetch`, and returns the origin response. If configuration is invalid, logs an error and just proxies (no tracking).
 - Measures server time (`pf_srv` in seconds), status, and response bytes from `Content-Length` when present.
 - Builds a Matomo payload with `idsite`, `rec:1`, `recMode:1`, `url`, `source:'Cloudflare'`, `cdt` (UTC `YYYY-MM-DD HH:mm:ss`), and `ua`.
 - Skips tracking when `URL_EXCLUDE_REGEX` matches; detects downloads via `DOCUMENT_REGEX`; disallowed UAs are skipped by `USER_AGENT_ALLOWLIST_REGEX`.

src/index.ts

@@ -41,12 +41,13 @@ export default {
     env: Env,
     ctx: WorkerContext
   ): Promise<Response> {
-    let config: MatomoConfig;
+    let config: MatomoConfig | null = null;
     try {
       config = getConfig(env);
     } catch (err) {
       const message = err instanceof Error ? err.message : String(err);
-      return new Response(`Configuration error: ${message}`, { status: 500 });
+      console.error('Configuration error', { error: message });
+      return fetch(request);
     }
     const log = createLogger(config.logLevel);
     const start = Date.now();

tests/index.test.ts

@@ -118,13 +118,25 @@ describe('Worker fetch handler', () => {
     consoleWarn.mockRestore();
   });
 
-  it('returns 500 when config is invalid', async () => {
+  it('returns origin response when config is invalid and skips tracking', async () => {
+    const originResponse = new Response('origin', { status: 200 });
+    const fetchMock = vi.fn().mockResolvedValue(originResponse);
+    global.fetch = fetchMock as unknown as typeof fetch;
+    const sendSpy = vi
+      .spyOn(http, 'sendMatomoHit')
+      .mockResolvedValue(undefined);
+
     const response = await worker.fetch(
       new Request('https://example.com/path'),
       { MATOMO_SITE_ID: '7' } as never,
       { waitUntil }
     );
-    expect(response.status).toBe(500);
+    expect(response.status).toBe(200);
     expect(waitUntil).not.toHaveBeenCalled();
+    expect(sendSpy).not.toHaveBeenCalled();
+    expect(consoleSpies.error).toHaveBeenCalledWith(
+      'Configuration error',
+      expect.objectContaining({ error: expect.stringContaining('MATOMO_URL') })
+    );
   });
 });