fix(utils): Normalize when serializing envelope (#5851)

Author: Luca Forstner

packages/utils/src/envelope.ts

@@ -8,6 +8,7 @@ import {
   TextEncoderInternal,
 } from '@sentry/types';
 
+import { normalize } from './normalize';
 import { dropUndefinedKeys } from './object';
 
 /**
@@ -67,9 +68,24 @@ export function serializeEnvelope(envelope: Envelope, textEncoder?: TextEncoderI
   }
 
   for (const item of items) {
-    const [itemHeaders, payload] = item as typeof items[number];
+    const [itemHeaders, payload] = item;
+
     append(`\n${JSON.stringify(itemHeaders)}\n`);
-    append(typeof payload === 'string' || payload instanceof Uint8Array ? payload : JSON.stringify(payload));
+
+    if (typeof payload === 'string' || payload instanceof Uint8Array) {
+      append(payload);
+    } else {
+      let stringifiedPayload: string;
+      try {
+        stringifiedPayload = JSON.stringify(payload);
+      } catch (e) {
+        // In case, despite all our efforts to keep `payload` circular-dependency-free, `JSON.strinify()` still
+        // fails, we try again after normalizing it again with infinite normalization depth. This of course has a
+        // performance impact but in this case a performance hit is better than throwing.
+        stringifiedPayload = JSON.stringify(normalize(payload));
+      }
+      append(stringifiedPayload);
+    }
   }
 
   return typeof parts === 'string' ? parts : concatBuffers(parts);

packages/utils/test/envelope.test.ts

@@ -58,6 +58,21 @@ describe('envelope', () => {
         Uint8Array.from([7, 8, 9, 10, 11, 12]),
       ]);
     });
+
+    it("doesn't throw when being passed a an envelope that contains a circular item payload", () => {
+      const chicken: { egg?: unknown } = {};
+      const egg = { chicken };
+      chicken.egg = chicken;
+
+      const env = createEnvelope<EventEnvelope>({ event_id: 'aa3ff046696b4bc6b609ce6d28fde9e2', sent_at: '123' }, [
+        [{ type: 'event' }, egg],
+      ]);
+
+      const serializedEnvelope = serializeEnvelope(env, new TextEncoder());
+      const [, , serializedBody] = serializedEnvelope.toString().split('\n');
+
+      expect(serializedBody).toBe('{"chicken":{"egg":"[Circular ~]"}}');
+    });
   });
 
   describe('addItemToEnvelope()', () => {