handle exponential sample rate notation

Author: Lms24

packages/tracing/src/span.ts

@@ -402,7 +402,16 @@ export class Span implements SpanInterface {
     transactionName && setBaggageValue(baggage, 'transaction', transactionName);
     userId && setBaggageValue(baggage, 'userid', userId);
     userSegment && setBaggageValue(baggage, 'usersegment', userSegment);
-    sampelRate && setBaggageValue(baggage, 'samplerate', sampelRate.toString());
+    sampelRate &&
+      setBaggageValue(
+        baggage,
+        'samplerate',
+        // This will make sure that expnent notation (e.g. 1.45e-14) is converted to simple decimal representation
+        // Another edge case would be something like Number.NEGATIVE_INFINITY in which case we could still
+        // add something like .replace(/-?∞/, '0'). For the sake of saving bytes, I'll not add this until
+        // it becomes a problem
+        sampelRate.toLocaleString('fullwide', { useGrouping: false, maximumFractionDigits: 16 }),
+      );
     publicKey && setBaggageValue(baggage, 'publickey', publicKey);
     traceId && setBaggageValue(baggage, 'traceid', traceId);
 

packages/tracing/test/span.test.ts

@@ -453,5 +453,29 @@ describe('Span', () => {
       });
       expect(baggage && getThirdPartyBaggage(baggage)).toStrictEqual('');
     });
+
+    test('exponential sample rate notation is converted to decimal notation', () => {
+      const transaction = new Transaction(
+        {
+          name: 'tx',
+          metadata: {
+            transactionSampling: { rate: 1.45e-14, method: 'client_rate' },
+          },
+        },
+        hub,
+      );
+
+      const baggage = transaction.getBaggage();
+
+      expect(baggage && isSentryBaggageEmpty(baggage)).toBe(false);
+      expect(baggage && getSentryBaggageItems(baggage)).toStrictEqual({
+        release: '1.0.1',
+        environment: 'production',
+        transaction: 'tx',
+        samplerate: '0.0000000000000145',
+        traceid: expect.any(String),
+      });
+      expect(baggage && getThirdPartyBaggage(baggage)).toStrictEqual('');
+    });
   });
 });