use enum for method options

Author: lobsterkatie

packages/tracing/src/hubextensions.ts

@@ -14,6 +14,13 @@ import { IdleTransaction } from './idletransaction';
 import { Transaction } from './transaction';
 import { hasTracingEnabled } from './utils';
 
+const SAMPLING_METHODS = {
+  explicit: 'explicitly_set',
+  sampler: 'client_sampler',
+  rate: 'client_rate',
+  inheritance: 'inheritance',
+};
+
 /** Returns all trace headers that are currently on the top scope. */
 function traceHeaders(this: Hub): { [key: string]: string } {
   const scope = this.getScope();
@@ -52,7 +59,7 @@ function sample<T extends Transaction>(hub: Hub, transaction: T, samplingContext
 
   // if the user has forced a sampling decision by passing a `sampled` value in their transaction context, go with that
   if (transaction.sampled !== undefined) {
-    transaction.tags = { ...transaction.tags, __sentry_samplingMethod: 'explicitly_set' };
+    transaction.tags = { ...transaction.tags, __sentry_samplingMethod: SAMPLING_METHODS.explicit };
     return transaction;
   }
 
@@ -64,18 +71,18 @@ function sample<T extends Transaction>(hub: Hub, transaction: T, samplingContext
     // cast the rate to a number first in case it's a boolean
     transaction.tags = {
       ...transaction.tags,
-      __sentry_samplingMethod: 'client_sampler',
+      __sentry_samplingMethod: SAMPLING_METHODS.sampler,
       __sentry_sampleRate: String(Number(sampleRate)),
     };
   } else if (samplingContext.parentSampled !== undefined) {
     sampleRate = samplingContext.parentSampled;
-    transaction.tags = { ...transaction.tags, __sentry_samplingMethod: 'inheritance' };
+    transaction.tags = { ...transaction.tags, __sentry_samplingMethod: SAMPLING_METHODS.inheritance };
   } else {
     sampleRate = options.tracesSampleRate;
     // cast the rate to a number first in case it's a boolean
     transaction.tags = {
       ...transaction.tags,
-      __sentry_samplingMethod: 'client_rate',
+      __sentry_samplingMethod: SAMPLING_METHODS.rate,
       __sentry_sampleRate: String(Number(sampleRate)),
     };
   }