feat(utils): Introduce getGlobalSingleton helper (#4860)

This helper abstracts away the logic of getting an variable from the global `__SENTRY__` object. It does this by introducing a new `getGlobalSingleton` utility function.

For now, this is used by the event processors and hub logic. In an upcoming PR, we'll update the logger logic to also use this utility.

Author: AbhiPrasad

packages/hub/src/hub.ts

@@ -20,7 +20,15 @@ import {
   TransactionContext,
   User,
 } from '@sentry/types';
-import { consoleSandbox, dateTimestampInSeconds, getGlobalObject, isNodeEnv, logger, uuid4 } from '@sentry/utils';
+import {
+  consoleSandbox,
+  dateTimestampInSeconds,
+  getGlobalObject,
+  getGlobalSingleton,
+  isNodeEnv,
+  logger,
+  uuid4,
+} from '@sentry/utils';
 
 import { IS_DEBUG_BUILD } from './flags';
 import { Scope } from './scope';
@@ -617,10 +625,7 @@ function hasHubOnCarrier(carrier: Carrier): boolean {
  * @hidden
  */
 export function getHubFromCarrier(carrier: Carrier): Hub {
-  if (carrier && carrier.__SENTRY__ && carrier.__SENTRY__.hub) return carrier.__SENTRY__.hub;
-  carrier.__SENTRY__ = carrier.__SENTRY__ || {};
-  carrier.__SENTRY__.hub = new Hub();
-  return carrier.__SENTRY__.hub;
+  return getGlobalSingleton<Hub>('hub', () => new Hub(), carrier);
 }
 
 /**
@@ -631,7 +636,7 @@ export function getHubFromCarrier(carrier: Carrier): Hub {
  */
 export function setHubOnCarrier(carrier: Carrier, hub: Hub): boolean {
   if (!carrier) return false;
-  carrier.__SENTRY__ = carrier.__SENTRY__ || {};
-  carrier.__SENTRY__.hub = hub;
+  const __SENTRY__ = (carrier.__SENTRY__ = carrier.__SENTRY__ || {});
+  __SENTRY__.hub = hub;
   return true;
 }

packages/hub/src/scope.ts

@@ -18,7 +18,7 @@ import {
   Transaction,
   User,
 } from '@sentry/types';
-import { dateTimestampInSeconds, getGlobalObject, isPlainObject, isThenable, SyncPromise } from '@sentry/utils';
+import { dateTimestampInSeconds, getGlobalSingleton, isPlainObject, isThenable, SyncPromise } from '@sentry/utils';
 
 import { Session } from './session';
 
@@ -522,12 +522,7 @@ export class Scope implements ScopeInterface {
  * Returns the global event processors.
  */
 function getGlobalEventProcessors(): EventProcessor[] {
-  /* eslint-disable @typescript-eslint/no-explicit-any, @typescript-eslint/no-unsafe-member-access  */
-  const global = getGlobalObject<any>();
-  global.__SENTRY__ = global.__SENTRY__ || {};
-  global.__SENTRY__.globalEventProcessors = global.__SENTRY__.globalEventProcessors || [];
-  return global.__SENTRY__.globalEventProcessors;
-  /* eslint-enable @typescript-eslint/no-explicit-any, @typescript-eslint/no-unsafe-member-access */
+  return getGlobalSingleton<EventProcessor[]>('globalEventProcessors', () => []);
 }
 
 /**

packages/utils/src/global.ts

@@ -44,3 +44,21 @@ export function getGlobalObject<T>(): T & SentryGlobal {
       : fallbackGlobalObject
   ) as T & SentryGlobal;
 }
+
+/**
+ * Returns a global singleton contained in the global `__SENTRY__` object.
+ *
+ * If the singleton doesn't already exist in `__SENTRY__`, it will be created using the given factory
+ * function and added to the `__SENTRY__` object.
+ *
+ * @param name name of the global singleton on __SENTRY__
+ * @param creator creator Factory function to create the singleton if it doesn't already exist on `__SENTRY__`
+ * @param obj (Optional) The global object on which to look for `__SENTRY__`, if not `getGlobalObject`'s return value
+ * @returns the singleton
+ */
+export function getGlobalSingleton<T>(name: keyof SentryGlobal['__SENTRY__'], creator: () => T, obj?: unknown): T {
+  const global = (obj || getGlobalObject()) as SentryGlobal;
+  const __SENTRY__ = (global.__SENTRY__ = global.__SENTRY__ || {});
+  const singleton = __SENTRY__[name] || (__SENTRY__[name] = creator());
+  return singleton;
+}