sentry [nfc]: move is-active test into the main code base

src/__tests__/sentry-test.js

@@ -1,28 +1,29 @@
 // @flow
 
 import * as Sentry from '@sentry/react-native';
+import { isSentryActive } from '../sentry';
 
 describe('sentry', () => {
   describe('is usable without initialization', () => {
-    const expectSentryUninitialized = () => {
-      // Hub#getClient() is documented as possibly returning undefined, but the
-      // significance of `undefined` is not. In practice, it appears to be
-      // `undefined` exactly when `Sentry.init()` has not yet been called.
-      expect(Sentry.getCurrentHub().getClient()).toBeUndefined();
-    };
+    // Sentry shouldn't be active at all in debug mode -- certainly not while
+    // we're specifically testing that its entry points can be used while it's
+    // uninitialized.
+    beforeEach(() => {
+      expect(isSentryActive()).toBeFalse();
+    });
 
-    test('breadcrumbs', () => {
-      expectSentryUninitialized();
+    afterEach(() => {
+      expect(isSentryActive()).toBeFalse();
+    });
 
+    test('breadcrumbs', () => {
       Sentry.addBreadcrumb({
         message: 'test message',
         level: Sentry.Severity.Debug,
       });
     });
 
     test('exception reporting', () => {
-      expectSentryUninitialized();
-
       // The text here is intended to prevent some hypothetical future reader of
       // Sentry event logs dismissing the error as harmless expected noise, in
       // case Sentry is somehow actually initialized at this point.

src/sentry.js

@@ -3,6 +3,21 @@ import * as Sentry from '@sentry/react-native';
 import DeviceInfo from 'react-native-device-info';
 import config from './config';
 
+export const isSentryActive = (): boolean => {
+  // Hub#getClient() is documented as possibly returning undefined, but the
+  // significance of `undefined` is not. In practice, it appears to be
+  // `undefined` exactly when `Sentry.init()` has not yet been called.
+  const client = Sentry.getCurrentHub().getClient();
+
+  /* The `enabled` option in getOptions() is theoretically togglable at runtime:
+     https://github.com/getsentry/sentry-javascript/issues/2039#issuecomment-486674574
+     We avoid this, however, as it will only toggle the JavaScript SDK and not
+     the lower-level native-code SDKs. */
+  // return (client && client.getOptions().enabled) ?? false;
+
+  return !!client;
+};
+
 const preventNoise = (): void => {
   /* Sentry should not normally be used in debug mode. (For one thing, the
      debug-mode build process doesn't ordinarily create bundles or .map files,