feat(expo): Warn when prebuilt native projects are missing Sentry config

When using the Sentry Expo Plugin with prebuilt native projects, users
need to run `npx expo prebuild --clean` to apply the native changes.
Without this step, source maps upload and native crash reporting won't
work correctly.

This adds a check in `getSentryExpoConfig()` that runs at Metro startup
and inspects existing ios/android directories for Sentry markers:
- iOS: looks for `sentry-xcode` or `Upload Debug Symbols to Sentry`
  in the pbxproj file
- Android: looks for `sentry.gradle` in app/build.gradle

The check only runs for Expo projects (detected via package.json) and
is fully wrapped in try/catch to never crash Metro startup.

Closes #4640

Author: alwx

packages/core/src/js/tools/metroconfig.ts

@@ -10,6 +10,7 @@ import type { DefaultConfigOptions } from './vendor/expo/expoconfig';
 
 import { enableLogger } from './enableLogger';
 import { withSentryMiddleware } from './metroMiddleware';
+import { checkSentryExpoNativeProject } from './sentryExpoNativeCheck';
 import {
   setSentryBabelTransformerOptions,
   setSentryDefaultBabelTransformerPathEnv,
@@ -114,6 +115,8 @@ export function getSentryExpoConfig(
 ): MetroConfig {
   setSentryMetroDevServerEnvFlag();
 
+  checkSentryExpoNativeProject(projectRoot);
+
   const getDefaultConfig = options.getDefaultConfig || loadExpoMetroConfigModule().getDefaultConfig;
   const config = getDefaultConfig(projectRoot, {
     ...options,

packages/core/src/js/tools/sentryExpoNativeCheck.ts

@@ -0,0 +1,89 @@
+import * as fs from 'fs';
+import * as path from 'path';
+
+const PREFIX = '[@sentry/react-native/expo]';
+
+/**
+ * Checks if prebuilt native projects (ios/android) have been configured with Sentry.
+ * If native directories exist but are missing Sentry configuration, warns the user
+ * to run `npx expo prebuild --clean`.
+ *
+ * This only runs for Expo projects (detected by the presence of `expo` in package.json dependencies).
+ */
+export function checkSentryExpoNativeProject(projectRoot: string): void {
+  try {
+    if (!isExpoProject(projectRoot)) {
+      return;
+    }
+
+    const missingPlatforms: string[] = [];
+
+    if (isIOSProjectMissingSentry(projectRoot)) {
+      missingPlatforms.push('iOS');
+    }
+
+    if (isAndroidProjectMissingSentry(projectRoot)) {
+      missingPlatforms.push('Android');
+    }
+
+    if (missingPlatforms.length > 0) {
+      const platforms = missingPlatforms.join(' and ');
+      // oxlint-disable-next-line eslint(no-console)
+      console.warn(
+        `${PREFIX} Sentry native configuration is missing from your prebuilt ${platforms} project.
+Run \`npx expo prebuild --clean\` to apply the Sentry Expo Plugin changes.
+Without this, source maps upload and native crash reporting may not work correctly.`,
+      );
+    }
+  } catch (_) {
+    // Never crash Metro startup — silently ignore any errors
+  }
+}
+
+function isExpoProject(projectRoot: string): boolean {
+  const packageJsonPath = path.resolve(projectRoot, 'package.json');
+  if (!fs.existsSync(packageJsonPath)) {
+    return false;
+  }
+
+  const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8'));
+  return !!(packageJson.dependencies?.expo || packageJson.devDependencies?.expo);
+}
+
+function isIOSProjectMissingSentry(projectRoot: string): boolean {
+  const iosDir = path.resolve(projectRoot, 'ios');
+  if (!fs.existsSync(iosDir)) {
+    return false;
+  }
+
+  const pbxprojPath = findPbxprojFile(iosDir);
+  if (!pbxprojPath) {
+    return false;
+  }
+
+  const pbxprojContents = fs.readFileSync(pbxprojPath, 'utf8');
+  return !pbxprojContents.includes('sentry-xcode') && !pbxprojContents.includes('Upload Debug Symbols to Sentry');
+}
+
+function isAndroidProjectMissingSentry(projectRoot: string): boolean {
+  const buildGradlePath = path.resolve(projectRoot, 'android', 'app', 'build.gradle');
+  if (!fs.existsSync(buildGradlePath)) {
+    return false;
+  }
+
+  const buildGradleContents = fs.readFileSync(buildGradlePath, 'utf8');
+  return !buildGradleContents.includes('sentry.gradle');
+}
+
+function findPbxprojFile(iosDir: string): string | null {
+  const entries = fs.readdirSync(iosDir);
+  for (const entry of entries) {
+    if (entry.endsWith('.xcodeproj')) {
+      const pbxprojPath = path.resolve(iosDir, entry, 'project.pbxproj');
+      if (fs.existsSync(pbxprojPath)) {
+        return pbxprojPath;
+      }
+    }
+  }
+  return null;
+}