fix(core): Lazy-load Metro internal modules to prevent Expo 55 import errors

CHANGELOG.md

@@ -12,6 +12,10 @@
 
 - Enable "Open Sentry" button in Playground for Expo apps ([#5947](https://github.com/getsentry/sentry-react-native/pull/5947))
 
+### Fixes
+
+- Lazy-load Metro internal modules to prevent Expo 55 import errors ([#5958](https://github.com/getsentry/sentry-react-native/pull/5958))
+
 ## 8.7.0
 
 ### Features

packages/core/src/js/tools/vendor/metro/utils.ts

@@ -32,48 +32,9 @@ import type * as bundleToStringType from 'metro/private/lib/bundleToString';
 
 import type { MetroSerializer } from '../../utils';
 
-// oxlint-disable-next-line typescript-eslint(no-explicit-any)
-let baseJSBundleModule: any;
-try {
-  baseJSBundleModule = require('metro/private/DeltaBundler/Serializers/baseJSBundle');
-} catch {
-  baseJSBundleModule = require('metro/src/DeltaBundler/Serializers/baseJSBundle');
-}
-
-const baseJSBundle: typeof baseJSBundleType =
-  typeof baseJSBundleModule === 'function'
-    ? baseJSBundleModule
-    : (baseJSBundleModule?.baseJSBundle ?? baseJSBundleModule?.default);
-
-let sourceMapString: typeof sourceMapStringType;
-try {
-  const sourceMapStringModule = require('metro/private/DeltaBundler/Serializers/sourceMapString');
-  sourceMapString = (sourceMapStringModule as { sourceMapString: typeof sourceMapStringType }).sourceMapString;
-} catch (e) {
-  sourceMapString = require('metro/src/DeltaBundler/Serializers/sourceMapString');
-  if ('sourceMapString' in sourceMapString) {
-    // Changed to named export in https://github.com/facebook/metro/commit/34148e61200a508923315fbe387b26d1da27bf4b
-    // Metro 0.81.0 and 0.80.10 patch
-    sourceMapString = (sourceMapString as { sourceMapString: typeof sourceMapStringType }).sourceMapString;
-  }
-}
-
-// oxlint-disable-next-line typescript-eslint(no-explicit-any)
-let bundleToStringModule: any;
-try {
-  bundleToStringModule = require('metro/private/lib/bundleToString');
-} catch {
-  bundleToStringModule = require('metro/src/lib/bundleToString');
-}
-
-const bundleToString: typeof bundleToStringType =
-  typeof bundleToStringModule === 'function'
-    ? bundleToStringModule
-    : (bundleToStringModule?.bundleToString ?? bundleToStringModule?.default);
-
 type NewSourceMapStringExport = {
   // Since Metro v0.80.10 https://github.com/facebook/metro/compare/v0.80.9...v0.80.10#diff-1b836d1729e527a725305eef0cec22e44605af2700fa413f4c2489ea1a03aebcL28
-  sourceMapString: typeof sourceMapString;
+  sourceMapString: typeof sourceMapStringType;
 };
 
 /**
@@ -108,6 +69,49 @@ export const getSortedModules = (
  * https://github.com/facebook/metro/blob/9b85f83c9cc837d8cd897aa7723be7da5b296067/packages/metro/src/Server.js#L244-L277
  */
 export const createDefaultMetroSerializer = (): MetroSerializer => {
+  // Lazy-load Metro internals only when serializer is created
+  // This defers requiring Metro modules until they're actually needed (during build),
+  // avoiding import-time failures when Metro is only a transitive dependency
+
+  // oxlint-disable-next-line typescript-eslint(no-explicit-any)
+  let baseJSBundleModule: any;
+  try {
+    baseJSBundleModule = require('metro/private/DeltaBundler/Serializers/baseJSBundle');
+  } catch {
+    baseJSBundleModule = require('metro/src/DeltaBundler/Serializers/baseJSBundle');
+  }
+
+  const baseJSBundle: typeof baseJSBundleType =
+    typeof baseJSBundleModule === 'function'
+      ? baseJSBundleModule
+      : (baseJSBundleModule?.baseJSBundle ?? baseJSBundleModule?.default);
+
+  let sourceMapString: typeof sourceMapStringType;
+  try {
+    const sourceMapStringModule = require('metro/private/DeltaBundler/Serializers/sourceMapString');
+    sourceMapString = (sourceMapStringModule as { sourceMapString: typeof sourceMapStringType }).sourceMapString;
+  } catch (e) {
+    sourceMapString = require('metro/src/DeltaBundler/Serializers/sourceMapString');
+    if ('sourceMapString' in sourceMapString) {
+      // Changed to named export in https://github.com/facebook/metro/commit/34148e61200a508923315fbe387b26d1da27bf4b
+      // Metro 0.81.0 and 0.80.10 patch
+      sourceMapString = (sourceMapString as { sourceMapString: typeof sourceMapStringType }).sourceMapString;
+    }
+  }
+
+  // oxlint-disable-next-line typescript-eslint(no-explicit-any)
+  let bundleToStringModule: any;
+  try {
+    bundleToStringModule = require('metro/private/lib/bundleToString');
+  } catch {
+    bundleToStringModule = require('metro/src/lib/bundleToString');
+  }
+
+  const bundleToString: typeof bundleToStringType =
+    typeof bundleToStringModule === 'function'
+      ? bundleToStringModule
+      : (bundleToStringModule?.bundleToString ?? bundleToStringModule?.default);
+
   return (entryPoint, preModules, graph, options) => {
     // baseJSBundle assigns IDs to modules in a consistent order
     let bundle = baseJSBundle(entryPoint, preModules, graph, options);

packages/core/test/tools/sentryMetroSerializer.test.ts

@@ -232,6 +232,33 @@ describe('Sentry Metro Serializer', () => {
       expect(debugId).toMatch(/^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$/);
     });
   });
+
+  test('createDefaultMetroSerializer can be created without Metro internals being loaded at import time', () => {
+    // This test verifies that the lazy-loading of Metro internals works correctly.
+    // The createDefaultMetroSerializer function should be callable without triggering
+    // module-level requires of Metro internals at import time.
+    // See: https://github.com/getsentry/sentry-react-native/issues/5957
+
+    // Import the function
+    const { createDefaultMetroSerializer: createSerializer } = require('../../src/js/tools/vendor/metro/utils');
+
+    // Create the serializer - this should succeed without loading Metro internals
+    const serializer = createSerializer();
+    expect(typeof serializer).toBe('function');
+
+    // Verify the serializer can be invoked with proper arguments and produces output
+    const [entryPoint, preModules, graph, options] = mockMinSerializerArgs();
+    const result = serializer(entryPoint, preModules, graph, options);
+
+    expect(result).toHaveProperty('code');
+    expect(result).toHaveProperty('map');
+    expect(typeof result.code).toBe('string');
+    expect(typeof result.map).toBe('string');
+    // Both code and map should exist (even if minimal for empty bundle)
+    expect(result.code).toBeDefined();
+    expect(result.map).toBeDefined();
+    //    }
+  });
 });
 
 function mockMinSerializerArgs(options?: {