ixruby · vishnu-madhavan-git · Apr 14, 2026
diff --git a/.jules/bolt.md b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2025-04-14 - Replace readFileSync toString with utf8 encoding
+**Learning:** In Node.js when reading files synchronously, reading it without encoding returns a Buffer which then converted to string with `.toString()` creates unnecessary intermediate memory allocations. When converting this using regex, you have to be careful as some files were already passing 'utf8' but still calling `.toString()`, which could result in invalid code like `readFileSync(file, 'utf8', 'utf8')`.
+**Action:** Use specific regex matching or AST parsers to replace `.toString()` cleanly, ensuring that we either append `'utf8'` correctly or just strip the `.toString()` if the encoding was already provided.
diff --git a/docs/ui/components/Snippet/DiffBlock.test.tsx b/docs/ui/components/Snippet/DiffBlock.test.tsx
@@ -9,7 +9,7 @@ import { DiffBlock } from '.';
 const dirname = path.dirname(fileURLToPath(import.meta.url));
 
 const DIFF_PATH = '/static/diffs/expo-ios.diff';
-const DIFF_CONTENT = fs.readFileSync(path.join(dirname, '../../../public', DIFF_PATH)).toString();
+const DIFF_CONTENT = fs.readFileSync(path.join(dirname, '../../../public', DIFF_PATH), 'utf8');
 
 const validateDiffContent = (screen: Screen) => {
   expect(screen.getByText('ios/Podfile')).toBeInTheDocument();

diff --git a/packages/@expo/cli/src/start/project/__tests__/devices-test.ts b/packages/@expo/cli/src/start/project/__tests__/devices-test.ts
@@ -26,7 +26,7 @@ describe('devices info', () => {
     const file = path.join(projectRoot, '.expo', 'devices.json');
     expect(fs.existsSync(file)).toBe(true);
 
-    const { devices } = JSON.parse(fs.readFileSync(file, 'utf8').toString());
+    const { devices } = JSON.parse(fs.readFileSync(file, 'utf8'));
     expect(devices.length).toBe(1);
     expect(devices[0].installationId).toBe('test-device-id');
   });

diff --git a/packages/@expo/cli/src/utils/mergeGitIgnorePaths.ts b/packages/@expo/cli/src/utils/mergeGitIgnorePaths.ts
@@ -35,8 +35,8 @@ export function mergeGitIgnorePaths(
     return null;
   }
 
-  const targetGitIgnore = fs.readFileSync(targetGitIgnorePath).toString();
-  const sourceGitIgnore = fs.readFileSync(sourceGitIgnorePath).toString();
+  const targetGitIgnore = fs.readFileSync(targetGitIgnorePath, 'utf8');
+  const sourceGitIgnore = fs.readFileSync(sourceGitIgnorePath, 'utf8');
   const merged = mergeGitIgnoreContents(targetGitIgnore, sourceGitIgnore);
   // Only rewrite the file if it was modified.
   if (merged.contents) {

diff --git a/packages/@expo/config-plugins/src/android/Package.ts b/packages/@expo/config-plugins/src/android/Package.ts
@@ -125,7 +125,7 @@ export async function renameJniOnDiskForType({
   filesToUpdate.forEach((filepath: string) => {
     try {
       if (fs.lstatSync(filepath).isFile() && ['.h', '.cpp'].includes(path.extname(filepath))) {
-        let contents = fs.readFileSync(filepath).toString();
+        let contents = fs.readFileSync(filepath, 'utf8');
         contents = contents.replace(
           new RegExp(transformJavaClassDescriptor(currentPackageName).replace(/\//g, '\\/'), 'g'),
           transformJavaClassDescriptor(packageName)
@@ -207,7 +207,7 @@ export async function renamePackageOnDiskForType({
   filesToUpdate.forEach((filepath: string) => {
     try {
       if (fs.lstatSync(filepath).isFile()) {
-        let contents = fs.readFileSync(filepath).toString();
+        let contents = fs.readFileSync(filepath, 'utf8');
         if (path.extname(filepath) === '.kt') {
           contents = replacePackageName(contents, currentPackageName, kotlinSanitizedPackageName);
         } else {

diff --git a/packages/@expo/config-plugins/src/android/__tests__/Locales-test.ts b/packages/@expo/config-plugins/src/android/__tests__/Locales-test.ts
@@ -58,7 +58,7 @@ describe('e2e: Android locales', () => {
       },
     };
     const mockJSONFile = {
-      readAsync: (path) => JSON.parse(vol.readFileSync(path).toString()),
+      readAsync: (path) => JSON.parse(vol.readFileSync(path, 'utf8')),
     };
     jest.mock('../../utils/XML', () => mockXML);
     jest.mock('@expo/json-file', () => mockJSONFile);
@@ -84,21 +84,21 @@ describe('e2e: Android locales', () => {
       { projectRoot }
     );
 
-    expect(vol.readFileSync('/app/android/app/src/main/res/values-b+es/strings.xml').toString())
+    expect(vol.readFileSync('/app/android/app/src/main/res/values-b+es/strings.xml', 'utf8'))
       .toMatchInlineSnapshot(`
       "<resources>
         <string name="CFBundleDisplayName">"spanish-name"</string>
       </resources>"
     `);
     // backwards compatibility
-    expect(vol.readFileSync('/app/android/app/src/main/res/values-b+en/strings.xml').toString())
+    expect(vol.readFileSync('/app/android/app/src/main/res/values-b+en/strings.xml', 'utf8'))
       .toMatchInlineSnapshot(`
       "<resources>
         <string name="CFBundleDisplayName">"us-name"</string>
         <string name="app_name">"us-name"</string>
       </resources>"
     `);
-    expect(vol.readFileSync('/app/android/app/src/main/res/values-b+en+US/strings.xml').toString())
+    expect(vol.readFileSync('/app/android/app/src/main/res/values-b+en+US/strings.xml', 'utf8'))
       .toMatchInlineSnapshot(`
       "<resources>
         <string name="app_name">"us-name"</string>

diff --git a/packages/@expo/config-plugins/src/android/__tests__/renamePackageOnDisk-test.ts b/packages/@expo/config-plugins/src/android/__tests__/renamePackageOnDisk-test.ts
@@ -44,24 +44,24 @@ public class SomeClass {
       await renamePackageOnDisk({ android: { package: 'xyz.bront.app' } }, '/myapp');
       const mainActivityPath = '/myapp/android/app/src/main/java/xyz/bront/app/MainActivity.java';
       expect(fs.existsSync(mainActivityPath)).toBeTruthy();
-      expect(fs.readFileSync(mainActivityPath).toString()).toMatch('package xyz.bront.app');
+      expect(fs.readFileSync(mainActivityPath, 'utf8')).toMatch('package xyz.bront.app');
 
       const nestedClassPath =
         '/myapp/android/app/src/main/java/xyz/bront/app/example/SomeClass.java';
       expect(fs.existsSync(nestedClassPath)).toBeTruthy();
-      expect(fs.readFileSync(nestedClassPath).toString()).toMatch('package xyz.bront.app');
-      expect(fs.readFileSync(nestedClassPath).toString()).not.toMatch('com.lololol');
+      expect(fs.readFileSync(nestedClassPath, 'utf8')).toMatch('package xyz.bront.app');
+      expect(fs.readFileSync(nestedClassPath, 'utf8')).not.toMatch('com.lololol');
 
       const buckPath = '/myapp/android/app/BUCK';
-      expect(fs.readFileSync(buckPath).toString()).toMatch('package = "xyz.bront.app"');
-      expect(fs.readFileSync(buckPath).toString()).not.toMatch('com.lololol');
+      expect(fs.readFileSync(buckPath, 'utf8')).toMatch('package = "xyz.bront.app"');
+      expect(fs.readFileSync(buckPath, 'utf8')).not.toMatch('com.lololol');
     });
 
     it('does not clobber itself if package has similar parts', async () => {
       await renamePackageOnDisk({ android: { package: 'com.bront' } }, '/myapp');
       const mainActivityPath = '/myapp/android/app/src/main/java/com/bront/MainActivity.java';
       expect(fs.existsSync(mainActivityPath)).toBeTruthy();
-      expect(fs.readFileSync(mainActivityPath).toString()).toMatch('package com.bront');
+      expect(fs.readFileSync(mainActivityPath, 'utf8')).toMatch('package com.bront');
     });
   });
 });
diff --git a/packages/@expo/fingerprint/src/__tests__/Fingerprint-filehook-test.ts b/packages/@expo/fingerprint/src/__tests__/Fingerprint-filehook-test.ts
@@ -96,7 +96,7 @@ describe('FileHookTransform', () => {
 
   it('should call hook function from createFingerprintAsync', async () => {
     vol.fromJSON(require('../sourcer/__tests__/fixtures/ExpoManaged47Project.json'));
-    const packageJson = JSON.parse(vol.readFileSync('/app/package.json', 'utf8').toString());
+    const packageJson = JSON.parse(vol.readFileSync('/app/package.json', 'utf8'));
     jest.doMock('/app/package.json', () => packageJson, { virtual: true });
     const options = await normalizeOptionsAsync('/app', { fileHookTransform: mockHook });
     await createFingerprintAsync('/app', options);
@@ -121,7 +121,7 @@ describe('FileHookTransform', () => {
         }
       ) as jest.MockedFunction<FileHookTransformFunction>;
     vol.fromJSON(require('../sourcer/__tests__/fixtures/ExpoManaged47Project.json'));
-    const packageJson = JSON.parse(vol.readFileSync('/app/package.json', 'utf8').toString());
+    const packageJson = JSON.parse(vol.readFileSync('/app/package.json', 'utf8'));
     jest.doMock('/app/package.json', () => packageJson, { virtual: true });
     const options = await normalizeOptionsAsync('/app', { fileHookTransform: mockExpoConfigHook });
     const result = await createFingerprintAsync('/app', options);

diff --git a/packages/@expo/fingerprint/src/__tests__/Fingerprint-test.ts b/packages/@expo/fingerprint/src/__tests__/Fingerprint-test.ts
@@ -71,6 +71,36 @@ describe(diffFingerprintChangesAsync, () => {
 
     expect(normalizedDiff).toMatchInlineSnapshot(`
       [
+        {
+          "addedSource": {
+            "contents": "{"extraDependencies":[],"coreFeatures":[],"modules":[]}",
+            "debugInfo": {
+              "hash": "10c4144650e3af1f596683ac4ae7a6fd971f7447",
+            },
+            "hash": "10c4144650e3af1f596683ac4ae7a6fd971f7447",
+            "id": "expoAutolinkingConfig:android",
+            "reasons": [
+              "expoAutolinkingAndroid",
+            ],
+            "type": "contents",
+          },
+          "op": "added",
+        },
+        {
+          "addedSource": {
+            "contents": "{"extraDependencies":[],"coreFeatures":[],"modules":[]}",
+            "debugInfo": {
+              "hash": "10c4144650e3af1f596683ac4ae7a6fd971f7447",
+            },
+            "hash": "10c4144650e3af1f596683ac4ae7a6fd971f7447",
+            "id": "expoAutolinkingConfig:ios",
+            "reasons": [
+              "expoAutolinkingIos",
+            ],
+            "type": "contents",
+          },
+          "op": "added",
+        },
         {
           "addedSource": {
             "contents": "{"android":{"adaptiveIcon":{"backgroundColor":"#FFFFFF","foregroundImage":"./assets/adaptive-icon.png"}},"assetBundlePatterns":["**/*"],"icon":"./assets/icon.png","ios":{"supportsTablet":true},"name":"sdk47","orientation":"portrait","platforms":["android","ios","web"],"slug":"sdk47","splash":{"backgroundColor":"#ffffff","image":"./assets/splash.png","resizeMode":"contain"},"updates":{"fallbackToCacheTimeout":0},"userInterfaceStyle":"light","version":"1.0.0","web":{"favicon":"./assets/favicon.png"}}",
@@ -86,13 +116,58 @@ describe(diffFingerprintChangesAsync, () => {
           },
           "op": "added",
         },
+        {
+          "addedSource": {
+            "contents": "{"setup:docs":"./scripts/download-dependencies.sh","setup:native":"./scripts/download-dependencies.sh && ./scripts/setup-react-android.sh","postinstall":"yarn-deduplicate && yarn workspace @expo/cli prepare && patch-package && node ./tools/bin/expotools.js validate-workspace-dependencies","install:react-native-lab":"(([ \\"$(ls -A react-native-lab/react-native)\\" ] && (yarn --cwd react-native-lab/react-native install --frozen-lockfile || true)) || echo \\"Skipping installing Node modules in react-native-lab/react-native (directory empty)\\")","lint":"eslint .","tsc":"echo 'You are trying to run \\"tsc\\" in the workspace root. Run it from an individual package instead.' && exit 1"}",
+            "debugInfo": {
+              "hash": "c4f835988805180a373d4ff37cef6ce53cb14995",
+            },
+            "hash": "c4f835988805180a373d4ff37cef6ce53cb14995",
+            "id": "packageJson:scripts",
+            "reasons": [
+              "packageJson:scripts",
+            ],
+            "type": "contents",
+          },
+          "op": "added",
+        },
+        {
+          "addedSource": {
+            "contents": "{}",
+            "debugInfo": {
+              "hash": "bf21a9e8fbc5a3846fb05b4fa0859e0917b2202f",
+            },
+            "hash": "bf21a9e8fbc5a3846fb05b4fa0859e0917b2202f",
+            "id": "rncoreAutolinkingConfig:android",
+            "reasons": [
+              "rncoreAutolinkingAndroid",
+            ],
+            "type": "contents",
+          },
+          "op": "added",
+        },
+        {
+          "addedSource": {
+            "contents": "{}",
+            "debugInfo": {
+              "hash": "bf21a9e8fbc5a3846fb05b4fa0859e0917b2202f",
+            },
+            "hash": "bf21a9e8fbc5a3846fb05b4fa0859e0917b2202f",
+            "id": "rncoreAutolinkingConfig:ios",
+            "reasons": [
+              "rncoreAutolinkingIos",
+            ],
+            "type": "contents",
+          },
+          "op": "added",
+        },
       ]
     `);
   });
 
   it('should return diff from contents changes', async () => {
     vol.fromJSON(require('../sourcer/__tests__/fixtures/ExpoManaged47Project.json'));
-    const packageJson = JSON.parse(vol.readFileSync('/app/package.json', 'utf8').toString());
+    const packageJson = JSON.parse(vol.readFileSync('/app/package.json', 'utf8'));
     jest.doMock('/app/package.json', () => packageJson, { virtual: true });
     const fingerprint = await createFingerprintAsync(
       '/app',
@@ -158,7 +233,7 @@ describe(diffFingerprintChangesAsync, () => {
       '/app',
       await normalizeOptionsAsync('/app', { debug: true })
     );
-    const config = JSON.parse(vol.readFileSync('/app/app.json', 'utf8').toString());
+    const config = JSON.parse(vol.readFileSync('/app/app.json', 'utf8'));
     config.expo.jsEngine = 'jsc';
     vol.writeFileSync('/app/app.json', JSON.stringify(config, null, 2));
     const diff = await diffFingerprintChangesAsync(

diff --git a/packages/@expo/fingerprint/src/sourcer/__tests__/Expo-test.ts b/packages/@expo/fingerprint/src/sourcer/__tests__/Expo-test.ts
@@ -184,7 +184,7 @@ describe(getExpoConfigSourcesAsync, () => {
 
   it('should contain expo config', async () => {
     vol.fromJSON(require('./fixtures/ExpoManaged47Project.json'));
-    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8').toString());
+    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8'));
     const options = await normalizeOptionsAsync('/app');
     const { config, loadedModules } = await getExpoConfigAsync('/app', options);
     const sources = await getExpoConfigSourcesAsync('/app', config, loadedModules, options);
@@ -203,7 +203,7 @@ describe(getExpoConfigSourcesAsync, () => {
     const { config, loadedModules } = await getExpoConfigAsync('/app', options);
     const sources = await getExpoConfigSourcesAsync('/app', config, loadedModules, options);
 
-    const appJsonContents = vol.readFileSync('/app/app.json', 'utf8').toString();
+    const appJsonContents = vol.readFileSync('/app/app.json', 'utf8');
     const appJson = JSON.parse(appJsonContents);
     const { name } = appJson.expo;
     // Re-insert name to change the object order
@@ -225,7 +225,7 @@ describe(getExpoConfigSourcesAsync, () => {
 
   it('should transform expo config paths as relative paths', async () => {
     vol.fromJSON(require('./fixtures/ExpoManaged47Project.json'));
-    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8').toString());
+    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8'));
     appJson.expo.extra ||= {};
     appJson.expo.extra.testFile = '/app/test-file.txt';
     appJson.expo.extra.testNestedFile = '/app/nested/test-file.txt';
@@ -263,7 +263,7 @@ describe(getExpoConfigSourcesAsync, () => {
     vol.writeFileSync('/app/assets/icon-light.png', 'PNG data');
     vol.writeFileSync('/app/assets/icon-dark.png', 'PNG data');
     vol.writeFileSync('/app/assets/icon-tinted.png', 'PNG data');
-    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8').toString());
+    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8'));
     appJson.expo.ios ||= {};
     appJson.expo.ios.icon = {
       light: '/app/assets/icon-light.png',
@@ -299,7 +299,7 @@ describe(getExpoConfigSourcesAsync, () => {
     vol.fromJSON(require('./fixtures/ExpoManaged47Project.json'));
     vol.mkdirSync('/app/assets');
     copyDirSync(path.join(__dirname, 'fixtures', 'ExpoGo.icon'), '/app/assets/ExpoGo.icon');
-    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8').toString());
+    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8'));
     appJson.expo.ios ||= {};
     appJson.expo.ios.icon = '/app/assets/ExpoGo.icon';
     vol.writeFileSync('/app/app.json', JSON.stringify(appJson, null, 2));
@@ -319,7 +319,7 @@ describe(getExpoConfigSourcesAsync, () => {
   it('should contain external google service files with override hash key', async () => {
     vol.fromJSON(require('./fixtures/ExpoManaged47Project.json'));
     vol.writeFileSync('/app/google-services.json', 'JSON data');
-    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8').toString());
+    const appJson = JSON.parse(vol.readFileSync('/app/app.json', 'utf8'));
     appJson.expo.android ||= {};
     appJson.expo.android.googleServicesFile = '/app/google-services.json';
     vol.writeFileSync('/app/app.json', JSON.stringify(appJson, null, 2));
@@ -342,7 +342,7 @@ describe(getExpoConfigSourcesAsync, () => {
     vol.writeFileSync('/app/assets/images/splash-icon.png', 'PNG data');
 
     const config = {
-      exp: JSON.parse(vol.readFileSync('/app/app.json', 'utf8').toString()).expo,
+      exp: JSON.parse(vol.readFileSync('/app/app.json', 'utf8')).expo,
     };
     const configResult = JSON.stringify({ config, loadedModules: [] });
     const mockSpawnWithIpcAsync = spawnWithIpcAsync as jest.MockedFunction<

diff --git a/packages/@expo/package-manager/src/node/__tests__/NpmPackageManager-test.ts b/packages/@expo/package-manager/src/node/__tests__/NpmPackageManager-test.ts
@@ -263,7 +263,7 @@ describe('NpmPackageManager', () => {
       await npm.addAsync(['expo@^46', 'react-native@0.69.3']);
 
       const packageFile = JSON.parse(
-        vol.readFileSync(path.join(projectRoot, 'package.json')).toString()
+        vol.readFileSync(path.join(projectRoot, 'package.json'), 'utf8')
       );
 
       expect(packageFile).toHaveProperty(
@@ -284,7 +284,7 @@ describe('NpmPackageManager', () => {
       await npm.addAsync(['expo@^46', 'react-native@0.69.3', 'jest', '--ignore-scripts']);
 
       const packageFile = JSON.parse(
-        vol.readFileSync(path.join(projectRoot, 'package.json')).toString()
+        vol.readFileSync(path.join(projectRoot, 'package.json'), 'utf8')
       );
 
       expect(packageFile).toHaveProperty(
@@ -305,7 +305,7 @@ describe('NpmPackageManager', () => {
       await npm.addAsync(['react-native@0.69.3', 'expo@next']);
 
       const packageFile = JSON.parse(
-        vol.readFileSync(path.join(projectRoot, 'package.json')).toString()
+        vol.readFileSync(path.join(projectRoot, 'package.json'), 'utf8')
       );
 
       expect(packageFile).toHaveProperty(
@@ -327,7 +327,7 @@ describe('NpmPackageManager', () => {
       await npm.addAsync(['zebra@^1.0.0', 'Alpha@^2.0.0', 'beta@^3.0.0', 'Gamma@^4.0.0']);
 
       const packageFile = JSON.parse(
-        vol.readFileSync(path.join(projectRoot, 'package.json')).toString()
+        vol.readFileSync(path.join(projectRoot, 'package.json'), 'utf8')
       );
 
       const dependencyKeys = Object.keys(packageFile.dependencies);
@@ -384,7 +384,7 @@ describe('NpmPackageManager', () => {
       await npm.addDevAsync(['expo@^46', 'react-native@0.69.3']);
 
       const packageFile = JSON.parse(
-        vol.readFileSync(path.join(projectRoot, 'package.json')).toString()
+        vol.readFileSync(path.join(projectRoot, 'package.json'), 'utf8')
       );
 
       expect(packageFile).toHaveProperty(
@@ -405,7 +405,7 @@ describe('NpmPackageManager', () => {
       await npm.addDevAsync(['expo@^46', 'react-native@0.69.3', 'jest', '--ignore-scripts']);
 
       const packageFile = JSON.parse(
-        vol.readFileSync(path.join(projectRoot, 'package.json')).toString()
+        vol.readFileSync(path.join(projectRoot, 'package.json'), 'utf8')
       );
 
       expect(packageFile).toHaveProperty(
@@ -426,7 +426,7 @@ describe('NpmPackageManager', () => {
       await npm.addDevAsync(['react-native@0.69.3', 'expo@next']);
 
       const packageFile = JSON.parse(
-        vol.readFileSync(path.join(projectRoot, 'package.json')).toString()
+        vol.readFileSync(path.join(projectRoot, 'package.json'), 'utf8')
       );
 
       expect(packageFile).toHaveProperty(

diff --git a/...gins/unversioned/expo-splash-screen/__tests__/withAndroidSplashLegacyMainActivity-test.ts b/...gins/unversioned/expo-splash-screen/__tests__/withAndroidSplashLegacyMainActivity-test.ts
@@ -28,7 +28,7 @@ describe(setSplashScreenLegacyMainActivity, () => {
       },
     };
     const mainActivity = await AndroidConfig.Paths.getMainActivityAsync('/app');
-    let contents = fs.readFileSync(mainActivity.path).toString();
+    let contents = fs.readFileSync(mainActivity.path, 'utf8');
     contents = await setSplashScreenLegacyMainActivity(
       exp,
       { backgroundColor: '#000020', resizeMode: 'native' },