⚡ Bolt: [performance improvement]

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2026-04-24 - Optimization: Direct encoding in fs.readFileSync
+**Learning:** In Node.js components of the codebase, avoid unnecessary intermediate memory allocations by passing the encoding string directly to fs.readFileSync (e.g., `fs.readFileSync(file, 'utf8')`) instead of calling `.toString()` on the resulting Buffer. This serves as a valid micro-optimization.
+**Action:** Replaced instances of `fs.readFileSync(...).toString()` with `fs.readFileSync(..., 'utf8')` and correctly updated type assertions (`as string`) in TypeScript tests utilizing memfs.

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') as string);
     expect(devices.length).toBe(1);
     expect(devices[0].installationId).toBe('test-device-id');
   });

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) {

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 {

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') as string).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') as string).toMatch('package xyz.bront.app');
+      expect(fs.readFileSync(nestedClassPath, 'utf8') as string).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') as string).toMatch('package = "xyz.bront.app"');
+      expect(fs.readFileSync(buckPath, 'utf8') as string).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') as string).toMatch('package com.bront');
     });
   });
 });

packages/@expo/prebuild-config/src/plugins/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') as string;
     contents = await setSplashScreenLegacyMainActivity(
       exp,
       { backgroundColor: '#000020', resizeMode: 'native' },