⚡ Bolt: [performance improvement] avoid Buffer allocation in fs.readFileSync calls

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2026-04-30 - Refactored fs.readFileSync calls
+**Learning:** Calling `.toString()` on the Buffer returned by `fs.readFileSync(path)` causes unnecessary intermediate memory allocations and string conversion overhead. Passing the encoding directly as `fs.readFileSync(path, 'utf8')` is faster and more memory efficient.
+**Action:** Always prefer `fs.readFileSync(path, 'utf8')` over chaining `.toString()` in Node.js scripts.

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');
   });

packages/@expo/cli/src/utils/mergeGitIgnorePaths.ts

@@ -35,8 +35,9 @@ export function mergeGitIgnorePaths(
     return null;
   }
 
-  const targetGitIgnore = fs.readFileSync(targetGitIgnorePath).toString();
-  const sourceGitIgnore = fs.readFileSync(sourceGitIgnorePath).toString();
+  // Read using utf8 directly to avoid buffer allocation
+  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 +125,8 @@ 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();
+        // Read using utf8 directly to avoid buffer allocation
+        let contents = fs.readFileSync(filepath, 'utf8');
         contents = contents.replace(
           new RegExp(transformJavaClassDescriptor(currentPackageName).replace(/\//g, '\\/'), 'g'),
           transformJavaClassDescriptor(packageName)
@@ -207,7 +208,8 @@ export async function renamePackageOnDiskForType({
   filesToUpdate.forEach((filepath: string) => {
     try {
       if (fs.lstatSync(filepath).isFile()) {
-        let contents = fs.readFileSync(filepath).toString();
+        // Read using utf8 directly to avoid buffer allocation
+        let contents = fs.readFileSync(filepath, 'utf8');
         if (path.extname(filepath) === '.kt') {
           contents = replacePackageName(contents, currentPackageName, kotlinSanitizedPackageName);
         } else {