Fix Buck2 --out permission errors on macOS for claude code (#55736)

Summary:
Pull Request resolved: #55736

changelog: [internal]

On macOS with EdenFS backed directories, Buck2's --out flag fails with "Operation not permitted" error.

This fix works around the issue by:
1. Building to a temp directory outside the repo (os.tmpdir())
2. Removing extended attributes with `xattr -rc` on macOS

Reviewed By: cipolleschi

Differential Revision: D92078500

fbshipit-source-id: 437734c068e4bf20a4f8e570e1184565810154d3

Author: sammy-SC

private/react-native-fantom/runner/executables/hermesc.js

@@ -21,6 +21,7 @@ import {
   runCommandSync,
 } from '../utils';
 import fs from 'fs';
+import os from 'os';
 import path from 'path';
 
 type TesterOptions = Readonly<{
@@ -44,7 +45,13 @@ export function build(options: TesterOptions): void {
     return;
   }
 
-  const tmpPath = destPath + '-' + Date.now();
+  // Use system temp directory outside the repo to avoid macOS extended
+  // attribute issues with EdenFS/NFS-backed directories
+  const tmpPath = path.join(
+    os.tmpdir(),
+    `hermesc-${Date.now()}-${process.pid}`,
+  );
+  const destTmpPath = destPath + '-' + Date.now() + '-' + process.pid;
 
   try {
     const result = runBuck2Sync([
@@ -65,11 +72,33 @@ export function build(options: TesterOptions): void {
       return;
     }
 
-    fs.renameSync(tmpPath, destPath);
+    // Remove extended attributes to avoid "Operation not permitted" errors
+    // when copying to EdenFS/NFS-backed directories on macOS
+    if (os.platform() === 'darwin') {
+      runCommandSync('xattr', ['-rc', tmpPath]);
+    }
+
+    fs.copyFileSync(tmpPath, destTmpPath);
+
+    try {
+      fs.renameSync(destTmpPath, destPath);
+    } catch (e: unknown) {
+      // Another process may have created the file already - that's fine
+      const code =
+        typeof e === 'object' && e != null && typeof e.code === 'string'
+          ? e.code
+          : null;
+      if (code !== 'EEXIST' && !fs.existsSync(destPath)) {
+        throw e;
+      }
+    }
   } finally {
     try {
       fs.unlinkSync(tmpPath);
     } catch {}
+    try {
+      fs.unlinkSync(destTmpPath);
+    } catch {}
   }
 }
 

private/react-native-fantom/runner/executables/tester.js

@@ -19,8 +19,10 @@ import {
   runBuck2,
   runBuck2Sync,
   runCommand,
+  runCommandSync,
 } from '../utils';
 import fs from 'fs';
+import os from 'os';
 import path from 'path';
 
 const FANTOM_TESTER_BUCK_TARGET =
@@ -47,7 +49,13 @@ export function build(options: TesterOptions): void {
     return;
   }
 
-  const tmpPath = destPath + '-' + Date.now();
+  // Use system temp directory outside the repo to avoid macOS extended
+  // attribute issues with EdenFS/NFS-backed directories
+  const tmpPath = path.join(
+    os.tmpdir(),
+    `fantom-tester-${Date.now()}-${process.pid}`,
+  );
+  const destTmpPath = destPath + '-' + Date.now() + '-' + process.pid;
 
   try {
     const result = runBuck2Sync([
@@ -68,11 +76,33 @@ export function build(options: TesterOptions): void {
       return;
     }
 
-    fs.renameSync(tmpPath, destPath);
+    // Remove extended attributes to avoid "Operation not permitted" errors
+    // when copying to EdenFS/NFS-backed directories on macOS
+    if (os.platform() === 'darwin') {
+      runCommandSync('xattr', ['-rc', tmpPath]);
+    }
+
+    fs.copyFileSync(tmpPath, destTmpPath);
+
+    try {
+      fs.renameSync(destTmpPath, destPath);
+    } catch (e: unknown) {
+      // Another process may have created the file already - that's fine
+      const code =
+        typeof e === 'object' && e != null && typeof e.code === 'string'
+          ? e.code
+          : null;
+      if (code !== 'EEXIST' && !fs.existsSync(destPath)) {
+        throw e;
+      }
+    }
   } finally {
     try {
       fs.unlinkSync(tmpPath);
     } catch {}
+    try {
+      fs.unlinkSync(destTmpPath);
+    } catch {}
   }
 }