fix: apply suggestions

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: reubeno

brush-core/src/commands.rs

@@ -724,8 +724,9 @@ pub(crate) async fn invoke_shell_function(
     )?;
 
     // A function executes within the current shell process and shares its caller's open files,
-    // so the parameters are passed through by shared reference rather than cloned. The shared
-    // borrow also guarantees the body cannot disturb the caller's open-file table.
+    // so the parameters are passed through by shared reference rather than cloned. This prevents
+    // direct mutation of the caller's `ExecutionParameters` open-file table, though the function
+    // may still change the shell's persistent open files via builtins (e.g. `exec`).
     let result = body.execute(context.shell, &context.params).await;
 
     // We've come back out, reflect it.

brush-core/src/interp.rs

@@ -1777,7 +1777,7 @@ pub(crate) async fn setup_redirect(
                             .parse::<ShellFd>()
                             .map_err(|_| error::ErrorKind::InvalidRedirection)?;
 
-                        // Duplicate the fd.
+                        // Reference the same open file as the source fd (shared handle; no OS-level duplication).
                         let Some(target_file) = params.try_fd(shell, source_fd_num) else {
                             return Err(error::ErrorKind::BadFileDescriptor(source_fd_num).into());
                         };

brush-shell/tests/cases/compat/fd_management.yaml

@@ -25,7 +25,7 @@ cases:
     args:
       - "-c"
       - |
-        ulimit -n 256
+        ulimit -n 256 || exit 1
         emit() {
           local v
           v=$(echo "$1")
@@ -41,7 +41,7 @@ cases:
     args:
       - "-c"
       - |
-        ulimit -n 256
+        ulimit -n 256 || exit 1
         work() {
           local v
           v=$(echo "alias-$1" 2>/dev/null)
@@ -57,7 +57,7 @@ cases:
     args:
       - "-c"
       - |
-        ulimit -n 256
+        ulimit -n 256 || exit 1
         rec() {
           local n=$1
           if [ "$n" -le 0 ]; then