From 02133dc97e28023f9f973c6f8ac2234521737ada Mon Sep 17 00:00:00 2001
From: weili <541602953@qq.com>
Date: Fri, 12 Jun 2026 06:07:58 +0000
Subject: [PATCH] xargs: do not panic on empty input in replace mode

In replace mode (-I/-i/--replace) xargs runs the command once per input item, so
with empty input it should run nothing. Instead the final builder was still
executed and `CommandBuilder::execute` indexed `extra_args[0]`, which is empty
for no input, panicking with index-out-of-bounds. Treat replace mode as implying
--no-run-if-empty (as GNU does) so empty input runs nothing and exits 0.
---
 src/xargs/mod.rs    | 2 +-
 tests/test_xargs.rs | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/xargs/mod.rs b/src/xargs/mod.rs
index cf3638df..9679a05a 100644
--- a/src/xargs/mod.rs
+++ b/src/xargs/mod.rs
@@ -1159,7 +1159,7 @@ fn do_xargs(args: &[&str]) -> Result<CommandResult, XargsError> {
             options.exit_if_pass_char_limit,
             options.max_args,
             options.max_lines,
-            options.no_run_if_empty,
+            options.no_run_if_empty || options.replace.is_some(),
         ),
     )?;
     Ok(result)
diff --git a/tests/test_xargs.rs b/tests/test_xargs.rs
index 3faa0421..3bbe17f2 100644
--- a/tests/test_xargs.rs
+++ b/tests/test_xargs.rs
@@ -73,6 +73,15 @@ fn xargs_if_empty() {
     ucmd().args(&["--no-run-if-empty"]).succeeds().no_output();
 }
 
+#[test]
+fn xargs_replace_empty_input() {
+    ucmd()
+        .args(&["-I", "{}", "echo", "hello", "{}"])
+        .succeeds()
+        .no_output();
+    ucmd().args(&["-i", "echo", "{}"]).succeeds().no_output();
+}
+
 #[test]
 fn xargs_max_args() {
     ucmd()