From 7d3b157f1316550adaf70a2a5eabd37d9be35288 Mon Sep 17 00:00:00 2001
From: Peter Ammon <rf@fishshell.com>
Date: Sat, 8 Mar 2025 20:26:03 -0800
Subject: [PATCH] Allow sprintf! macros to accept format string only

This allows something like `sprintf!("foo")`. Previously this was a compile time
error.

Fixes #11243
---
 printf/src/lib.rs   | 14 ++++++--------
 printf/src/tests.rs | 12 ++++++++++++
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/printf/src/lib.rs b/printf/src/lib.rs
index 6e9b7b581..733d7a193 100644
--- a/printf/src/lib.rs
+++ b/printf/src/lib.rs
@@ -32,13 +32,12 @@ macro_rules! sprintf {
     // Write to a newly allocated String, and return it.
     // This panics if the format string or arguments are invalid.
     (
-        $fmt:expr, // Format string, which should implement FormatString.
-        $($arg:expr),* // arguments
-        $(,)? // optional trailing comma
+        $fmt:expr // Format string, which should implement FormatString.
+        $(, $($arg:expr),*)? // arguments
     ) => {
         {
             let mut target = String::new();
-            $crate::sprintf!(=> &mut target, $fmt, $($arg),*);
+            $crate::sprintf!(=> &mut target, $fmt $(, $($arg),*)?);
             target
         }
     };
@@ -47,9 +46,8 @@ macro_rules! sprintf {
     // The target should implement std::fmt::Write.
     (
         => $target:expr, // target string
-        $fmt:expr, // format string
-        $($arg:expr),* // arguments
-        $(,)? // optional trailing comma
+        $fmt:expr // format string
+        $(, $($arg:expr),*)? // arguments
     ) => {
         {
             // May be no args!
@@ -58,7 +56,7 @@ macro_rules! sprintf {
             $crate::printf_c_locale(
                 $target,
                 $fmt,
-                &mut [$($arg.to_arg()),*],
+                &mut [$( $($arg.to_arg()),* )?],
             ).unwrap()
         }
     };
diff --git a/printf/src/tests.rs b/printf/src/tests.rs
index fb7446651..85b966af5 100644
--- a/printf/src/tests.rs
+++ b/printf/src/tests.rs
@@ -659,6 +659,18 @@ fn test_crate_macros() {
 
     target = crate::sprintf!("%d ok %d", 3, 4);
     assert_eq!(target, "3 ok 4");
+
+    let target = crate::sprintf!("noargs1");
+    assert_eq!(target, "noargs1");
+    let target = crate::sprintf!("noargs1",);
+    assert_eq!(target, "noargs1");
+
+    let mut target = String::new();
+    crate::sprintf!(=> &mut target, "noargs2");
+    assert_eq!(target, "noargs2");
+    let mut target = String::new();
+    crate::sprintf!(=> &mut target, "noargs2", );
+    assert_eq!(target, "noargs2");
 }
 
 #[test]