From 4c5b4af04d779394fff544d91ca37d4ed8aa36e9 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@meta.com>
Date: Fri, 19 Jan 2024 16:06:06 -0800
Subject: [PATCH] Improve name argument validation

---
 include/fmt/base.h   | 4 +++-
 include/fmt/format.h | 4 +++-
 test/args-test.cc    | 6 +++---
 test/format-test.cc  | 5 ++++-
 4 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/fmt/base.h b/include/fmt/base.h
index 7d75a1bc..3850871b 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -772,7 +772,9 @@ template <typename Char> class basic_format_parse_context {
     next_arg_id_ = -1;
     do_check_arg_id(id);
   }
-  FMT_CONSTEXPR void check_arg_id(basic_string_view<Char>) {}
+  FMT_CONSTEXPR void check_arg_id(basic_string_view<Char>) {
+    next_arg_id_ = -1;
+  }
   FMT_CONSTEXPR void check_dynamic_spec(int arg_id);
 };
 
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 8df6c965..f118057e 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -4264,9 +4264,11 @@ void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
       return parse_context.next_arg_id();
     }
     FMT_CONSTEXPR auto on_arg_id(int id) -> int {
-      return parse_context.check_arg_id(id), id;
+      parse_context.check_arg_id(id);
+      return id;
     }
     FMT_CONSTEXPR auto on_arg_id(basic_string_view<Char> id) -> int {
+      parse_context.check_arg_id(id);
       int arg_id = context.arg_id(id);
       if (arg_id < 0) report_error("argument not found");
       return arg_id;
diff --git a/test/args-test.cc b/test/args-test.cc
index 9c72cb95..f99ff74e 100644
--- a/test/args-test.cc
+++ b/test/args-test.cc
@@ -144,9 +144,9 @@ TEST(args_test, reserve) {
   fmt::dynamic_format_arg_store<fmt::format_context> store;
   store.reserve(2, 1);
   store.push_back(1.5f);
-  store.push_back(fmt::arg("a1", 42));
-  auto result = fmt::vformat("{a1} and {}", store);
-  EXPECT_EQ("42 and 1.5", result);
+  store.push_back(fmt::arg("a", 42));
+  auto result = fmt::vformat("{} and {a}", store);
+  EXPECT_EQ("1.5 and 42", result);
 }
 
 struct copy_throwable {
diff --git a/test/format-test.cc b/test/format-test.cc
index db68ca08..2b8255a5 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -555,6 +555,9 @@ TEST(format_test, named_arg) {
                    "argument not found");
   EXPECT_THROW_MSG((void)fmt::format(runtime("{a}"), 42), format_error,
                    "argument not found");
+  EXPECT_THROW_MSG((void)fmt::format(runtime("{a} {}"), fmt::arg("a", 2), 42),
+                   format_error,
+                   "cannot switch from manual to automatic argument indexing");
 }
 
 TEST(format_test, auto_arg_index) {
@@ -1742,7 +1745,7 @@ TEST(format_test, print) {
 }
 
 TEST(format_test, big_print) {
-  enum {count = 5000};
+  enum { count = 5000 };
   auto big_print = []() {
     for (int i = 0; i < count / 5; ++i) fmt::print("xxxxx");
   };