From fd16a0c79e5d13e2a08a31493e4c100913c720c3 Mon Sep 17 00:00:00 2001
From: Michael Rose <michael.rose0@gmail.com>
Date: Wed, 11 Mar 2026 22:32:06 -0700
Subject: [PATCH] Allow trailing comments in lists

---
 include/flexi_cfg/config/grammar.h |  2 +-
 tests/config_grammar_test.cpp      | 18 +++++++++++-------
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/flexi_cfg/config/grammar.h b/include/flexi_cfg/config/grammar.h
index 7230462..665c54a 100644
--- a/include/flexi_cfg/config/grammar.h
+++ b/include/flexi_cfg/config/grammar.h
@@ -101,7 +101,7 @@ struct STRING : peg::seq<peg::one<'"'>, peg::plus<peg::not_one<'"'>>, peg::one<'
 struct EXPRESSION : peg::seq<Eo, math::expression, Ec> {};
 
 template <typename Element>
-struct LIST_CONTENT_ : peg::list<Element, peg::seq<COMMA, TAIL>, peg::space> { using element = Element; };
+struct LIST_CONTENT_ : peg::list_tail<Element, peg::seq<COMMA, TAIL>, peg::space> { using element = Element; };
 
 template <typename Content>
 // TODO: Figure out how to support 'peg::if_must<>' here instead of 'peg::seq<>' so that we can get
diff --git a/tests/config_grammar_test.cpp b/tests/config_grammar_test.cpp
index 4ecf79b..dc5b982 100644
--- a/tests/config_grammar_test.cpp
+++ b/tests/config_grammar_test.cpp
@@ -408,6 +408,17 @@ const std::vector<std::string> list_test_cases = {
     "[$(ref.var2), $(ref.var1), 3.456]",
     // Verify that a mix of variables, expressions and numbers is supported
     R"([$(ref.var2), {{ 2^14 - 1}}, 0.32])",
+
+    // Verify that a list with a trailing comma is supported
+    "[0x123, 0Xabc, 0xA1B2F9,]",
+    // Verify that a list of lists with a trailing comma is supported
+    "[[1, 2, 3], [4, 5, 6,], [7, 8, 9],]",
+    // Verify that a list with a trailing comma and a trailing comment is supported
+    R"([
+        0x123,         # Another comment here with a comma,
+        0Xabc, 0xA1B2F9, # a trailing comma and a trailingcomment
+        # comment
+        ])",
     };
 
 TEST(ConfigGrammar, LIST) {
@@ -437,13 +448,6 @@ TEST(ConfigGrammar, LIST) {
     EXPECT_THROW(ret.emplace(runTest<peg::must<flexi_cfg::config::LIST, peg::eolf>>(content)),
                  flexi_cfg::config::InvalidTypeException);
   }
-  {
-    // Fails due to the trailing comma
-    const std::string content = "[0x123, 0Xabc, 0xA1B2F9,]";
-    std::optional<RetType> ret;
-    EXPECT_THROW(ret.emplace(runTest<peg::must<flexi_cfg::config::LIST, peg::eolf>>(content)),
-                 tao::pegtl::parse_error);
-  }
   {
     // Fails due to containing a VAR
     const std::string content = "[0x123, $VAR, 0xA1B2F9,]";