From 3f38f9511b23ca2e73ae20dff55b89b5b192e078 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 9 Dec 2025 13:25:32 -0500
Subject: [PATCH] cmArgumentParser: Add support for MaybeEmpty<std::string>

Add it for completeness, though it is the same as plain `std::string`.
Also extend the SunPro/EDG workaround to cover this type.
---
 Source/cmArgumentParser.cxx    | 10 ++++++++++
 Source/cmArgumentParser.h      |  1 +
 Source/cmArgumentParserTypes.h |  6 ++++++
 3 files changed, 17 insertions(+)

diff --git a/Source/cmArgumentParser.cxx b/Source/cmArgumentParser.cxx
index 765e9cb88c..b2d55573de 100644
--- a/Source/cmArgumentParser.cxx
+++ b/Source/cmArgumentParser.cxx
@@ -72,6 +72,16 @@ void Instance::Bind(std::string& val)
     ExpectAtLeast{ 1 });
 }
 
+void Instance::Bind(MaybeEmpty<std::string>& val)
+{
+  this->Bind(
+    [&val](cm::string_view arg) -> Continue {
+      val = std::string(arg);
+      return Continue::No;
+    },
+    ExpectAtLeast{ 1 });
+}
+
 void Instance::Bind(NonEmpty<std::string>& val)
 {
   this->Bind(
diff --git a/Source/cmArgumentParser.h b/Source/cmArgumentParser.h
index 2b37869817..0628bb441d 100644
--- a/Source/cmArgumentParser.h
+++ b/Source/cmArgumentParser.h
@@ -212,6 +212,7 @@ public:
   void Bind(std::function<Continue(cm::string_view)> f, ExpectAtLeast expect);
   void Bind(bool& val);
   void Bind(std::string& val);
+  void Bind(MaybeEmpty<std::string>& val);
   void Bind(NonEmpty<std::string>& val);
   void Bind(Maybe<std::string>& val);
   void Bind(MaybeEmpty<std::vector<std::string>>& val);
diff --git a/Source/cmArgumentParserTypes.h b/Source/cmArgumentParserTypes.h
index bd14f9bd80..6ac71ca5cb 100644
--- a/Source/cmArgumentParserTypes.h
+++ b/Source/cmArgumentParserTypes.h
@@ -36,6 +36,12 @@ struct MaybeEmpty<std::vector<T>> : public std::vector<T>
   using std::vector<T>::vector;
   using std::vector<T>::operator=;
 };
+template <>
+struct MaybeEmpty<std::string> : public std::string
+{
+  using std::string::basic_string;
+  using std::string::operator=;
+};
 
 template <typename T>
 struct NonEmpty;