From 5e6d1e29f7546d9d94fe3d193b788b280bf1f37d Mon Sep 17 00:00:00 2001
From: Victor Proon <vicproon@gmail.com>
Date: Fri, 18 Jul 2025 00:09:03 +0300
Subject: [PATCH] fix the issue with default empty vectors behaviour. update
 unit test (#460)

---
 include/cxxopts.hpp |  9 +++------
 test/options.cpp    | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/include/cxxopts.hpp b/include/cxxopts.hpp
index 32c8f2c..b9c7407 100644
--- a/include/cxxopts.hpp
+++ b/include/cxxopts.hpp
@@ -1100,22 +1100,19 @@ void parse_value(const std::string& text, char& c)
   c = text[0];
 }
 
+template<typename T> void add_value(const std::string& text, std::vector<T>& value);
+
 template <typename T>
 void
 parse_value(const std::string& text, std::vector<T>& value)
 {
   if (text.empty()) {
-    T v;
-    parse_value(text, v);
-    value.emplace_back(std::move(v));
     return;
   }
   std::stringstream in(text);
   std::string token;
   while(!in.eof() && std::getline(in, token, CXXOPTS_VECTOR_DELIMITER)) {
-    T v;
-    parse_value(token, v);
-    value.emplace_back(std::move(v));
+    add_value(token, value);
   }
 }
 
diff --git a/test/options.cpp b/test/options.cpp
index 843f4ae..6df4972 100644
--- a/test/options.cpp
+++ b/test/options.cpp
@@ -709,6 +709,40 @@ TEST_CASE("std::vector", "[vector]") {
   CHECK(vector[3] == 4.5);
 }
 
+TEST_CASE("empty std::vector", "[vector]") {
+  std::vector<double> double_vector;
+  std::vector<std::string> string_vector;
+
+  cxxopts::Options options("empty vector", " - tests behaviour of empty vector options");
+
+  SECTION("string vector") {
+    options.add_options()
+        ("string_vector", "vector of strings", cxxopts::value(string_vector)->default_value(""));
+
+    Argv av({"empty vector"});
+    auto** argv = av.argv();
+    auto argc = av.argc();
+
+    options.parse(argc, argv);
+
+    CHECK(string_vector.empty());
+  }
+
+  SECTION("double vector") {
+    options.add_options()
+        ("double_vector", "vector of doubles", cxxopts::value(double_vector)->default_value(""));
+
+    Argv av({"empty vector"});
+    auto** argv = av.argv();
+    auto argc = av.argc();
+
+    options.parse(argc, argv); // throws
+
+    CHECK(double_vector.empty());
+  }
+
+}
+
 #ifdef CXXOPTS_HAS_OPTIONAL
 TEST_CASE("std::optional", "[optional]") {
   std::optional<std::string> optional;