1 files changed, 166 insertions, 0 deletions
diff --git a/json4cpp/tests/src/unit-locale-cpp.cpp b/json4cpp/tests/src/unit-locale-cpp.cpp
new file mode 100644
index 0000000000..0019d3b923
--- /dev/null
+++ b/json4cpp/tests/src/unit-locale-cpp.cpp
@@ -0,0 +1,166 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#include "doctest_compatibility.h"
+
+#define JSON_TESTS_PRIVATE
+#include <nlohmann/json.hpp>
+using nlohmann::json;
+
+#include <clocale>
+
+struct ParserImpl final: public nlohmann::json_sax<json>
+{
+    bool null() override
+    {
+        return true;
+    }
+    bool boolean(bool /*val*/) override
+    {
+        return true;
+    }
+    bool number_integer(json::number_integer_t /*val*/) override
+    {
+        return true;
+    }
+    bool number_unsigned(json::number_unsigned_t /*val*/) override
+    {
+        return true;
+    }
+    bool number_float(json::number_float_t /*val*/, const json::string_t& s) override
+    {
+        float_string_copy = s;
+        return true;
+    }
+    bool string(json::string_t& /*val*/) override
+    {
+        return true;
+    }
+    bool binary(json::binary_t& /*val*/) override
+    {
+        return true;
+    }
+    bool start_object(std::size_t /*val*/) override
+    {
+        return true;
+    }
+    bool key(json::string_t& /*val*/) override
+    {
+        return true;
+    }
+    bool end_object() override
+    {
+        return true;
+    }
+    bool start_array(std::size_t /*val*/) override
+    {
+        return true;
+    }
+    bool end_array() override
+    {
+        return true;
+    }
+    bool parse_error(std::size_t /*val*/, const std::string& /*val*/, const nlohmann::detail::exception& /*val*/) override
+    {
+        return false;
+    }
+
+    ~ParserImpl() override;
+
+    ParserImpl()
+        : float_string_copy("not set")
+    {}
+
+    ParserImpl(const ParserImpl& other)
+        : float_string_copy(other.float_string_copy)
+    {}
+
+    ParserImpl(ParserImpl&& other) noexcept
+        : float_string_copy(std::move(other.float_string_copy))
+    {}
+
+    ParserImpl& operator=(const ParserImpl& other)
+    {
+        if (this != &other)
+        {
+            float_string_copy = other.float_string_copy;
+        }
+        return *this;
+    }
+
+    ParserImpl& operator=(ParserImpl&& other) noexcept
+    {
+        if (this != &other)
+        {
+            float_string_copy = std::move(other.float_string_copy);
+        }
+        return *this;
+    }
+
+    json::string_t float_string_copy;
+};
+
+ParserImpl::~ParserImpl() = default;
+
+TEST_CASE("locale-dependent test (LC_NUMERIC=C)")
+{
+    WARN_MESSAGE(std::setlocale(LC_NUMERIC, "C") != nullptr, "could not set locale");
+
+    SECTION("check if locale is properly set")
+    {
+        std::array<char, 6> buffer = {};
+        CHECK(std::snprintf(buffer.data(), buffer.size(), "%.2f", 12.34) == 5); // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+        CHECK(std::string(buffer.data()) == "12.34");
+    }
+
+    SECTION("parsing")
+    {
+        CHECK(json::parse("12.34").dump() == "12.34");
+    }
+
+    SECTION("SAX parsing")
+    {
+        ParserImpl sax {};
+        json::sax_parse( "12.34", &sax );
+        CHECK(sax.float_string_copy == "12.34");
+    }
+}
+
+TEST_CASE("locale-dependent test (LC_NUMERIC=de_DE)")
+{
+    if (std::setlocale(LC_NUMERIC, "de_DE") != nullptr)
+    {
+        SECTION("check if locale is properly set")
+        {
+            std::array<char, 6> buffer = {};
+            CHECK(std::snprintf(buffer.data(), buffer.size(), "%.2f", 12.34) == 5); // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+            const auto snprintf_result = std::string(buffer.data());
+            if (snprintf_result != "12,34")
+            {
+                CAPTURE(snprintf_result)
+                MESSAGE("To test if number parsing is locale-independent, we set the locale to de_DE. However, on this system, the decimal separator doesn't change to `,` potentially due to a known musl issue (https://github.com/nlohmann/json/issues/4767).");
+            }
+        }
+
+        SECTION("parsing")
+        {
+            CHECK(json::parse("12.34").dump() == "12.34");
+        }
+
+        SECTION("SAX parsing")
+        {
+            ParserImpl sax{};
+            json::sax_parse("12.34", &sax);
+            CHECK(sax.float_string_copy == "12.34");
+        }
+    }
+    else
+    {
+        MESSAGE("locale de_DE is not usable");
+    }
+}