3 files changed, 70 insertions, 0 deletions
diff --git a/json4cpp/tests/abi/inline_ns/CMakeLists.txt b/json4cpp/tests/abi/inline_ns/CMakeLists.txt
new file mode 100644
index 0000000000..c1a0817e09
--- /dev/null
+++ b/json4cpp/tests/abi/inline_ns/CMakeLists.txt
@@ -0,0 +1,12 @@
+# test linking an old library version without an inline namespace
+# with the current library using an inline namespace into the same executable
+
+# build test executable and add test
+add_executable(abi_compat_inline_ns
+    use_v3_10_5.cpp
+    use_current.cpp)
+target_link_libraries(abi_compat_inline_ns PRIVATE abi_compat_main)
+
+add_test(
+    NAME test-abi_compat_inline_ns
+    COMMAND abi_compat_inline_ns ${DOCTEST_TEST_FILTER})
diff --git a/json4cpp/tests/abi/inline_ns/use_current.cpp b/json4cpp/tests/abi/inline_ns/use_current.cpp
new file mode 100644
index 0000000000..45d09f9c89
--- /dev/null
+++ b/json4cpp/tests/abi/inline_ns/use_current.cpp
@@ -0,0 +1,36 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  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"
+
+#include <nlohmann/json.hpp>
+
+TEST_CASE("use current library with inline namespace")
+{
+    SECTION("implicitly")
+    {
+        using nlohmann::json;
+        using nlohmann::ordered_json;
+
+        json j;
+        // In v3.10.5 mixing json_pointers of different basic_json types
+        // results in implicit string conversion
+        j[ordered_json::json_pointer("/root")] = json::object();
+        CHECK(j.dump() == "{\"root\":{}}");
+    }
+
+    SECTION("explicitly")
+    {
+        using NLOHMANN_JSON_NAMESPACE::json;
+        using NLOHMANN_JSON_NAMESPACE::ordered_json;
+
+        json j;
+        j[ordered_json::json_pointer("/root")] = json::object();
+        CHECK(j.dump() == "{\"root\":{}}");
+    }
+}
diff --git a/json4cpp/tests/abi/inline_ns/use_v3_10_5.cpp b/json4cpp/tests/abi/inline_ns/use_v3_10_5.cpp
new file mode 100644
index 0000000000..a3d08985bb
--- /dev/null
+++ b/json4cpp/tests/abi/inline_ns/use_v3_10_5.cpp
@@ -0,0 +1,22 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  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"
+
+#include <nlohmann/json_v3_10_5.hpp>
+using nlohmann::json;
+using nlohmann::ordered_json;
+
+TEST_CASE("use library v3.10.5 without inline namespace")
+{
+    json j;
+    j[ordered_json::json_pointer("/root")] = json::object();
+    // In v3.10.5 mixing json_pointers of different basic_json types
+    // results in implicit string conversion
+    CHECK(j.dump() == "{\"/root\":{}}");
+}