Patching in snapshot of (already closed) PR pybind#4316

include/pybind11/detail/internals.h

@@ -209,6 +209,11 @@ struct internals {
         PYBIND11_TLS_FREE(tstate);
     }
 #endif
+
+    std::unordered_map<std::type_index, std::vector<std::string>>
+        std_type_index_registry_unnamed_namespace;
+    std::unordered_map<std::type_index, std::vector<std::string>>
+        std_type_index_registry_named_namespace;
 };
 
 /// Additional type information which does not fit into the PyTypeObject.

tests/CMakeLists.txt

@@ -133,6 +133,8 @@ set(PYBIND11_TEST_FILES
     test_eigen_tensor_avoid_stl_array.cpp
     test_enum
     test_eval
+    test_exc_named_namespace_a.py
+    test_exc_named_namespace_b.py
     test_exceptions
     test_factory_constructors
     test_gil_scoped
@@ -156,6 +158,8 @@ set(PYBIND11_TEST_FILES
     test_tagbased_polymorphic
     test_thread
     test_union
+    test_unnamed_namespace_a
+    test_unnamed_namespace_b
     test_virtual_functions)
 
 # Invoking cmake with something like:
@@ -219,6 +223,8 @@ tests_extra_targets("test_exceptions.py;test_local_bindings.py;test_stl.py;test_
 # And add additional targets for other tests.
 tests_extra_targets("test_exceptions.py" "cross_module_interleaved_error_already_set")
 tests_extra_targets("test_gil_scoped.py" "cross_module_gil_utils")
+tests_extra_targets("test_exc_named_namespace_a.py" "named_namespace_a")
+tests_extra_targets("test_exc_named_namespace_b.py" "named_namespace_b")
 
 set(PYBIND11_EIGEN_REPO
     "https://gitlab.com/libeigen/eigen.git"

tests/named_namespace_a.cpp

@@ -0,0 +1,25 @@
+#include <pybind11/stl.h>
+
+#include "pybind11_tests.h"
+
+namespace test_named_namespace {
+struct any_struct {};
+} // namespace test_named_namespace
+
+PYBIND11_MODULE(named_namespace_a, m) {
+    m.attr("name") = "NA";
+
+    py::detail::get_internals()
+        .std_type_index_registry_named_namespace[std::type_index(
+            typeid(test_named_namespace::any_struct))]
+        .push_back("NA");
+
+    m.def("std_type_index_registry_dump", []() {
+        py::list items;
+        for (const auto &it :
+             py::detail::get_internals().std_type_index_registry_named_namespace) {
+            items.append(py::make_tuple(it.first.name(), it.second));
+        }
+        return items;
+    });
+}

tests/named_namespace_b.cpp

@@ -0,0 +1,14 @@
+#include "pybind11_tests.h"
+
+namespace test_named_namespace {
+struct any_struct {};
+} // namespace test_named_namespace
+
+PYBIND11_MODULE(named_namespace_b, m) {
+    m.attr("name") = "NB";
+
+    py::detail::get_internals()
+        .std_type_index_registry_named_namespace[std::type_index(
+            typeid(test_named_namespace::any_struct))]
+        .push_back("NB");
+}

tests/test_exc_named_namespace_a.py

@@ -0,0 +1,15 @@
+import named_namespace_a as m
+import pytest
+
+
+def test_inspect():
+    assert m.name == "NA"
+    reg = m.std_type_index_registry_dump()
+    if len(reg) == 1:
+        assert tuple(sorted(reg[0][1])) == ("NA", "NB")
+        pytest.skip("std::type_index-EQ-GOOD")
+    if len(reg) == 2:
+        assert reg[0][0] == reg[1][0]
+        assert tuple(sorted(reg[0][1] + reg[1][1])) == ("NA", "NB")
+        pytest.skip("std::type_index-NE-BAD")
+    assert reg is None  # Sure to fail.

tests/test_exc_named_namespace_b.py

@@ -0,0 +1,5 @@
+import named_namespace_b as m
+
+
+def test_inspect():
+    assert m.name == "NB"

tests/test_unnamed_namespace_a.cpp

@@ -0,0 +1,24 @@
+#include <pybind11/stl.h>
+
+#include "pybind11_tests.h"
+
+namespace {
+struct any_struct {};
+} // namespace
+
+TEST_SUBMODULE(unnamed_namespace_a, m) {
+    m.attr("name") = "UA";
+
+    py::detail::get_internals()
+        .std_type_index_registry_unnamed_namespace[std::type_index(typeid(any_struct))]
+        .push_back("UA");
+
+    m.def("std_type_index_registry_dump", []() {
+        py::list items;
+        for (const auto &it :
+             py::detail::get_internals().std_type_index_registry_unnamed_namespace) {
+            items.append(py::make_tuple(it.first.name(), it.second));
+        }
+        return items;
+    });
+}

tests/test_unnamed_namespace_a.py

@@ -0,0 +1,15 @@
+import pytest
+
+from pybind11_tests import unnamed_namespace_a as m
+
+
+def test_inspect():
+    assert m.name == "UA"
+    reg = m.std_type_index_registry_dump()
+    if len(reg) == 1:
+        assert tuple(sorted(reg[0][1])) == ("UA", "UB")
+        pytest.skip("std::type_index-EQ-BAD")
+    if len(reg) == 2:
+        assert tuple(sorted([reg[0][1][0], reg[1][1][0]])) == ("UA", "UB")
+        pytest.skip("std::type_index-NE-GOOD")
+    assert reg is None  # Sure to fail.

tests/test_unnamed_namespace_b.cpp

@@ -0,0 +1,13 @@
+#include "pybind11_tests.h"
+
+namespace {
+struct any_struct {};
+} // namespace
+
+TEST_SUBMODULE(unnamed_namespace_b, m) {
+    m.attr("name") = "UB";
+
+    py::detail::get_internals()
+        .std_type_index_registry_unnamed_namespace[std::type_index(typeid(any_struct))]
+        .push_back("UB");
+}

tests/test_unnamed_namespace_b.py

@@ -0,0 +1,5 @@
+from pybind11_tests import unnamed_namespace_b as m
+
+
+def test_inspect():
+    assert m.name == "UB"