[Experiment] boost::typeindex::type_index & unnamed namespace

Related to PR pybind#4313

include/pybind11/detail/internals.h

@@ -17,6 +17,11 @@
 
 #include "../pytypes.h"
 
+#if defined(PYBIND11_TEST_BOOST)
+#    include <boost/type_index.hpp>
+#    include <boost/unordered_map.hpp>
+#endif
+
 #include <exception>
 
 /// Tracks the `internals` and `type_info` ABI version independent of the main library version.
@@ -209,6 +214,11 @@ struct internals {
         PYBIND11_TLS_FREE(tstate);
     }
 #endif
+
+#if defined(PYBIND11_TEST_BOOST)
+    boost::unordered_map<boost::typeindex::type_index, std::vector<std::string>>
+        boost_type_index_registry;
+#endif
 };
 
 /// Additional type information which does not fit into the PyTypeObject.

tests/CMakeLists.txt

@@ -156,6 +156,8 @@ 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:

tests/test_unnamed_namespace_a.cpp

@@ -0,0 +1,30 @@
+#include <pybind11/stl.h>
+
+#include "pybind11_tests.h"
+
+namespace {
+struct any_struct {};
+} // namespace
+
+TEST_SUBMODULE(unnamed_namespace_a, m) {
+    m.attr("name") = "A";
+
+#if defined(PYBIND11_TEST_BOOST)
+    py::detail::get_internals()
+        .boost_type_index_registry[boost::typeindex::type_index(
+            boost::typeindex::type_id<any_struct>())]
+        .push_back("A");
+#endif
+
+    m.def("boost_type_index_registry_dump", []() {
+#if defined(PYBIND11_TEST_BOOST)
+        py::list items;
+        for (const auto &it : py::detail::get_internals().boost_type_index_registry) {
+            items.append(py::make_tuple(it.first.pretty_name(), it.second));
+        }
+        return items;
+#else
+        return py::none();
+#endif
+    });
+}

tests/test_unnamed_namespace_a.py

@@ -0,0 +1,17 @@
+import pytest
+
+from pybind11_tests import unnamed_namespace_a as m
+
+
+def test_inspect():
+    assert m.name == "A"
+    reg = m.boost_type_index_registry_dump()
+    if reg is None:
+        pytest.skip("boost::typeindex::type_index-NotAvailable")
+    if len(reg) == 1:
+        assert tuple(sorted(reg[0][1])) == ("A", "B")
+        pytest.skip("boost::typeindex::type_index-EQ-BAD")
+    if len(reg) == 2:
+        assert tuple(sorted([reg[0][1][0], reg[1][1][0]])) == ("A", "B")
+        pytest.skip("boost::typeindex::type_index-NE-GOOD")
+    assert reg is None  # Sure to fail.

tests/test_unnamed_namespace_b.cpp

@@ -0,0 +1,16 @@
+#include "pybind11_tests.h"
+
+namespace {
+struct any_struct {};
+} // namespace
+
+TEST_SUBMODULE(unnamed_namespace_b, m) {
+    m.attr("name") = "B";
+
+#if defined(PYBIND11_TEST_BOOST)
+    py::detail::get_internals()
+        .boost_type_index_registry[boost::typeindex::type_index(
+            boost::typeindex::type_id<any_struct>())]
+        .push_back("B");
+#endif
+}

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 == "B"