From c4f66027b6cff06c6fc2bd98caf61926d5e5edfd Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 2 Feb 2022 07:07:04 -0800
Subject: [PATCH] [Experiment] `boost::typeindex::type_index` & unnamed
 namespace

Related to PR #4313
---
 include/pybind11/detail/internals.h | 10 ++++++++++
 tests/CMakeLists.txt                |  2 ++
 tests/test_unnamed_namespace_a.cpp  | 30 +++++++++++++++++++++++++++++
 tests/test_unnamed_namespace_a.py   | 17 ++++++++++++++++
 tests/test_unnamed_namespace_b.cpp  | 16 +++++++++++++++
 tests/test_unnamed_namespace_b.py   |  5 +++++
 6 files changed, 80 insertions(+)
 create mode 100644 tests/test_unnamed_namespace_a.cpp
 create mode 100644 tests/test_unnamed_namespace_a.py
 create mode 100644 tests/test_unnamed_namespace_b.cpp
 create mode 100644 tests/test_unnamed_namespace_b.py

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 6fd61098c4..2c110c85b7 100644
--- a/include/pybind11/detail/internals.h
+++ b/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.
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 491f215cef..285f43b5b9 100644
--- a/tests/CMakeLists.txt
+++ b/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:
diff --git a/tests/test_unnamed_namespace_a.cpp b/tests/test_unnamed_namespace_a.cpp
new file mode 100644
index 0000000000..8df9ffd24d
--- /dev/null
+++ b/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
+    });
+}
diff --git a/tests/test_unnamed_namespace_a.py b/tests/test_unnamed_namespace_a.py
new file mode 100644
index 0000000000..59eb3ca56d
--- /dev/null
+++ b/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.
diff --git a/tests/test_unnamed_namespace_b.cpp b/tests/test_unnamed_namespace_b.cpp
new file mode 100644
index 0000000000..c137fbce3d
--- /dev/null
+++ b/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
+}
diff --git a/tests/test_unnamed_namespace_b.py b/tests/test_unnamed_namespace_b.py
new file mode 100644
index 0000000000..4409bb45aa
--- /dev/null
+++ b/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"