python: put PyPluginHolder into a public header as well.

Will need it for exposing Trade::AbstractImporter instances returned
from SceneTools.

src/Corrade/CMakeLists.txt

@@ -33,3 +33,7 @@ if(MAGNUM_WITH_PYTHON)
 endif()
 
 add_subdirectory(Containers)
+
+if(Corrade_PluginManager_FOUND)
+    add_subdirectory(PluginManager)
+endif()

src/Corrade/PluginManager/CMakeLists.txt

@@ -0,0 +1,32 @@
+#
+#   This file is part of Magnum.
+#
+#   Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,
+#               2020, 2021, 2022 Vladimír Vondruš <mosra@centrum.cz>
+#
+#   Permission is hereby granted, free of charge, to any person obtaining a
+#   copy of this software and associated documentation files (the "Software"),
+#   to deal in the Software without restriction, including without limitation
+#   the rights to use, copy, modify, merge, publish, distribute, sublicense,
+#   and/or sell copies of the Software, and to permit persons to whom the
+#   Software is furnished to do so, subject to the following conditions:
+#
+#   The above copyright notice and this permission notice shall be included
+#   in all copies or substantial portions of the Software.
+#
+#   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+#   THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+#   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+#   DEALINGS IN THE SOFTWARE.
+#
+
+if(MAGNUM_WITH_PYTHON)
+    set(CorradePluginManagerPython_HEADERS
+        PythonBindings.h)
+
+    add_custom_target(CorradePluginManagerPython SOURCES ${CorradePluginManagerPython_HEADERS})
+    install(FILES ${CorradePluginManagerPython_HEADERS} DESTINATION ${CORRADE_INCLUDE_INSTALL_DIR}/PluginManager)
+endif()

src/Corrade/PluginManager/PythonBindings.h

@@ -0,0 +1,71 @@
+#ifndef Corrade_PluginManager_PythonBindings_h
+#define Corrade_PluginManager_PythonBindings_h
+/*
+    This file is part of Magnum.
+
+    Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,
+                2020, 2021, 2022 Vladimír Vondruš <mosra@centrum.cz>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included
+    in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+*/
+
+#include <memory> /* :( */
+#include <pybind11/pybind11.h>
+#include <Corrade/Containers/Pointer.h>
+#include <Corrade/Utility/Assert.h>
+
+namespace Corrade { namespace PluginManager {
+
+/* Stores additional stuff needed for proper refcounting of plugin instances.
+   Due to obvious reasons we can't subclass plugins so this is the only
+   possible way. */
+template<class T> struct PyPluginHolder: std::unique_ptr<T> {
+    explicit PyPluginHolder(T* object) noexcept: std::unique_ptr<T>{object} {
+        /* Plugin instance without an owner can only be without a manager and
+           thus without any metadata */
+        CORRADE_INTERNAL_ASSERT(!object->metadata());
+    }
+
+    explicit PyPluginHolder(T* object, pybind11::object manager) noexcept: std::unique_ptr<T>{object}, manager{std::move(manager)} {}
+
+    PyPluginHolder(PyPluginHolder<T>&&) noexcept = default;
+    PyPluginHolder(const PyPluginHolder<T>&) = delete;
+    PyPluginHolder<T>& operator=(PyPluginHolder<T>&&) noexcept = default;
+    PyPluginHolder<T>& operator=(const PyPluginHolder<T>&) = default;
+
+    ~PyPluginHolder() {
+        /* On destruction, first `manager` and then the plugin would be
+           destroyed, which would mean it asserts due to the manager being
+           destructed while plugins are still around. To flip the order, we
+           need to reset the pointer first */
+        std::unique_ptr<T>::reset();
+    }
+
+    pybind11::object manager;
+};
+
+template<class T> PyPluginHolder<T> pyPluginHolder(Containers::Pointer<T>&& plugin, pybind11::object owner) {
+    return PyPluginHolder<T>{plugin.release(), std::move(owner)};
+}
+
+}}
+
+PYBIND11_DECLARE_HOLDER_TYPE(T, Corrade::PluginManager::PyPluginHolder<T>)
+
+#endif

src/python/corrade/pluginmanager.h

@@ -33,42 +33,10 @@
 #include <Corrade/PluginManager/Manager.h>
 
 #include "Corrade/PythonBindings.h"
+#include "Corrade/PluginManager/PythonBindings.h"
 
 #include "corrade/bootstrap.h"
 
-namespace Corrade { namespace PluginManager {
-
-/* Stores additional stuff needed for proper refcounting of plugin instances.
-   Due to obvious reasons we can't subclass plugins so this is the only
-   possible way. */
-template<class T> struct PyPluginHolder: std::unique_ptr<T> {
-    explicit PyPluginHolder(T*) {
-        /* Pybind needs this signature, but it should never be called */
-        CORRADE_INTERNAL_ASSERT_UNREACHABLE();
-    }
-
-    explicit PyPluginHolder(T* object, pybind11::object manager) noexcept: std::unique_ptr<T>{object}, manager{std::move(manager)} {}
-
-    PyPluginHolder(PyPluginHolder<T>&&) noexcept = default;
-    PyPluginHolder(const PyPluginHolder<T>&) = delete;
-    PyPluginHolder<T>& operator=(PyPluginHolder<T>&&) noexcept = default;
-    PyPluginHolder<T>& operator=(const PyPluginHolder<T>&) = default;
-
-    ~PyPluginHolder() {
-        /* On destruction, first `manager` and then the plugin would be
-           destroyed, which would mean it asserts due to the manager being
-           destructed while plugins are still around. To flip the order, we
-           need to reset the pointer first */
-        std::unique_ptr<T>::reset();
-    }
-
-    pybind11::object manager;
-};
-
-}}
-
-PYBIND11_DECLARE_HOLDER_TYPE(T, Corrade::PluginManager::PyPluginHolder<T>)
-
 namespace corrade {
 
 template<class T> void plugin(py::class_<T, PluginManager::PyPluginHolder<T>, PluginManager::AbstractPlugin>& c) {
@@ -115,7 +83,7 @@ template<class T> void manager(py::class_<PluginManager::Manager<T>, PluginManag
                 throw py::error_already_set{};
             }
 
-            return PluginManager::PyPluginHolder<T>{loaded.release(), py::cast(self)};
+            return PluginManager::pyPluginHolder(std::move(loaded), py::cast(self));
         })
         .def("load_and_instantiate", [](PluginManager::Manager<T>& self, const std::string& plugin) {
             auto loaded = self.loadAndInstantiate(plugin);
@@ -124,7 +92,7 @@ template<class T> void manager(py::class_<PluginManager::Manager<T>, PluginManag
                 throw py::error_already_set{};
             }
 
-            return PluginManager::PyPluginHolder<T>{loaded.release(), py::cast(self)};
+            return PluginManager::pyPluginHolder(std::move(loaded), py::cast(self));
         });
 }