python: expose essentials of utility.ConfigurationGroup.

Need that for configuring plugins -- originally thought I'd wait until
the class is reworked, but that isn't coming anytime soon given there's
insane pressure on other things, so I have to figure out a plan B.

The interface is the most barebones possible, exposing nothing that I'd
later plan to rename or remove. Just the least possible amount of APIs
to make it possible to configure plugins, and no custom type support yet
either -- if you need to write a vector, write it as a formatted string
instead, sorry.

To make it possible to test the APIs in isolation instead of through
the plugin interface, I added also a Configuration class. Also just the
least amount possible to cover the code with tests.

doc/python/conf.py

@@ -7,6 +7,7 @@ sys.path = [os.path.join(os.path.dirname(__file__), '../../build/src/python/')]
 import corrade
 import corrade.containers
 import corrade.pluginmanager
+import corrade.utility
 
 import magnum
 import magnum.gl
@@ -24,7 +25,7 @@ import magnum.trade
 
 # So the doc see everything
 # TODO: use just +=, m.css should reorder this on its own
-corrade.__all__ = ['containers', 'pluginmanager', 'BUILD_DEPRECATED', 'BUILD_STATIC', 'BUILD_MULTITHREADED', 'TARGET_UNIX', 'TARGET_APPLE', 'TARGET_IOS', 'TARGET_IOS_SIMULATOR', 'TARGET_WINDOWS', 'TARGET_WINDOWS_RT', 'TARGET_EMSCRIPTEN', 'TARGET_ANDROID']
+corrade.__all__ = ['containers', 'pluginmanager', 'utility', 'BUILD_DEPRECATED', 'BUILD_STATIC', 'BUILD_MULTITHREADED', 'TARGET_UNIX', 'TARGET_APPLE', 'TARGET_IOS', 'TARGET_IOS_SIMULATOR', 'TARGET_WINDOWS', 'TARGET_WINDOWS_RT', 'TARGET_EMSCRIPTEN', 'TARGET_ANDROID']
 magnum.__all__ = ['math', 'gl', 'meshtools', 'platform', 'primitives', 'shaders', 'scenegraph', 'text', 'trade', 'BUILD_DEPRECATED', 'BUILD_STATIC', 'TARGET_GL', 'TARGET_GLES', 'TARGET_GLES2', 'TARGET_WEBGL', 'TARGET_EGL', 'TARGET_VK'] + magnum.__all__
 
 # hide values of the preprocessor defines to avoid confusion by assigning a
@@ -176,6 +177,7 @@ INPUT_DOCS = [
     'corrade.rst',
     'corrade.containers.rst',
     'corrade.pluginmanager.rst',
+    'corrade.utility.rst',
 
     'magnum.rst',
     'magnum.gl.rst',

doc/python/corrade.utility.rst

@@ -0,0 +1,33 @@
+..
+    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.
+..
+
+.. py:function:: corrade.utility.ConfigurationGroup.group
+    :raise KeyError: If group :p:`name` doesn't exist
+
+.. py:function:: corrade.utility.Configuration.__init__
+    :raise IOError: If :p:`filename` contains a parse error
+
+.. py:function:: corrade.utility.Configuration.save
+    :raise IOError: If the file can't be saved

doc/python/pages/changelog.rst

@@ -123,6 +123,8 @@ Changelog
 -   Exposed :ref:`Color3.red()` and other convenience constructors (see
     :gh:`mosra/magnum-bindings#12`)
 -   Exposed the :ref:`text` library
+-   Exposed the minimal interface of :ref:`utility.ConfigurationGroup` and
+    :ref:`utility.Configuration`
 -   Fixed issues with an in-source build (see :gh:`mosra/magnum-bindings#13`)
 -   All CMake build options are now prefixed with ``MAGNUM_``. For backwards
     compatibility, unless ``MAGNUM_BUILD_DEPRECATED`` is disabled and unless a

src/python/CMakeLists.txt

@@ -62,6 +62,7 @@ add_subdirectory(magnum)
 foreach(target
     corrade_containers
     corrade_pluginmanager
+    corrade_utility
     magnum_gl
     magnum_meshtools
     magnum_primitives

src/python/corrade/CMakeLists.txt

@@ -43,6 +43,9 @@ set(corrade_containers_SRCS
 set(corrade_pluginmanager_SRCS
     pluginmanager.cpp)
 
+set(corrade_utility_SRCS
+    utility.cpp)
+
 # If Corrade is not built as static, compile the sub-libraries as separate
 # modules
 if(NOT CORRADE_BUILD_STATIC)
@@ -57,6 +60,16 @@ if(NOT CORRADE_BUILD_STATIC)
         OUTPUT_NAME "containers"
         LIBRARY_OUTPUT_DIRECTORY ${output_dir}/corrade)
 
+    pybind11_add_module(corrade_utility ${pybind11_add_module_SYSTEM} ${corrade_utility_SRCS})
+    target_include_directories(corrade_utility PRIVATE
+        ${PROJECT_SOURCE_DIR}/src
+        ${PROJECT_SOURCE_DIR}/src/python)
+    target_link_libraries(corrade_utility PRIVATE
+        Corrade::Utility)
+    set_target_properties(corrade_utility PROPERTIES
+        OUTPUT_NAME "utility"
+        LIBRARY_OUTPUT_DIRECTORY ${output_dir}/corrade)
+
     if(Corrade_PluginManager_FOUND)
         pybind11_add_module(corrade_pluginmanager ${pybind11_add_module_SYSTEM} ${corrade_pluginmanager_SRCS})
         target_include_directories(corrade_pluginmanager PRIVATE
@@ -76,8 +89,12 @@ else()
     configure_file(${CMAKE_CURRENT_SOURCE_DIR}/staticconfigure.h.cmake
                    ${CMAKE_CURRENT_BINARY_DIR}/staticconfigure.h)
 
-    list(APPEND corrade_SRCS ${corrade_containers_SRCS})
+    list(APPEND corrade_SRCS
-    list(APPEND corrade_LIBS Corrade::Containers)
+        ${corrade_containers_SRCS}
+        ${corrade_utility_SRCS})
+    list(APPEND corrade_LIBS
+        Corrade::Containers
+        Corrade::Utility)
 
     if(Corrade_PluginManager_FOUND)
         list(APPEND corrade_SRCS ${corrade_pluginmanager_SRCS})

src/python/corrade/__init__.py

@@ -33,7 +33,7 @@ import sys
 # _corrade. The following feels extremely hackish, but without that it wouldn't
 # be possible to do `import corrade.containers`, which is weird
 # (`from corrade import containers` works, tho, for whatever reason)
-for i in ['containers', 'pluginmanager']:
+for i in ['containers', 'pluginmanager', 'utility']:
     if i in globals(): sys.modules['corrade.' + i] = globals()[i]
 
 # Prevent all submodules being pulled in when saying `from corrade import *` --

src/python/corrade/bootstrap.h

@@ -48,6 +48,7 @@ namespace py = pybind11;
 
 void containers(py::module_& m);
 void pluginmanager(py::module_& m);
+void utility(py::module_& m);
 
 }
 

src/python/corrade/corrade.cpp

@@ -132,5 +132,8 @@ PYBIND11_MODULE(_corrade, m) {
     py::module_ pluginmanager = m.def_submodule("pluginmanager");
     corrade::pluginmanager(pluginmanager);
     #endif
+
+    py::module_ utility = m.def_submodule("utility");
+    corrade::utility(utility);
     #endif
 }

src/python/corrade/test/broken.conf

@@ -0,0 +1 @@
+]]] yes this is invalid!!!

src/python/corrade/test/file.conf

@@ -0,0 +1,6 @@
+someKey=42
+[someGroup]
+value=hello
+[someGroup/subgroup]
+anotherValue=another
+[emptyGroup]

src/python/corrade/test/test_utility.py

@@ -0,0 +1,141 @@
+#
+#   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.
+#
+
+import os
+import sys
+import tempfile
+import unittest
+
+from corrade import utility
+
+# Tests also the ConfigurationGroup bindings, as a ConfigurationGroup cannot be
+# constructed as a standalone type
+class Configuration(unittest.TestCase):
+    def test_open(self):
+        a = utility.Configuration(os.path.join(os.path.dirname(__file__), "file.conf"))
+        a_refcount = sys.getrefcount(a)
+        self.assertEqual(a['someKey'], '42')
+        self.assertEqual(a['nonexistent'], '')
+
+        b = a.group('someGroup')
+        b_refcount = sys.getrefcount(b)
+        self.assertEqual(sys.getrefcount(a), a_refcount + 1)
+        self.assertEqual(b['value'], 'hello')
+
+        c = b.group('subgroup')
+        self.assertEqual(sys.getrefcount(a), a_refcount + 1)
+        self.assertEqual(sys.getrefcount(b), b_refcount + 1)
+        self.assertEqual(c['anotherValue'], 'another')
+
+        del c
+        self.assertEqual(sys.getrefcount(b), b_refcount)
+
+        del b
+        self.assertEqual(sys.getrefcount(a), a_refcount)
+
+    def test_nonexistent_group(self):
+        a = utility.Configuration(os.path.join(os.path.dirname(__file__), "file.conf"))
+        a_refcount = sys.getrefcount(a)
+
+        with self.assertRaises(KeyError):
+            a.group('nonexistent')
+
+        self.assertEqual(sys.getrefcount(a), a_refcount)
+
+    def test_save(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            filename = os.path.join(tmp, "file.conf")
+
+            a = utility.Configuration(filename)
+            a['value'] = 'hello'
+
+            a_refcount = sys.getrefcount(a)
+            b = a.add_group('someGroup')
+            self.assertEqual(sys.getrefcount(a), a_refcount + 1)
+
+            b['someKey'] = '42'
+
+            # This should not delete the group from the configuration
+            del b
+            self.assertEqual(sys.getrefcount(a), a_refcount)
+
+            a.save()
+
+            with open(filename, 'r') as f:
+                self.assertEqual(f.read(), "value=hello\n[someGroup]\nsomeKey=42\n")
+
+    def test_save_different_filename(self):
+        a = utility.Configuration()
+        a['value'] = 'hello'
+
+        with tempfile.TemporaryDirectory() as tmp:
+            filename = os.path.join(tmp, "file.conf")
+            a.save(filename)
+
+            with open(filename, 'r') as f:
+                self.assertEqual(f.read(), "value=hello\n")
+
+    def test_save_implicit(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            filename = os.path.join(tmp, "file.conf")
+
+            a = utility.Configuration(filename)
+            a['value'] = 'hello'
+            self.assertFalse(os.path.exists(filename))
+
+            del a
+            self.assertTrue(os.path.exists(filename))
+
+            with open(filename, 'r') as f:
+                self.assertEqual(f.read(), "value=hello\n")
+
+    def test_open_nonexistent(self):
+        # This should not raise any exception as it's a valid use case (i.e,
+        # opening an app for the first time)
+        a = utility.Configuration("nonexistent.conf")
+        self.assertFalse(a.has_groups)
+        self.assertFalse(a.has_values)
+
+    def test_open_failed(self):
+        with self.assertRaises(IOError):
+            utility.Configuration(os.path.join(os.path.dirname(__file__), "broken.conf"))
+
+    @unittest.skipIf(os.access("/", os.W_OK), "root dir is writable")
+    def test_save_failed(self):
+        # The file doesn't exist, which means nothing is parsed during
+        # construction. But saving will fail as the directory is not writable.
+        a = utility.Configuration("/nonexistent.conf")
+        self.assertFalse(a.has_groups)
+        self.assertFalse(a.has_values)
+
+        with self.assertRaises(IOError):
+            a.save()
+
+    def test_save_different_filename_failed(self):
+        a = utility.Configuration()
+
+        with self.assertRaises(IOError):
+            a.save("/some/path/that/does/not/exist.conf")
+

src/python/corrade/utility.cpp

@@ -0,0 +1,95 @@
+/*
+    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 <pybind11/pybind11.h>
+#include <Corrade/Utility/Assert.h>
+#include <Corrade/Utility/Configuration.h>
+
+#include "corrade/bootstrap.h"
+
+namespace corrade {
+
+void utility(py::module_& m) {
+    m.doc() = "Utilities";
+
+    py::class_<Utility::ConfigurationGroup>{m, "ConfigurationGroup", "Group of values in a configuration file"}
+        .def_property_readonly("has_groups", &Utility::ConfigurationGroup::hasGroups, "Whether this group has any subgroups")
+        .def("group", [](Utility::ConfigurationGroup& self, const std::string& name) {
+            Utility::ConfigurationGroup* group = self.group(name);
+            if(!group) {
+                PyErr_SetNone(PyExc_KeyError);
+                throw py::error_already_set{};
+            }
+            return group;
+        }, "Group", py::arg("name"), py::return_value_policy::reference_internal)
+        .def("add_group", [](Utility::ConfigurationGroup& self, const std::string& name) {
+            Utility::ConfigurationGroup* group = self.addGroup(name);
+            CORRADE_INTERNAL_ASSERT(group);
+            return group;
+        }, "Add a group", py::arg("name"), py::return_value_policy::reference_internal)
+        .def_property_readonly("has_values", &Utility::ConfigurationGroup::hasValues, "Whether this group has any values")
+        .def("__getitem__", [](Utility::ConfigurationGroup& self, const std::string& key) {
+            /** @todo should return an Optional once ConfigurationGroup is
+                reworked */
+            return self.value(key);
+        }, "Value", py::arg("key"))
+        .def("__setitem__", [](Utility::ConfigurationGroup& self, const std::string& key, const std::string& value) {
+            self.setValue(key, value);
+        }, "Set a value", py::arg("key"), py::arg("value"));
+
+    py::class_<Utility::Configuration, Utility::ConfigurationGroup>{m, "Configuration", "Parser and writer for configuration files"}
+        .def(py::init(), "Construct an empty configuration")
+        .def(py::init([](const std::string& filename) {
+            std::unique_ptr<Utility::Configuration> self{new Utility::Configuration{filename}};
+            if(!self->isValid()) {
+                PyErr_SetNone(PyExc_IOError);
+                throw py::error_already_set{};
+            }
+            return self;
+        }), "Parse a configuration file", py::arg("filename"))
+        .def("save", [](Utility::Configuration& self) {
+            if(!self.save()) {
+                PyErr_SetNone(PyExc_IOError);
+                throw py::error_already_set{};
+            }
+        }, "Save the configuration")
+        .def("save", [](Utility::Configuration& self, const std::string& filename) {
+            if(!self.save(filename)) {
+                PyErr_SetNone(PyExc_IOError);
+                throw py::error_already_set{};
+            }
+        }, "Save the configuration to another file", py::arg("filename"));
+}
+
+}
+
+#ifndef CORRADE_BUILD_STATIC
+/* TODO: remove declaration when https://github.com/pybind/pybind11/pull/1863
+   is released */
+extern "C" PYBIND11_EXPORT PyObject* PyInit_utility();
+PYBIND11_MODULE(utility, m) {
+    corrade::utility(m);
+}
+#endif

src/python/setup.py.cmake

@@ -36,6 +36,7 @@ extension_paths = {
     '_corrade': '$<TARGET_FILE:corrade>',
     'corrade.containers': '${corrade_containers_file}',
     'corrade.pluginmanager': '${corrade_pluginmanager_file}',
+    'corrade.utility': '${corrade_utility_file}',
     '_magnum': '$<TARGET_FILE:magnum>',
     'magnum.gl': '${magnum_gl_file}',
     'magnum.meshtools': '${magnum_meshtools_file}',