python: expose pluginmanager.AbstractManager.set_preferred_plugins().

It used to take an initializer list, not anymore. Will test this better
once I have to build e.g. AssimpImporter for some other reason -- then I
can use this function to prefer it for loading glTFs and see how that
manages.

doc/python/corrade.pluginmanager.rst

@@ -34,3 +34,6 @@
 .. py:function:: corrade.pluginmanager.AbstractManager.unload
     :raise RuntimeError: When unloading fails
     :return: Either :ref:`LoadState.NOT_LOADED` or :ref:`LoadState.STATIC`
+
+.. py:function:: corrade.pluginmanager.AbstractManager.set_preferred_plugins
+    :raise KeyError: If the alias doesn't exist

doc/python/pages/changelog.rst

@@ -125,6 +125,7 @@ Changelog
 -   Exposed the :ref:`text` library
 -   Exposed the minimal interface of :ref:`utility.ConfigurationGroup` and
     :ref:`utility.Configuration`
+-   Exposed :ref:`pluginmanager.AbstractManager.set_preferred_plugins()`
 -   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/corrade/pluginmanager.cpp

@@ -27,6 +27,7 @@
 #include <pybind11/stl.h> /* for pluginList() and aliasList() */
 #include <Corrade/Containers/Array.h>
 #include <Corrade/Containers/StringStl.h> /** @todo drop once we have our string casters */
+#include <Corrade/Containers/StringIterable.h>
 #include <Corrade/PluginManager/AbstractManager.h>
 
 #include "Corrade/PythonBindings.h"
@@ -69,7 +70,19 @@ void pluginmanager(py::module_& m) {
                 self.setPluginDirectory(directory);
             }, "Plugin directory")
         .def("reload_plugin_directory", &PluginManager::AbstractManager::reloadPluginDirectory, "Reload plugin directory")
-        /** @todo setPreferredPlugins (takes an init list) */
+        .def("set_preferred_plugins", [](PluginManager::AbstractManager& self, const std::string& alias, const std::vector<std::string>& plugins) {
+            if(self.loadState(alias) == PluginManager::LoadState::NotFound) {
+                PyErr_SetNone(PyExc_KeyError);
+                throw py::error_already_set{};
+            }
+
+            /** @todo drop all this once StringIterable can be a view on
+                std::strings */
+            Containers::Array<Containers::StringView> pluginViews{NoInit, plugins.size()};
+            for(std::size_t i = 0; i != plugins.size(); ++i)
+                pluginViews[i] = plugins[i];
+            self.setPreferredPlugins(alias, pluginViews);
+        }, "Set preferred plugins for given alias", py::arg("alias"), py::arg("plugins"))
         .def_property_readonly("plugin_list", [](PluginManager::AbstractManager& self) {
             /** @todo make a generic caster for arbitrary arrays and strings */
             std::vector<std::string> out;

src/python/magnum/test/test_trade.py

@@ -1001,6 +1001,17 @@ class Importer(unittest.TestCase):
         with self.assertRaisesRegex(RuntimeError, "can't unload plugin"):
             manager.unload('NonexistentImporter')
 
+    def test_set_preferred_plugins(self):
+        manager = trade.ImporterManager()
+        # TODO test this better once we can verify it gets actually loaded
+        manager.set_preferred_plugins('TgaImporter', ['StbImageImporter', 'DevIlImageImporter'])
+        self.assertIn('StbImageImporter', manager.alias_list)
+
+    def test_set_preferred_plugins_alias_not_found(self):
+        manager = trade.ImporterManager()
+        with self.assertRaises(KeyError):
+            manager.set_preferred_plugins('ApngImporter', [])
+
     def test_no_file_opened(self):
         importer = trade.ImporterManager().load_and_instantiate('StbImageImporter')
         self.assertFalse(importer.is_opened)