LogEntryType registry (#4235)

Move display of LogEntry details from the `logentry_display` and 
`logentry_object_link` signals to a class hierarchy based approach. 
For each action_type, an instance of a subclass of `LogEntryType` 
is registered in the `log_entry_types` registry.

Analogous to EventPluginSignal, this registry is an `EventPluginRegistry`, 
so it keeps track of the plugin the LogEntryType is defined in.

---------

Co-authored-by: Raphael Michel <michel@rami.io>
Co-authored-by: Richard Schreiber <schreiber@rami.io>

src/tests/base/test_registry.py

@@ -0,0 +1,179 @@
+#
+# This file is part of pretix (Community Edition).
+#
+# Copyright (C) 2014-2020 Raphael Michel and contributors
+# Copyright (C) 2020-2021 rami.io GmbH and contributors
+#
+# This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General
+# Public License as published by the Free Software Foundation in version 3 of the License.
+#
+# ADDITIONAL TERMS APPLY: Pursuant to Section 7 of the GNU Affero General Public License, additional terms are
+# applicable granting you additional permissions and placing additional restrictions on your usage of this software.
+# Please refer to the pretix LICENSE file to obtain the full terms applicable to this work. If you did not receive
+# this file, see <https://pretix.eu/about/en/license>.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
+# <https://www.gnu.org/licenses/>.
+#
+from unittest import mock
+
+import pytest
+
+from pretix.base.logentrytypes import (
+    ItemLogEntryType, LogEntryType, LogEntryTypeRegistry,
+)
+from pretix.base.signals import Registry
+
+
+def test_registry_classes():
+    animal_type_registry = Registry({"type": lambda s: s.__name__, "classis": lambda s: s.classis})
+
+    @animal_type_registry.register
+    class Cat:
+        classis = 'mammalia'
+
+        def make_sound(self):
+            return "meow"
+
+    @animal_type_registry.register
+    class Dog:
+        classis = 'mammalia'
+
+        def make_sound(self):
+            return "woof"
+
+    @animal_type_registry.register
+    class Cricket:
+        classis = 'insecta'
+
+        def make_sound(self):
+            return "chirp"
+
+    # test retrieving and instantiating a class based on metadata value
+    clz, meta = animal_type_registry.get(type="Cat")
+    assert clz().make_sound() == "meow"
+    assert meta.get('type') == "Cat"
+
+    clz, meta = animal_type_registry.get(type="Dog")
+    assert clz().make_sound() == "woof"
+    assert meta.get('type') == "Dog"
+
+    # check that None is returned when no class exists with the specified metadata value
+    clz, meta = animal_type_registry.get(type="Unicorn")
+    assert clz is None
+    assert meta is None
+
+    # check that an error is raised when trying to retrieve by an undefined metadata key
+    with pytest.raises(Exception):
+        _, _ = animal_type_registry.get(whatever="hello")
+
+    # test finding all entries with a given metadata value
+    mammals = animal_type_registry.filter(classis='mammalia')
+    assert set(cls for cls, meta in mammals) == {Cat, Dog}
+    assert all(meta['classis'] == 'mammalia' for cls, meta in mammals)
+
+    insects = animal_type_registry.filter(classis='insecta')
+    assert set(cls for cls, meta in insects) == {Cricket}
+
+    fantasy = animal_type_registry.filter(classis='fantasia')
+    assert set(cls for cls, meta in fantasy) == set()
+
+    # check normal object instantiation still works with our decorator
+    assert Cat().make_sound() == "meow"
+
+
+def test_registry_instances():
+    animal_sound_registry = Registry({"animal": lambda s: s.animal})
+
+    @animal_sound_registry.new("dog", "woof")
+    @animal_sound_registry.new("cricket", "chirp")
+    class AnimalSound:
+        def __init__(self, animal, sound):
+            self.animal = animal
+            self.sound = sound
+
+        def make_sound(self):
+            return self.sound
+
+    @animal_sound_registry.new()
+    class CatSound(AnimalSound):
+        def __init__(self):
+            super().__init__(animal="cat", sound=["meow", "meww", "miaou"])
+            self.i = 0
+
+        def make_sound(self):
+            self.i += 1
+            return self.sound[self.i % len(self.sound)]
+
+    # test registry
+    assert animal_sound_registry.get(animal='dog')[0].make_sound() == "woof"
+    assert animal_sound_registry.get(animal='dog')[0].make_sound() == "woof"
+    assert animal_sound_registry.get(animal='cricket')[0].make_sound() == "chirp"
+    assert animal_sound_registry.get(animal='cat')[0].make_sound() == "meww"
+    assert animal_sound_registry.get(animal='cat')[0].make_sound() == "miaou"
+    assert animal_sound_registry.get(animal='cat')[0].make_sound() == "meow"
+
+    # check normal object instantiation still works with our decorator
+    assert AnimalSound("test", "test").make_sound() == "test"
+
+
+def test_registry_prevent_duplicates():
+    my_registry = Registry({"animal": lambda s: s.animal})
+
+    class AnimalSound:
+        def __init__(self, animal, sound):
+            self.animal = animal
+            self.sound = sound
+
+    cat = AnimalSound("cat", "meow")
+    my_registry.register(cat)
+
+    with pytest.raises(RuntimeError):
+        my_registry.register(cat)
+
+
+def test_logentrytype_registry():
+    reg = LogEntryTypeRegistry()
+
+    with mock.patch('pretix.base.signals.get_defining_app') as mock_get_defining_app:
+        mock_get_defining_app.return_value = 'my_plugin'
+
+        @reg.new("foo.mytype")
+        class MyType(LogEntryType):
+            pass
+
+    @reg.new("foo.myothertype")
+    class MyOtherType(LogEntryType):
+        pass
+
+    typ, meta = reg.get(action_type="foo.mytype")
+    assert isinstance(typ, MyType)
+    assert meta['action_type'] == "foo.mytype"
+    assert meta['plugin'] == 'my_plugin'
+
+    typ, meta = reg.get(action_type="foo.myothertype")
+    assert isinstance(typ, MyOtherType)
+    assert meta['action_type'] == "foo.myothertype"
+    assert meta['plugin'] is None
+
+    by_my_plugin = reg.filter(plugin='my_plugin')
+    assert set(type(typ) for typ, meta in by_my_plugin) == {MyType}
+
+
+def test_logentrytype_registry_validation():
+    reg = LogEntryTypeRegistry()
+
+    with pytest.raises(TypeError, match='Must not register base classes, only derived ones'):
+        reg.register(LogEntryType("foo.mytype"))
+
+    with pytest.raises(TypeError, match='Must not register base classes, only derived ones'):
+        reg.new_from_dict({"foo.mytype": "My Log Entry"})(ItemLogEntryType)
+
+    with pytest.raises(TypeError, match='Entries must be derived from LogEntryType'):
+        @reg.new()
+        class MyType:
+            pass