API: Allow to use uploaded files in settings fields

src/pretix/api/serializers/settings.py

@@ -0,0 +1,77 @@
+import logging
+
+from django.core.files import File
+from django.core.files.storage import default_storage
+from django.db.models.fields.files import FieldFile
+from hierarkey.proxy import HierarkeyProxy
+from rest_framework import serializers
+from rest_framework.exceptions import ValidationError
+
+from pretix.api.serializers.fields import UploadedFileField
+from pretix.base.settings import DEFAULTS
+
+logger = logging.getLogger(__name__)
+
+
+class SettingsSerializer(serializers.Serializer):
+    default_fields = []
+
+    def __init__(self, *args, **kwargs):
+        self.changed_data = []
+        super().__init__(*args, **kwargs)
+        for fname in self.default_fields:
+            kwargs = DEFAULTS[fname].get('serializer_kwargs', {})
+            if callable(kwargs):
+                kwargs = kwargs()
+            kwargs.setdefault('required', False)
+            kwargs.setdefault('allow_null', True)
+            form_kwargs = DEFAULTS[fname].get('form_kwargs', {})
+            if callable(form_kwargs):
+                form_kwargs = form_kwargs()
+            if 'serializer_class' not in DEFAULTS[fname]:
+                raise ValidationError('{} has no serializer class'.format(fname))
+            f = DEFAULTS[fname]['serializer_class'](
+                **kwargs
+            )
+            f._label = form_kwargs.get('label', fname)
+            f._help_text = form_kwargs.get('help_text')
+            f.parent = self
+            self.fields[fname] = f
+
+    def update(self, instance: HierarkeyProxy, validated_data):
+        for attr, value in validated_data.items():
+            if isinstance(value, FieldFile):
+                # Delete old file
+                fname = instance.get(attr, as_type=File)
+                if fname:
+                    try:
+                        default_storage.delete(fname.name)
+                    except OSError:  # pragma: no cover
+                        logger.error('Deleting file %s failed.' % fname.name)
+
+                # Create new file
+                newname = default_storage.save(self.get_new_filename(value.name), value)
+                instance.set(attr, File(file=value, name=newname))
+                self.changed_data.append(attr)
+            elif isinstance(self.fields[attr], UploadedFileField):
+                if value is None:
+                    fname = instance.get(attr, as_type=File)
+                    if fname:
+                        try:
+                            default_storage.delete(fname.name)
+                        except OSError:  # pragma: no cover
+                            logger.error('Deleting file %s failed.' % fname.name)
+                    instance.delete(attr)
+                else:
+                    # file is unchanged
+                    continue
+            elif value is None:
+                instance.delete(attr)
+                self.changed_data.append(attr)
+            elif instance.get(attr, as_type=type(value)) != value:
+                instance.set(attr, value)
+                self.changed_data.append(attr)
+        return instance
+
+    def get_new_filename(self, name: str) -> str:
+        raise NotImplementedError()