API: Allow to set product pictures

doc/api/resources/items.rst

@@ -36,8 +36,8 @@ admission                             boolean                    ``true`` for it
                                                                  (such as primary tickets) and ``false`` for others
                                                                  (such as add-ons or merchandise).
 position                              integer                    An integer, used for sorting
-picture                               string                     A product picture to be displayed in the shop
+picture                               file                       A product picture to be displayed in the shop
-                                                                 (read-only, can be ``null``).
+                                                                 (can be ``null``).
 sales_channels                        list of strings            Sales channels this product is available on, such as
                                                                  ``"web"`` or ``"resellers"``. Defaults to ``["web"]``.
 available_from                        datetime                   The first date time at which this item can be bought

src/pretix/api/serializers/fields.py

@@ -27,3 +27,50 @@ class ListMultipleChoiceField(serializers.MultipleChoiceField):
         ]
 
         return remove_duplicates_from_list(representation_data)
+
+
+class UploadedFileField(serializers.Field):
+    default_error_messages = {
+        'required': 'No file was submitted.',
+        'not_found': 'The submitted file ID was not found.',
+        'invalid_type': 'The submitted file has a file type that is not allowed in this field.',
+        'size': 'The submitted file is too large to be used in this field.',
+    }
+
+    def __init__(self, *args, **kwargs):
+        self.allowed_types = kwargs.pop('allowed_types', None)
+        self.max_size = kwargs.pop('max_size', None)
+        super().__init__(*args, **kwargs)
+
+    def to_internal_value(self, data):
+        from pretix.base.models import CachedFile
+
+        request = self.context.get('request', None)
+        try:
+            cf = CachedFile.objects.get(
+                session_key=f'api-upload-{str(type(request.user or request.auth))}-{(request.user or request.auth).pk}',
+                file__isnull=False,
+                pk=data[len("file:"):],
+            )
+        except CachedFile.DoesNotExist:
+            self.fail('not_found')
+
+        if self.allowed_types and cf.type not in self.allowed_types:
+            self.fail('invalid_type')
+        if self.max_size and cf.file.size > self.max_size:
+            self.fail('size')
+
+        return cf.file
+
+    def to_representation(self, value):
+        if not value:
+            return None
+
+        try:
+            url = value.url
+        except AttributeError:
+            return None
+        request = self.context.get('request', None)
+        if request is not None:
+            return request.build_absolute_uri(url)
+        return url

src/pretix/api/serializers/item.py

@@ -7,6 +7,7 @@ from django.utils.translation import gettext_lazy as _
 from rest_framework import serializers
 
 from pretix.api.serializers.event import MetaDataField
+from pretix.api.serializers.fields import UploadedFileField
 from pretix.api.serializers.i18n import I18nAwareModelSerializer
 from pretix.base.models import (
     Item, ItemAddOn, ItemBundle, ItemCategory, ItemMetaValue, ItemVariation,
@@ -113,6 +114,9 @@ class ItemSerializer(I18nAwareModelSerializer):
     variations = InlineItemVariationSerializer(many=True, required=False)
     tax_rate = ItemTaxRateField(source='*', read_only=True)
     meta_data = MetaDataField(required=False, source='*')
+    picture = UploadedFileField(required=False, allow_null=True, allowed_types=(
+        'image/png', 'image/jpeg', 'image/gif'
+    ), max_size=10 * 1024 * 1024)
 
     class Meta:
         model = Item
@@ -123,7 +127,7 @@ class ItemSerializer(I18nAwareModelSerializer):
                   'min_per_order', 'max_per_order', 'checkin_attention', 'has_variations', 'variations',
                   'addons', 'bundles', 'original_price', 'require_approval', 'generate_tickets',
                   'show_quota_left', 'hidden_if_available', 'allow_waitinglist', 'issue_giftcard', 'meta_data')
-        read_only_fields = ('has_variations', 'picture')
+        read_only_fields = ('has_variations',)
 
     def validate(self, data):
         data = super().validate(data)