API: Expose TaxRule.custom_rules (#3426)

src/pretix/api/serializers/__init__.py

@@ -19,6 +19,8 @@
 # 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/>.
 #
+import json
+
 from rest_framework import serializers
 
 
@@ -46,3 +48,16 @@ class AsymmetricField(serializers.Field):
 
     def run_validation(self, data=serializers.empty):
         return self.write.run_validation(data)
+
+
+class CompatibleJSONField(serializers.JSONField):
+    def to_internal_value(self, data):
+        try:
+            return json.dumps(data)
+        except (TypeError, ValueError):
+            self.fail('invalid')
+
+    def to_representation(self, value):
+        if value:
+            return json.loads(value)
+        return value

src/pretix/api/serializers/event.py

@@ -46,6 +46,7 @@ from rest_framework import serializers
 from rest_framework.fields import ChoiceField, Field
 from rest_framework.relations import SlugRelatedField
 
+from pretix.api.serializers import CompatibleJSONField
 from pretix.api.serializers.i18n import I18nAwareModelSerializer
 from pretix.api.serializers.settings import SettingsSerializer
 from pretix.base.models import Device, Event, TaxRule, TeamAPIToken
@@ -53,6 +54,7 @@ from pretix.base.models.event import SubEvent
 from pretix.base.models.items import (
     ItemMetaProperty, SubEventItem, SubEventItemVariation,
 )
+from pretix.base.models.tax import CustomRulesValidator
 from pretix.base.services.seating import (
     SeatProtected, generate_seats, validate_plan_change,
 )
@@ -650,9 +652,16 @@ class SubEventSerializer(I18nAwareModelSerializer):
 
 
 class TaxRuleSerializer(CountryFieldMixin, I18nAwareModelSerializer):
+    custom_rules = CompatibleJSONField(
+        validators=[CustomRulesValidator()],
+        required=False,
+        allow_null=True,
+    )
+
     class Meta:
         model = TaxRule
-        fields = ('id', 'name', 'rate', 'price_includes_tax', 'eu_reverse_charge', 'home_country', 'internal_name', 'keep_gross_if_rate_changes')
+        fields = ('id', 'name', 'rate', 'price_includes_tax', 'eu_reverse_charge', 'home_country', 'internal_name',
+                  'keep_gross_if_rate_changes', 'custom_rules')
 
 
 class EventSettingsSerializer(SettingsSerializer):

src/pretix/api/serializers/order.py

@@ -19,7 +19,6 @@
 # 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/>.
 #
-import json
 import logging
 import os
 from collections import Counter, defaultdict
@@ -39,6 +38,7 @@ from rest_framework.exceptions import ValidationError
 from rest_framework.relations import SlugRelatedField
 from rest_framework.reverse import reverse
 
+from pretix.api.serializers import CompatibleJSONField
 from pretix.api.serializers.event import SubEventSerializer
 from pretix.api.serializers.i18n import I18nAwareModelSerializer
 from pretix.api.serializers.item import (
@@ -896,19 +896,6 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
         return data
 
 
-class CompatibleJSONField(serializers.JSONField):
-    def to_internal_value(self, data):
-        try:
-            return json.dumps(data)
-        except (TypeError, ValueError):
-            self.fail('invalid')
-
-    def to_representation(self, value):
-        if value:
-            return json.loads(value)
-        return value
-
-
 class WrappedList:
     def __init__(self, data):
         self._data = data