Allow more decimal places for tax rates (#6092)

* Allow more decimal places for tax rates

* Fix normalization

* More tax rate handling

* Add uncommitted tests

* Rebase migration

* Update src/pretix/base/migrations/0304_tax_rate_decimals.py

Co-authored-by: robbi5 <richt@rami.io>

---------

Co-authored-by: robbi5 <richt@rami.io>

src/pretix/base/models/invoices.py

@@ -49,6 +49,7 @@ from django_scopes import ScopedManager
 
 from pretix.base.settings import COUNTRIES_WITH_STATE_IN_ADDRESS
 from pretix.helpers.countries import FastCountryField
+from pretix.helpers.models import NormalizedDecimalField
 
 
 def invoice_filename(instance, filename: str) -> str:
@@ -450,7 +451,7 @@ class InvoiceLine(models.Model):
     description = models.TextField()
     gross_value = models.DecimalField(max_digits=13, decimal_places=2)
     tax_value = models.DecimalField(max_digits=13, decimal_places=2, default=Decimal('0.00'))
-    tax_rate = models.DecimalField(max_digits=7, decimal_places=2, default=Decimal('0.00'))
+    tax_rate = NormalizedDecimalField(max_digits=7, decimal_places=4, default=Decimal('0'))
     tax_name = models.CharField(max_length=190)
     tax_code = models.CharField(max_length=190, null=True, blank=True)
     subevent = models.ForeignKey('SubEvent', null=True, blank=True, on_delete=models.PROTECT)

src/pretix/base/models/orders.py

@@ -87,6 +87,7 @@ from pretix.base.timemachine import time_machine_now
 
 from ...helpers import OF_SELF
 from ...helpers.countries import CachedCountries, FastCountryField
+from ...helpers.models import NormalizedDecimalField
 from ...helpers.names import build_name
 from ...testutils.middleware import debugflags_var
 from ._transactions import (
@@ -2354,8 +2355,8 @@ class OrderFee(RoundingCorrectionMixin, models.Model):
     )
     description = models.CharField(max_length=190, blank=True)
     internal_type = models.CharField(max_length=255, blank=True)
-    tax_rate = models.DecimalField(
-        max_digits=7, decimal_places=2,
+    tax_rate = NormalizedDecimalField(
+        max_digits=7, decimal_places=4,
         verbose_name=_('Tax rate')
     )
     tax_rule = models.ForeignKey(
@@ -2551,8 +2552,8 @@ class OrderPosition(AbstractPosition):
         max_digits=13, decimal_places=2, null=True, blank=True,
     )
 
-    tax_rate = models.DecimalField(
-        max_digits=7, decimal_places=2,
+    tax_rate = NormalizedDecimalField(
+        max_digits=7, decimal_places=4,
         verbose_name=_('Tax rate')
     )
     tax_rule = models.ForeignKey(
@@ -3070,8 +3071,8 @@ class Transaction(models.Model):
     price_includes_rounding_correction = models.DecimalField(
         max_digits=13, decimal_places=2, default=Decimal("0.00")
     )
-    tax_rate = models.DecimalField(
-        max_digits=7, decimal_places=2,
+    tax_rate = NormalizedDecimalField(
+        max_digits=7, decimal_places=4,
         verbose_name=_('Tax rate')
     )
     tax_rule = models.ForeignKey(
@@ -3186,8 +3187,8 @@ class CartPosition(AbstractPosition):
         verbose_name=_("Limit for extending expiration date"),
         null=True
     )
-    tax_rate = models.DecimalField(
-        max_digits=7, decimal_places=2, default=Decimal('0.00'),
+    tax_rate = NormalizedDecimalField(
+        max_digits=7, decimal_places=4, default=Decimal('0'),
         verbose_name=_('Tax rate')
     )
     tax_code = models.CharField(

src/pretix/base/models/tax.py

@@ -40,6 +40,7 @@ from pretix.base.decimal import round_decimal
 from pretix.base.models.base import LoggedModel
 from pretix.base.templatetags.money import money_filter
 from pretix.helpers.countries import FastCountryField
+from pretix.helpers.models import NormalizedDecimalField
 
 
 class TaxedPrice:
@@ -335,9 +336,9 @@ class TaxRule(LoggedModel):
         max_length=190,
         choices=TAX_CODE_LISTS,
     )
-    rate = models.DecimalField(
-        max_digits=10,
-        decimal_places=2,
+    rate = NormalizedDecimalField(
+        max_digits=7,
+        decimal_places=4,
         validators=[
             MaxValueValidator(
                 limit_value=Decimal("100.00"),