fix: allow to query decimal fields with int (#2838)

* fix: allow to query decimal fields with int

Django allow to query decimal fields with int, and given there should be no precision loss, we should accept ints to query such fields.

Note: even though we do accept floats when setting a value in a decimal field, I opted for only accepting ints in this PR, as to minimize the impact of the change.

Fixes #2831.

Co-authored-by: Sebastian Kreft <911768+sk-@users.noreply.github.com>
Co-authored-by: sobolevn <mail@sobolevn.me>

Author: sk-

django-stubs/db/models/fields/__init__.pyi

@@ -263,7 +263,7 @@ class FloatField(Field[_ST, _GT]):
 class DecimalField(Field[_ST, _GT]):
     _pyi_private_set_type: str | float | decimal.Decimal | Combinable
     _pyi_private_get_type: decimal.Decimal
-    _pyi_lookup_exact_type: str | decimal.Decimal
+    _pyi_lookup_exact_type: str | int | decimal.Decimal
     # attributes
     max_digits: int
     decimal_places: int

tests/typecheck/managers/querysets/test_filter.yml

@@ -45,6 +45,26 @@
                 class User(models.Model):
                     age = models.IntegerField()
 
+# Regression test for #2831
+-   case: filter_with_decimal
+    main: |
+        from myapp.models import MyModel
+        from decimal import Decimal
+
+        MyModel.objects.filter(a=1)
+        MyModel.objects.filter(a="1.0")
+        MyModel.objects.filter(a=Decimal(1.0))
+        MyModel.objects.filter(a=1.0)  # E: Incompatible type for lookup 'a': (got "float", expected "str | int | Decimal")  [misc]
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+
+                class MyModel(models.Model):
+                    a = models.DecimalField()
 
 -   case: filter_with_multiple_fields
     main: |