fix: DecimalField no longer raises InvalidOperation for values over 28 digits

CHANGELOG.rst

@@ -15,6 +15,10 @@ Added
 ^^^^^
 - Support forward relation ``in`` and ``not_in`` filters with model instances. (#2323)
 
+Fixed
+^^^^^
+- ``DecimalField`` no longer raises ``decimal.InvalidOperation`` for values with more than 28 significant digits. (#2349)
+
 1.1.9
 -----
 

tests/fields/test_decimal.py

@@ -1,4 +1,4 @@
-from decimal import Decimal
+from decimal import ROUND_HALF_UP, Decimal, InvalidOperation, localcontext
 
 import pytest
 
@@ -340,3 +340,33 @@ def test_to_python_value_scale():
     field0 = fields.DecimalField(max_digits=12, decimal_places=0)
     assert str(field0.to_python_value("10")) == "10"
     assert str(field0.to_python_value("100")) == "100"
+
+
+def test_to_python_value_high_precision():
+    field = fields.DecimalField(max_digits=40, decimal_places=10)
+    assert field.to_python_value("123456789012345678901234567890.5") == Decimal(
+        "123456789012345678901234567890.5000000000"
+    )
+    field = fields.DecimalField(max_digits=30, decimal_places=2)
+    assert field.to_python_value("1234567890123456789012345678.50") == Decimal(
+        "1234567890123456789012345678.50"
+    )
+
+
+def test_to_python_value_high_precision_boundaries():
+    field = fields.DecimalField(max_digits=28, decimal_places=0)
+    assert field.to_python_value("1" * 28) == Decimal("1" * 28)
+
+    field = fields.DecimalField(max_digits=30, decimal_places=2)
+    with pytest.raises(InvalidOperation):
+        field.to_python_value("1" * 31)
+
+    field = fields.DecimalField(max_digits="40", decimal_places=10)
+    assert field.to_python_value("1" * 30) == Decimal("1" * 30 + ".0000000000")
+
+
+def test_to_python_value_keeps_context_rounding():
+    field = fields.DecimalField(max_digits=5, decimal_places=2)
+    with localcontext() as ctx:
+        ctx.rounding = ROUND_HALF_UP
+        assert str(field.to_python_value("1.005")) == "1.01"

tortoise/fields/data.py

@@ -6,7 +6,7 @@
 import json
 import warnings
 from collections.abc import Callable
-from decimal import Decimal
+from decimal import Decimal, InvalidOperation, getcontext
 from enum import Enum, IntEnum
 from typing import TYPE_CHECKING, Any, Literal, TypeVar, overload
 from uuid import UUID, uuid4
@@ -32,7 +32,7 @@
     from pydantic import BaseModel as _PydanticBaseModel
     from pydantic._internal._model_construction import ModelMetaclass as _PydanticModelMetaclass
 except ImportError:
-    _PydanticBaseModel = None  # type: ignore
+    _PydanticBaseModel = None  # type: ignore[assignment,misc]
     _PydanticModelMetaclass = None  # type: ignore[assignment,misc]
 
 if TYPE_CHECKING:  # pragma: nocoverage
@@ -380,10 +380,22 @@ def __init__(self, max_digits: int, decimal_places: int, **kwargs: Any) -> None:
         self.decimal_places = decimal_places
         self.quant = Decimal("1" if decimal_places == 0 else f"1.{('0' * decimal_places)}")
 
+    @overload
+    def to_python_value(self, value: None) -> None: ...
+
+    @overload
+    def to_python_value(self, value: Any) -> Decimal: ...
+
     def to_python_value(self, value: Any) -> Decimal | None:
-        if value is not None:
-            value = Decimal(value).quantize(self.quant)
-        return value
+        if value is None:
+            return None
+        d = Decimal(value)
+        try:
+            return d.quantize(self.quant)
+        except InvalidOperation:
+            context = getcontext().copy()
+            context.prec = max(context.prec, int(self.max_digits))
+            return d.quantize(self.quant, context=context)
 
     @property
     def SQL_TYPE(self) -> str:  # type: ignore[override]
@@ -681,7 +693,6 @@ def to_db_value(
         self, value: datetime.timedelta | None, instance: type[Model] | Model
     ) -> int | None:
         self.validate(value)
-
         if value is None:
             return None
         return (value.days * 86400000000) + (value.seconds * 1000000) + value.microseconds
@@ -899,7 +910,7 @@ def __init__(
 
         # Automatic description for the field if not specified by the user
         if description is None:
-            description = "\n".join([f"{e.name}: {int(e.value)}" for e in enum_type])[:2048]
+            description = "\n".join(f"{e.name}: {int(e.value)}" for e in enum_type)[:2048]
 
         super().__init__(description=description, **kwargs)
         self.enum_type = enum_type
@@ -955,14 +966,11 @@ def __init__(
     ) -> None:
         # Automatic description for the field if not specified by the user
         if description is None:
-            description = "\n".join([f"{e.name}: {str(e.value)}" for e in enum_type])[:2048]
+            description = "\n".join(f"{e.name}: {e.value!s}" for e in enum_type)[:2048]
 
         # Automatic CharField max_length
         if max_length == 0:
-            for item in enum_type:
-                item_len = len(str(item.value))
-                if item_len > max_length:
-                    max_length = item_len
+            max_length = max((len(str(i.value)) for i in enum_type), default=0)
 
         super().__init__(description=description, max_length=max_length, **kwargs)
         self.enum_type = enum_type