✨ Add JSON-compatible float constraints for NaN and Inf

docs/usage/model_config.md

@@ -121,6 +121,11 @@ not be included in the model schemas. **Note**: this means that attributes on th
 : whether stdlib dataclasses `__post_init__` should be run before (default behaviour with value `'before_validation'`)
   or after (value `'after_validation'`) parsing and validation when they are [converted](dataclasses.md#stdlib-dataclasses-and-_pydantic_-dataclasses).
 
+**`allow_inf_nan`**
+: whether to allows infinity (`+inf` an `-inf`) and NaN values to float fields, defaults to `True`,
+  set to `False` for compatibility with `JSON`,
+  see [#3994](https://github.com/pydantic/pydantic/pull/3994) for more details, added in **V1.10**
+
 ## Change behaviour globally
 
 If you wish to change the behaviour of _pydantic_ globally, you can create your own custom `BaseModel`

pydantic/config.py

@@ -67,6 +67,7 @@ class ConfigDict(TypedDict, total=False):
         json_dumps: AnyArgTCallable[str]
         json_encoders: Dict[Type[object], AnyCallable]
         underscore_attrs_are_private: bool
+        allow_inf_nan: bool
 
         # whether or not inherited models as fields should be reconstructed as base model
         copy_on_model_validation: bool
@@ -103,6 +104,7 @@ class BaseConfig:
     json_dumps: Callable[..., str] = json.dumps
     json_encoders: Dict[Union[Type[Any], str, ForwardRef], AnyCallable] = {}
     underscore_attrs_are_private: bool = False
+    allow_inf_nan: bool = True
 
     # whether inherited models as fields should be reconstructed as base model,
     # and whether such a copy should be shallow or deep

pydantic/types.py

@@ -294,8 +294,7 @@ def __get_validators__(cls) -> 'CallableGenerator':
         yield strict_float_validator if cls.strict else float_validator
         yield number_size_validator
         yield number_multiple_validator
-        if cls.allow_inf_nan is False:
-            yield float_finite_validator
+        yield float_finite_validator
 
 
 def confloat(
@@ -306,7 +305,7 @@ def confloat(
     lt: float = None,
     le: float = None,
     multiple_of: float = None,
-    allow_inf_nan: bool = True,
+    allow_inf_nan: Optional[bool] = None,
 ) -> Type[float]:
     # use kwargs then define conf in a dict to aid with IDE type hinting
     namespace = dict(strict=strict, gt=gt, ge=ge, lt=lt, le=le, multiple_of=multiple_of, allow_inf_nan=allow_inf_nan)
@@ -338,7 +337,7 @@ class StrictFloat(ConstrainedFloat):
         strict = True
 
     class FiniteFloat(ConstrainedFloat):
-        allow_info_nan = False
+        allow_inf_nan = False
 
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ BYTES TYPES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

pydantic/validators.py

@@ -152,8 +152,12 @@ def strict_float_validator(v: Any) -> float:
     raise errors.FloatError()
 
 
-def float_finite_validator(v: 'Number') -> 'Number':
-    if math.isnan(v) or math.isinf(v):
+def float_finite_validator(v: 'Number', field: 'ModelField', config: 'BaseConfig') -> 'Number':
+    allow_inf_nan = getattr(field.type_, 'allow_inf_nan', None)
+    if allow_inf_nan is None:
+        allow_inf_nan = config.allow_inf_nan
+
+    if allow_inf_nan is False and (math.isnan(v) or math.isinf(v)):
         raise errors.NumberNotFiniteError()
     return v
 
@@ -618,12 +622,13 @@ def typeddict_validator(values: 'TypedDict') -> Dict[str, Any]:  # type: ignore[
 
 
 class IfConfig:
-    def __init__(self, validator: AnyCallable, *config_attr_names: str) -> None:
+    def __init__(self, validator: AnyCallable, *config_attr_names: str, ignored_value: Any = False) -> None:
         self.validator = validator
         self.config_attr_names = config_attr_names
+        self.ignored_value = ignored_value
 
     def check(self, config: Type['BaseConfig']) -> bool:
-        return any(getattr(config, name) not in {None, False} for name in self.config_attr_names)
+        return any(getattr(config, name) not in {None, self.ignored_value} for name in self.config_attr_names)
 
 
 # order is important here, for example: bool is a subclass of int so has to come first, datetime before date same,
@@ -653,7 +658,7 @@ def check(self, config: Type['BaseConfig']) -> bool:
     ),
     (bool, [bool_validator]),
     (int, [int_validator]),
-    (float, [float_validator]),
+    (float, [float_validator, IfConfig(float_finite_validator, 'allow_inf_nan', ignored_value=True)]),
     (Path, [path_validator]),
     (datetime, [parse_datetime]),
     (date, [parse_date]),

tests/test_types.py

@@ -43,6 +43,7 @@
     EmailStr,
     Field,
     FilePath,
+    FiniteFloat,
     FutureDate,
     Json,
     NameEmail,
@@ -1571,6 +1572,9 @@ class Model(BaseModel):
     m = Model(a=5.1, b=-5.2, c=0, d=0, e=5.3, f=9.9, g=2.5, h=42)
     assert m.dict() == {'a': 5.1, 'b': -5.2, 'c': 0, 'd': 0, 'e': 5.3, 'f': 9.9, 'g': 2.5, 'h': 42}
 
+    assert Model(a=float('inf')).a == float('inf')
+    assert Model(b=float('-inf')).b == float('-inf')
+
     with pytest.raises(ValidationError) as exc_info:
         Model(a=-5.1, b=5.2, c=-5.1, d=5.1, e=-5.3, f=9.91, g=4.2, h=float('nan'))
     assert exc_info.value.errors() == [
@@ -1636,8 +1640,9 @@ class Model(BaseModel):
 @pytest.mark.parametrize('value', [float('inf'), float('-inf'), float('nan')])
 def test_finite_float_validation_error(value):
     class Model(BaseModel):
-        a: confloat(allow_inf_nan=False)
+        a: FiniteFloat
 
+    assert Model(a=42).a == 42
     with pytest.raises(ValidationError) as exc_info:
         Model(a=value)
     assert exc_info.value.errors() == [
@@ -1649,6 +1654,25 @@ class Model(BaseModel):
     ]
 
 
+def test_finite_float_config():
+    class Model(BaseModel):
+        a: float
+
+        class Config:
+            allow_inf_nan = False
+
+    assert Model(a=42).a == 42
+    with pytest.raises(ValidationError) as exc_info:
+        Model(a=float('nan'))
+    assert exc_info.value.errors() == [
+        {
+            'loc': ('a',),
+            'msg': 'ensure this value is a finite number',
+            'type': 'value_error.number.not_finite_number',
+        },
+    ]
+
+
 def test_strict_bytes():
     class Model(BaseModel):
         v: StrictBytes