🐛 fix for floating point multiple_of values

 - modulo doesn't work with floating point values in many cases, e.g. `0.3 % 0.1 == 0.09999999999999998`
 - port implementation from: tdegrunt/jsonschema#187 (comment)
 - add tests for int/float multiple_of values

pydantic/validators.py

@@ -121,8 +121,14 @@ def float_validator(v: Any) -> float:
 
 def number_multiple_validator(v: 'Number', field: 'Field') -> 'Number':
     field_type: ConstrainedNumber = field.type_  # type: ignore
-    if field_type.multiple_of is not None and v % field_type.multiple_of != 0:  # type: ignore
-        raise errors.NumberNotMultipleError(multiple_of=field_type.multiple_of)
+    if field_type.multiple_of is not None:
+        v_places = abs(Decimal(str(v)).as_tuple().exponent)
+        schema_places = abs(Decimal(str(field_type.multiple_of)).as_tuple().exponent)
+        max_places = max(v_places, schema_places)
+        multiplier = 10 ** max_places
+        remainder = round(v * multiplier) % round(field_type.multiple_of * multiplier)
+        if remainder != 0:
+            raise errors.NumberNotMultipleError(multiple_of=field_type.multiple_of)
 
     return v
 

tests/test_types.py

@@ -1422,16 +1422,34 @@ class Model(BaseModel):
         Model(a=6)
 
 
-def test_number_multiple_of():
+@pytest.mark.parametrize('value,is_valid', ((10, True), (1337, False), (23, False), (100, True), (20, True)))
+def test_number_multiple_of(value, is_valid):
     class Model(BaseModel):
         a: conint(multiple_of=5)
 
-    assert Model(a=10).dict() == {'a': 10}
+    if is_valid:
+        assert Model(a=value).dict() == {'a': value}
+    else:
+        multiple_message = base_message.replace('limit_value', 'multiple_of')
+        message = multiple_message.format(msg='a multiple of 5', ty='multiple', value=5)
+        with pytest.raises(ValidationError, match=message):
+            Model(a=value)
 
-    multiple_message = base_message.replace('limit_value', 'multiple_of')
-    message = multiple_message.format(msg='a multiple of 5', ty='multiple', value=5)
-    with pytest.raises(ValidationError, match=message):
-        Model(a=42)
+
+@pytest.mark.parametrize(
+    'value,is_valid', ((0.2, True), (0.3, True), (0.4, True), (0.5, True), (0.07, False), (1.27, False), (1, True))
+)
+def test_number_multiple_of_float(value, is_valid):
+    class Model(BaseModel):
+        a: confloat(multiple_of=0.1)
+
+    if is_valid:
+        assert Model(a=value).dict() == {'a': value}
+    else:
+        multiple_message = base_message.replace('limit_value', 'multiple_of')
+        message = multiple_message.format(msg='a multiple of 0.1', ty='multiple', value=0.1)
+        with pytest.raises(ValidationError, match=message):
+            Model(a=value)
 
 
 @pytest.mark.parametrize('fn', [conint, confloat, condecimal])