fix: constraints with a Falsy value should still return a truthful ha…

…s_constraints (#1844)

datamodel_code_generator/model/base.py

@@ -63,7 +63,7 @@ class Config:
 
     @cached_property
     def has_constraints(self) -> bool:
-        return any(v for v in self.dict().values() if v is not None)
+        return any(v is not None for v in self.dict().values())
 
     @staticmethod
     def merge_constraints(

tests/model/pydantic/test_constraint.py

@@ -0,0 +1,21 @@
+from typing import Optional, Union
+
+import pytest
+
+from datamodel_code_generator.model.pydantic.base_model import Constraints
+from datamodel_code_generator.types import UnionIntFloat
+
+
+@pytest.mark.parametrize(
+    'gt,expected',
+    [
+        (None, False),
+        (4, True),
+        (0, True),
+        (0.0, True),
+    ],
+)
+def test_constraint(gt: Optional[Union[int, float]], expected: bool) -> None:
+    constraints = Constraints()
+    constraints.gt = UnionIntFloat(gt) if gt is not None else None
+    assert constraints.has_constraints == expected