New type StrLimited

changes/2104-lucastosetto.md

@@ -0,0 +1 @@
+Added simplified length limited string type, declared as `StrLimited[max_length]`.

pydantic/__init__.py

@@ -73,6 +73,7 @@
     'NoneStr',
     'NoneBytes',
     'StrBytes',
+    'StrLimited',
     'NoneStrBytes',
     'StrictStr',
     'ConstrainedBytes',

pydantic/types.py

@@ -97,6 +97,7 @@
     'StrictBytes',
     'StrictInt',
     'StrictFloat',
+    'StrLimited',
     'PaymentCardNumber',
     'ByteSize',
     'PastDate',
@@ -436,6 +437,12 @@ def constr(
     return _registered(type('ConstrainedStrValue', (ConstrainedStr,), namespace))
 
 
+class StrLimited:
+    @classmethod
+    def __class_getitem__(cls, max_length: int) -> Type[ConstrainedStr]:
+        return constr(max_length=max_length, strip_whitespace=True)
+
+
 if TYPE_CHECKING:
     StrictStr = str
 else:

tests/test_types.py

@@ -61,6 +61,7 @@
     StrictFloat,
     StrictInt,
     StrictStr,
+    StrLimited,
     ValidationError,
     conbytes,
     condecimal,
@@ -733,6 +734,34 @@ class Model(BaseModel):
     ]
 
 
+def test_str_limited_good():
+    max_length = 5
+
+    class Model(BaseModel):
+        v: StrLimited[5]
+
+    m = Model(v='abcde ')
+    assert m.v == 'abcde'
+
+
+def test_str_limited_too_long():
+    max_length = 5
+
+    class Model(BaseModel):
+        v: StrLimited[5]
+
+    with pytest.raises(ValidationError) as exc_info:
+        Model(v='abcdef')
+    assert exc_info.value.errors() == [
+        {
+            'loc': ('v',),
+            'msg': f'ensure this value has at most {max_length} characters',
+            'type': 'value_error.any_str.max_length',
+            'ctx': {'limit_value': max_length},
+        }
+    ]
+
+
 def test_module_import():
     class PyObjectModel(BaseModel):
         module: PyObject = 'os.path'