Add validate.And (#1777)

* Add validate.And

* Rename _validate_callable to _validate_all

* Test composing And

* Add and_; fix passing a generator to And

* Remove and_

CHANGELOG.rst

@@ -6,6 +6,8 @@ Changelog
 
 Features:
 
+- Add ``validate.And`` (:issue:`1768`).
+  Thanks :user:`rugleb` for the suggestion.
 - Let ``Field``s be accessed by name as ``Schema`` attributes (:pr:`1631`).
 - Add a `NoDuplicates` validator in ``marshmallow.validate`` (:pr:`1793`).
 

src/marshmallow/fields.py

@@ -25,7 +25,7 @@
     StringNotCollectionError,
     FieldInstanceResolutionError,
 )
-from marshmallow.validate import Validator, Length
+from marshmallow.validate import And, Length
 from marshmallow.warnings import RemovedInMarshmallow4Warning
 
 __all__ = [
@@ -242,21 +242,11 @@ def _validate(self, value):
         """Perform validation on ``value``. Raise a :exc:`ValidationError` if validation
         does not succeed.
         """
-        errors = []
-        kwargs = {}
-        for validator in self.validators:
-            try:
-                r = validator(value)
-                if not isinstance(validator, Validator) and r is False:
-                    raise self.make_error("validator_failed")
-            except ValidationError as err:
-                kwargs.update(err.kwargs)
-                if isinstance(err.messages, dict):
-                    errors.append(err.messages)
-                else:
-                    errors.extend(err.messages)
-        if errors:
-            raise ValidationError(errors, **kwargs)
+        self._validate_all(value)
+
+    @property
+    def _validate_all(self):
+        return And(*self.validators, error=self.error_messages["validator_failed"])
 
     def make_error(self, key: str, **kwargs) -> ValidationError:
         """Helper method to make a `ValidationError` with an error message

src/marshmallow/types.py

@@ -8,3 +8,4 @@
 
 StrSequenceOrSet = typing.Union[typing.Sequence[str], typing.Set[str]]
 Tag = typing.Union[str, typing.Tuple[str, bool]]
+Validator = typing.Callable[[typing.Any], typing.Any]

src/marshmallow/validate.py

@@ -40,6 +40,56 @@ def __call__(self, value: typing.Any) -> typing.Any:
         ...
 
 
+class And(Validator):
+    """Compose multiple validators and combine their error messages.
+
+    Example: ::
+
+        from marshmallow import validate, ValidationError
+
+        def is_even(value):
+            if value % 2 != 0:
+                raise ValidationError("Not an even value.")
+
+        validator = validate.And(validate.Range(min=0), is_even)
+        validator(-1)
+        # ValidationError: ['Must be greater than or equal to 0.', 'Not an even value.']
+
+    :param validators: Validators to combine.
+    :param error: Error message to use when a validator returns ``False``.
+    """
+
+    default_error_message = "Invalid value."
+
+    def __init__(
+        self, *validators: types.Validator, error: typing.Optional[str] = None
+    ):
+        self.validators = tuple(validators)
+        self.error = error or self.default_error_message  # type: str
+
+    def _repr_args(self) -> str:
+        return "validators={!r}".format(self.validators)
+
+    def __call__(self, value: typing.Any) -> typing.Any:
+        errors = []
+        kwargs = {}
+        for validator in self.validators:
+            try:
+                r = validator(value)
+                if not isinstance(validator, Validator) and r is False:
+                    raise ValidationError(self.error)
+            except ValidationError as err:
+                kwargs.update(err.kwargs)
+                if isinstance(err.messages, dict):
+                    errors.append(err.messages)
+                else:
+                    # FIXME : Get rid of cast
+                    errors.extend(typing.cast(list, err.messages))
+        if errors:
+            raise ValidationError(errors, **kwargs)
+        return value
+
+
 class URL(Validator):
     """Validate a URL.
 

tests/test_deserialization.py

@@ -823,6 +823,11 @@ def test_email_field_deserialization(self):
             field.deserialize("invalidemail")
         assert excinfo.value.args[0][0] == "Not a valid email address."
 
+        field = fields.Email(validate=[validate.Length(min=12)])
+        with pytest.raises(ValidationError) as excinfo:
+            field.deserialize("[email protected]")
+        assert excinfo.value.args[0][0] == "Shorter than minimum length 12."
+
     # regression test for https://github.com/marshmallow-code/marshmallow/issues/1400
     def test_email_field_non_list_validators(self):
         field = fields.Email(validate=(validate.Length(min=9),))

tests/test_validate.py

@@ -892,6 +892,28 @@ def test_containsnoneof_mixing_types():
         validate.ContainsNoneOf([1, 2, 3])((1,))
 
 
+def is_even(value):
+    if value % 2 != 0:
+        raise ValidationError("Not an even value.")
+
+
+def test_and():
+    validator = validate.And(validate.Range(min=0), is_even)
+    assert validator(2)
+    with pytest.raises(ValidationError) as excinfo:
+        validator(-1)
+    errors = excinfo.value.messages
+    assert errors == ["Must be greater than or equal to 0.", "Not an even value."]
+
+    validator_with_composition = validate.And(validator, validate.Range(max=6))
+    assert validator_with_composition(4)
+    with pytest.raises(ValidationError) as excinfo:
+        validator_with_composition(7)
+
+    errors = excinfo.value.messages
+    assert errors == ["Not an even value.", "Must be less than or equal to 6."]
+
+
 def test_noduplicates():
     class Mock:
         def __init__(self, name):