Add lenght validator

Author: WaVEV

django_mongodb_backend/fields/array.py

@@ -10,6 +10,7 @@
 from ..forms import SimpleArrayField
 from ..query_utils import process_lhs, process_rhs
 from ..utils import prefix_validation_error
+from .validators import LengthValidator
 
 __all__ = ["ArrayField"]
 
@@ -27,14 +28,23 @@ class ArrayField(CheckFieldDefaultMixin, Field):
     }
     _default_hint = ("list", "[]")
 
-    def __init__(self, base_field, size=None, **kwargs):
+    def __init__(self, base_field, size=None, fixed_size=None, **kwargs):
         self.base_field = base_field
         self.size = size
+        self.fixed_size = fixed_size
+        if fixed_size and size:
+            raise ValueError("Cannot define both, size and fixed_size")
+
         if self.size:
             self.default_validators = [
                 *self.default_validators,
                 ArrayMaxLengthValidator(self.size),
             ]
+        if self.fixed_size:
+            self.default_validators = [
+                *self.default_validators,
+                LengthValidator(self.fixed_size),
+            ]
         # For performance, only add a from_db_value() method if the base field
         # implements it.
         if hasattr(self.base_field, "from_db_value"):

django_mongodb_backend/fields/validators.py

@@ -0,0 +1,19 @@
+from django.core.validators import BaseValidator
+from django.utils.deconstruct import deconstructible
+from django.utils.translation import ngettext_lazy
+
+
+@deconstructible
+class LengthValidator(BaseValidator):
+    message = ngettext_lazy(
+        "List contains %(show_value)d item, it should contain %(limit_value)d.",
+        "List contains %(show_value)d items, it should contain %(limit_value)d.",
+        "show_value",
+    )
+    code = "length"
+
+    def compare(self, a, b):
+        return a == b
+
+    def clean(self, x):
+        return len(x)