Refactor some common FormEncode validators, plus add some more

tailbone/forms/validators.py

@@ -2,7 +2,7 @@
 ################################################################################
 #
 #  Rattail -- Retail Software Framework
-#  Copyright © 2010-2015 Lance Edgar
+#  Copyright © 2010-2016 Lance Edgar
 #
 #  This file is part of Rattail.
 #
@@ -24,53 +24,70 @@
 Custom FormEncode Validators
 """
 
-from __future__ import unicode_literals
+from __future__ import unicode_literals, absolute_import
 
 from rattail.db import model
 
-import formencode
-from formencode import validators
+import formencode as fe
 
 from tailbone.db import Session
 
 
-class ValidCustomer(validators.FancyValidator):
+class ModelValidator(fe.validators.FancyValidator):
+    """
+    Generic validator for data model reference fields.
+    """
+    model_class = None
+
+    @property
+    def model_name(self):
+        self.model_class.__name__
+
+    def _to_python(self, value, state):
+        if value:
+            obj = Session.query(self.model_class).get(value)
+            if obj:
+                return obj
+            raise formencode.Invalid("{} not found".format(self.model_name), value, state)
+
+
+class ValidStore(ModelValidator):
+    """
+    Validator for store field.
+    """
+    model_class = model.Store
+
+
+class ValidCustomer(ModelValidator):
     """
     Validator for customer field.
     """
-
-    def _to_python(self, value, state):
-        if not value:
-            return None
-        customer = Session.query(model.Customer).get(value)
-        if not customer:
-            raise formencode.Invalid("Customer not found", value, state)
-        return customer
+    model_class = model.Customer
 
 
-class ValidProduct(validators.FancyValidator):
+class ValidDepartment(ModelValidator):
+    """
+    Validator for department field.
+    """
+    model_class = model.Department
+
+
+class ValidEmployee(ModelValidator):
+    """
+    Validator for employee field.
+    """
+    model_class = model.Employee
+
+
+class ValidProduct(ModelValidator):
     """
     Validator for product field.
     """
-
-    def _to_python(self, value, state):
-        if not value:
-            return None
-        product = Session.query(model.Product).get(value)
-        if not product:
-            raise formencode.Invalid("Product not found", value, state)
-        return product
+    model_class = model.Product
 
 
-class ValidUser(validators.FancyValidator):
+class ValidUser(ModelValidator):
     """
-    Validator for product field.
+    Validator for user field.
     """
-
-    def to_python(self, value, state):
-        if not value:
-            return None
-        user = Session.query(model.User).get(value)
-        if not user:
-            raise formencode.Invalid("User not found.", value, state)
-        return user
+    model_class = model.User