Add a JSON and YAML validator to the common app

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/common/validators.py

@@ -1,9 +1,18 @@
 from __future__ import unicode_literals
 
+import json
 import re
+import yaml
 
+try:
+    from yaml import CSafeLoader as SafeLoader
+except ImportError:
+    from yaml import SafeLoader
+
+from django.core.exceptions import ValidationError
 from django.core.validators import RegexValidator
 from django.utils import six
+from django.utils.deconstruct import deconstructible
 from django.utils.functional import SimpleLazyObject
 from django.utils.translation import ugettext_lazy as _
 
@@ -23,6 +32,54 @@ def _lazy_re_compile(regex, flags=0):
     return SimpleLazyObject(_compile)
 
 
+@deconstructible
+class JSONValidator(object):
+    """
+    Validates that the input is JSON compliant.
+    """
+    def __call__(self, value):
+        value = value.strip()
+        try:
+            json.loads(stream=value)
+        except ValueError:
+            raise ValidationError(
+                _('Enter a valid JSON value.'),
+                code='invalid'
+            )
+
+    def __eq__(self, other):
+        return (
+            isinstance(other, JSONValidator)
+        )
+
+    def __ne__(self, other):
+        return not (self == other)
+
+
+@deconstructible
+class YAMLValidator(object):
+    """
+    Validates that the input is YAML compliant.
+    """
+    def __call__(self, value):
+        value = value.strip()
+        try:
+            yaml.load(stream=value, Loader=SafeLoader)
+        except yaml.error.YAMLError:
+            raise ValidationError(
+                _('Enter a valid YAML value.'),
+                code='invalid'
+            )
+
+    def __eq__(self, other):
+        return (
+            isinstance(other, YAMLValidator)
+        )
+
+    def __ne__(self, other):
+        return not (self == other)
+
+
 internal_name_re = _lazy_re_compile(r'^[a-zA-Z0-9_]+\Z')
 validate_internal_name = RegexValidator(
     internal_name_re, _(