Get rid of eval in metadata type default and lookup fields. gh-issue #151.

mayan/apps/metadata/classes.py

@@ -1,9 +1,8 @@
 from __future__ import unicode_literals
 
+from django.core.exceptions import ObjectDoesNotExist
 from django.utils.translation import ugettext_lazy as _
 
-from .models import MetadataType
-
 
 class DocumentMetadataHelper(object):
     @staticmethod
@@ -17,7 +16,35 @@ class DocumentMetadataHelper(object):
     def __getattr__(self, name):
         try:
             return self.instance.metadata.get(metadata_type__name=name).value
-        except MetadataType.DoesNotExist:
+        except ObjectDoesNotExist:
             raise AttributeError(
                 _('\'metadata\' object has no attribute \'%s\'') % name
             )
+
+
+class MetadataLookup(object):
+    _registry = []
+
+    @classmethod
+    def get_as_context(cls):
+        result = {}
+        for entry in cls._registry:
+            result[entry.name] = entry.value
+
+        return result
+
+    @classmethod
+    def get_as_help_text(cls):
+        result = []
+        for entry in cls._registry:
+            result.append(
+                '{{{{ {0} }}}} = "{1}"'.format(entry.name, entry.description)
+            )
+
+        return ' '.join(result)
+
+    def __init__(self, description, name, value):
+        self.description = description
+        self.name = name
+        self.value = value
+        self.__class__._registry.append(self)