Merge pull request #117 from joliss/computed-attributes

Make schema not crash on computed attributes & associations

lib/active_model/serializer.rb

@@ -169,16 +169,31 @@ module ActiveModel
         klass = model_class
         columns = klass.columns_hash
 
-        attrs = _attributes.inject({}) do |hash, (name,key)|
-          column = columns[name.to_s]
-          hash.merge key => column.type
+        attrs = {}
+        _attributes.each do |name, key|
+          if column = columns[name.to_s]
+            attrs[key] = column.type
+          else
+            # Computed attribute (method on serializer or model). We cannot
+            # infer the type, so we put nil.
+            attrs[key] = nil
+          end
         end
 
-        associations = _associations.inject({}) do |hash, (attr,association_class)|
+        associations = {}
+        _associations.each do |attr, association_class|
           association = association_class.new(attr, self)
 
-          model_association = klass.reflect_on_association(association.name)
-          hash.merge association.key => { model_association.macro => model_association.name }
+          if model_association = klass.reflect_on_association(association.name)
+            # Real association.
+            associations[association.key] = { model_association.macro => model_association.name }
+          else
+            # Computed association. We could infer has_many vs. has_one from
+            # the association class, but that would make it different from
+            # real associations, which read has_one vs. belongs_to from the
+            # model.
+            associations[association.key] = nil
+          end
         end
 
         { :attributes => attrs, :associations => associations }