Use the correct foreign key when sorting belongs_to associations (#1552)

Don't assume the foreign key will be ${FOO}_id.

Fixes #1182.

lib/administrate/order.rb

@@ -62,7 +62,7 @@ def order_by_count(relation)
     end
 
     def order_by_id(relation)
-      relation.reorder("#{attribute}_id #{direction}")
+      relation.reorder("#{foreign_key(relation)} #{direction}")
     end
 
     def has_many_attribute?(relation)
@@ -76,5 +76,9 @@ def belongs_to_attribute?(relation)
     def reflect_association(relation)
       relation.klass.reflect_on_association(attribute.to_s)
     end
+
+    def foreign_key(relation)
+      reflect_association(relation).foreign_key
+    end
   end
 end

spec/lib/administrate/order_spec.rb

@@ -73,12 +73,15 @@
     context "when relation has belongs_to association" do
       it "orders by id" do
         order = Administrate::Order.new(:name)
-        relation = relation_with_association(:belongs_to)
+        relation = relation_with_association(
+          :belongs_to,
+          foreign_key: "some_foreign_key",
+        )
         allow(relation).to receive(:reorder).and_return(relation)
 
         ordered = order.apply(relation)
 
-        expect(relation).to have_received(:reorder).with("name_id asc")
+        expect(relation).to have_received(:reorder).with("some_foreign_key asc")
         expect(ordered).to eq(relation)
       end
     end
@@ -176,9 +179,15 @@ def relation_with_column(column)
     )
   end
 
-  def relation_with_association(association)
+  def relation_with_association(association, foreign_key: "#{association}_id")
     double(
-      klass: double(reflect_on_association: double(macro: association)),
+      klass: double(
+        reflect_on_association: double(
+          "#{association}_reflection",
+          macro: association,
+          foreign_key: foreign_key,
+        ),
+      ),
     )
   end
 end