Fix precondition on rename

The precondition was too strong. Loosen it just enough to make the function
useful in all the ways it should be without allowing bad cases through.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/clojure_sql/core.clj b/src/clojure_sql/core.clj
index 6cdb115..c829331 100644
--- a/src/clojure_sql/core.clj
+++ b/src/clojure_sql/core.clj
@@ -208,8 +208,10 @@
 
 (defn rename [query field-renames]
   {:pre [(map? field-renames)
+         ;; the intersection of the new aliases with the old aliases NOT renamed by this operation
          (empty? (set/intersection (set (vals field-renames))
-                                   (set (vals (:fields query)))))]}
+                                   (set/difference (set (vals (:fields query)))
+                                                   (set (keys field-renames)))))]}
   (let [fields (:fields query)
         alias-lookup (u/flip-map (:fields query)) 
         original-name (fn [field]
@@ -337,7 +339,8 @@
       deref)
   (-> (table :users)
       (project [:id :name])
-      (rename {:id :name})
+      (rename {:id :name
+               :name :id})
       deref)
 
   (-> (table :anotherStack)