Do visit deduplication in our walk helpers

src/macaw/rewrite.clj

@@ -55,12 +55,10 @@
         replace-name (fn [->s]
                        (fn [acc ^ASTNodeAccess visitable]
                          (let [node (.getASTNode visitable)]
-                           ;; work around ast walker repeatedly visiting the same expressions (bug ?!)
-                           ;; also not sure why sometimes we get a phantom visitable without an underlying node
-                           (if (or (nil? node) (contains? @seen visitable))
+                           ;; not sure why sometimes we get a phantom visitable without an underlying node
+                           (if (nil? node)
                              acc
-                             (do (vswap! seen conj visitable)
-                                 (conj acc [(node->idx-range node sql) (->s visitable)]))))))]
+                             (conj acc [(node->idx-range node sql) (->s visitable)])))))]
     (splice-replacements
      sql
      (mw/fold-query

src/macaw/walk.clj

@@ -17,17 +17,26 @@
     (f v)
     acc))
 
+;; work around ast walker repeatedly visiting the same expressions (bug ?!)
+(defn- deduplicate-visits [f]
+  (let [seen (volatile! #{})]
+    (fn [acc visitable]
+      (if (contains? @seen visitable)
+        acc
+        (do (vswap! seen conj visitable)
+            (f acc visitable))))))
+
 (defn- update-keys-vals [m key-f val-f]
   (into {} (map (fn [[k v]] [(key-f k) (val-f v)])) m))
 
 (defn walk-query
   "Walk over the query's AST, using the callbacks for their side-effects, for example to mutate the AST itself."
   [parsed-query callbacks]
-  (let [callbacks (update-keys-vals callbacks ->callback-key preserve)]
+  (let [callbacks (update-keys-vals callbacks ->callback-key (comp deduplicate-visits preserve))]
     (.walk (AstWalker. callbacks ::ignored) parsed-query)))
 
 (defn fold-query
   "Fold over the query's AST, using the callbacks to update the accumulator."
   [parsed-query callbacks init-val]
-  (let [callbacks (update-keys callbacks ->callback-key)]
+  (let [callbacks (update-keys-vals callbacks ->callback-key deduplicate-visits)]
     (.fold (AstWalker. callbacks init-val) parsed-query)))