revamp walk/1

Resolves jqlang#2584; see also jqlang#2611

src/builtin.jq

@@ -249,17 +249,18 @@ def bsearch($target):
       else .[2]
       end
   end;
-
+#
 # Apply f to composite entities recursively, and to atoms
 def walk(f):
-  . as $in
-  | if type == "object" then
-      reduce keys_unsorted[] as $key
-        ( {}; . + { ($key):  ($in[$key] | walk(f)) } ) | f
-  elif type == "array" then map( walk(f) ) | f
-  else f
-  end;
-
+  def w:
+    if type == "object"
+    then map_values(w)
+    elif type == "array" then map(w)
+    else .
+    end
+    | f;
+  w;
+#
 # SQL-ish operators here:
 def INDEX(stream; idx_expr):
   reduce stream as $row ({}; .[$row|idx_expr|tostring] = $row);

tests/jq.test

@@ -1744,3 +1744,7 @@ false
 1
 1
 
+# Issue #2584
+walk(select(IN({}, []) | not))
+{"a":1,"b":[]}
+{"a":1}