Correctly print subshells nested in a variable expansion

libdash/printer.py

@@ -393,7 +393,14 @@ def string_of_arg_char (c, quote_mode=UNQUOTED):
     elif (type == "Q"):
         return "\"" + string_of_arg (param, quote_mode=QUOTED) + "\"";
     elif (type == "B"):
-        return "$(" + to_string (param) + ")";
+        body = to_string (param)
+        # to handle $( () )
+        try:
+            if body[0] == "(" and body[-1] == ")":
+                body = f" {body} "
+        except IndexError:
+            pass
+        return "$(" + body + ")"
     else:
         abort ();
 

ocaml/ast.ml

@@ -462,8 +462,12 @@ and string_of_arg_char ?quote_mode:(quote_mode=QUnquoted) = function
   | V (vt,nul,name,a) ->
      "${" ^ name ^ (if nul then ":" else "") ^ string_of_var_type vt ^ string_of_arg ~quote_mode a ^ "}"
   | Q a -> "\"" ^ string_of_arg ~quote_mode:QQuoted a ^ "\""
-  | B t -> "$(" ^ to_string t ^ ")"
-
+  | B t ->
+      let s = to_string t in
+      if String.length s >= 2 && s.[0] = '(' && s.[String.length s - 1] = ')' then
+        "$( " ^ s ^ " )"
+      else
+        "$(" ^ s ^ ")"
 and string_of_arg ?quote_mode:(quote_mode=QUnquoted) = function
   | [] -> ""
   | c :: a ->

test/tests/nested_shell_in_subshell.sh

@@ -0,0 +1,4 @@
+( (echo abc) )
+echo $( (echo abc) )
+echo `(echo abc)`
+echo $()