Make $.variable recursive

corpus/quoted_argument.txt

@@ -96,3 +96,23 @@ message("${var} ${var}")
   )
  )
  )
+
+======================================================================
+Variable reference inside another variable reference [quoted_argument]
+======================================================================
+
+message("${var_${var}}")
+
+---
+(source_file
+ (normal_command
+  (identifier)
+  (argument
+   (quoted_argument
+    (quoted_element
+     (variable_ref (normal_var (variable (variable_ref (normal_var (variable))))))
+    )
+   )
+  )
+ )
+ )

corpus/unquoted_argument.txt

@@ -85,3 +85,20 @@ message(${var_ref})
  )
  )
 
+====================================================================
+Variable referencing inside variable referencing [unquoted_argument]
+====================================================================
+message(${var_${var_ref}})
+---
+
+(source_file
+ (normal_command
+  (identifier)
+  (argument
+   (unquoted_argument
+    (variable_ref (normal_var (variable (variable_ref (normal_var (variable))))))
+   )
+  )
+ )
+ )
+

grammar.js

@@ -27,7 +27,7 @@ module.exports = grammar({
     _escape_encoded: (_) => choice("\\t", "\\r", "\\n"),
     _escape_semicolon: (_) => ";",
 
-    variable: ($) => prec.left(repeat1(choice(/[a-zA-Z0-9/_.+-]/, $.escape_sequence))),
+    variable: ($) => prec.left(repeat1(choice(/[a-zA-Z0-9/_.+-]/, $.escape_sequence, $.variable_ref))),
     variable_ref: ($) => choice($.normal_var, $.env_var, $.cache_var),
     normal_var: ($) => seq("${", $.variable, "}"),
     env_var: ($) => seq("$ENV", "{", $.variable, "}"),

src/grammar.json

@@ -65,6 +65,10 @@
             {
               "type": "SYMBOL",
               "name": "escape_sequence"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "variable_ref"
             }
           ]
         }

src/node-types.json

@@ -579,6 +579,10 @@
         {
           "type": "escape_sequence",
           "named": true
+        },
+        {
+          "type": "variable_ref",
+          "named": true
         }
       ]
     }