Start extracting keywords in foreach command

corpus/foreach_empty.txt

@@ -11,7 +11,7 @@ endforeach()
  (foreach_loop
   (foreach_command
     (foreach)
-    (arguments (argument (unquoted_argument)))
+    (argument (unquoted_argument))
   )
   (endforeach_command (endforeach))
  )
@@ -30,7 +30,7 @@ endforeach(var)
  (foreach_loop
   (foreach_command
     (foreach)
-    (arguments (argument (unquoted_argument)))
+    (argument (unquoted_argument))
   )
   (endforeach_command
     (endforeach)
@@ -51,7 +51,7 @@ ENDFOREACH()
  (foreach_loop
   (foreach_command
     (foreach)
-    (arguments (argument (unquoted_argument)))
+    (argument (unquoted_argument))
   )
   (endforeach_command (endforeach))
  )
@@ -70,7 +70,7 @@ endForEach()
  (foreach_loop
   (foreach_command
     (foreach)
-    (arguments (argument (unquoted_argument)))
+    (argument (unquoted_argument))
   )
   (endforeach_command (endforeach))
  )

grammar.js

@@ -36,10 +36,9 @@ module.exports = grammar({
 
     unquoted_argument: ($) => repeat1(choice($.variable_ref, /[^ ()#\"\\]/, $.escape_sequence)),
 
-    arguments: ($) => seq($.argument, repeat($._seperated_arguments)),
-    _seperated_arguments: ($) => prec.left(seq(repeat1($._seperation), optional($.argument))),
+    arguments: ($) => args($, $.argument),
 
-    foreach_command: ($) => seq($.foreach, "(", $.arguments, ")"),
+    foreach_command: ($) => seq($.foreach, "(", args($, $.argument, "IN"), ")"),
     endforeach_command: ($) =>
       seq($.endforeach, "(", repeat($._seperation), optional($.argument), ")"),
     foreach_loop: ($) =>
@@ -64,3 +63,7 @@ function commandName(name) {
 function commands(...names) {
   return Object.assign({}, ...names.map(commandName));
 }
+
+function args($, ...rules) {
+  return seq(choice(...rules), repeat(prec.left(seq(repeat1($._seperation), optional(choice(...rules))))));
+}

src/grammar.json

@@ -348,21 +348,19 @@
     },
     "arguments": {
       "type": "SEQ",
+      "members": [
+        {
+          "type": "CHOICE",
           "members": [
             {
               "type": "SYMBOL",
               "name": "argument"
+            }
+          ]
         },
         {
           "type": "REPEAT",
           "content": {
-            "type": "SYMBOL",
-            "name": "_seperated_arguments"
-          }
-        }
-      ]
-    },
-    "_seperated_arguments": {
             "type": "PREC_LEFT",
             "value": 0,
             "content": {
@@ -375,12 +373,17 @@
                     "name": "_seperation"
                   }
                 },
+                {
+                  "type": "CHOICE",
+                  "members": [
                     {
                       "type": "CHOICE",
                       "members": [
                         {
                           "type": "SYMBOL",
                           "name": "argument"
+                        }
+                      ]
                     },
                     {
                       "type": "BLANK"
@@ -389,6 +392,9 @@
                 }
               ]
             }
+          }
+        }
+      ]
     },
     "foreach_command": {
       "type": "SEQ",
@@ -401,9 +407,63 @@
           "type": "STRING",
           "value": "("
         },
+        {
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "CHOICE",
+              "members": [
                 {
                   "type": "SYMBOL",
-          "name": "arguments"
+                  "name": "argument"
+                },
+                {
+                  "type": "STRING",
+                  "value": "IN"
+                }
+              ]
+            },
+            {
+              "type": "REPEAT",
+              "content": {
+                "type": "PREC_LEFT",
+                "value": 0,
+                "content": {
+                  "type": "SEQ",
+                  "members": [
+                    {
+                      "type": "REPEAT1",
+                      "content": {
+                        "type": "SYMBOL",
+                        "name": "_seperation"
+                      }
+                    },
+                    {
+                      "type": "CHOICE",
+                      "members": [
+                        {
+                          "type": "CHOICE",
+                          "members": [
+                            {
+                              "type": "SYMBOL",
+                              "name": "argument"
+                            },
+                            {
+                              "type": "STRING",
+                              "value": "IN"
+                            }
+                          ]
+                        },
+                        {
+                          "type": "BLANK"
+                        }
+                      ]
+                    }
+                  ]
+                }
+              }
+            }
+          ]
         },
         {
           "type": "STRING",

src/node-types.json

@@ -120,7 +120,7 @@
       "required": true,
       "types": [
         {
-          "type": "arguments",
+          "type": "argument",
           "named": true
         },
         {
@@ -329,6 +329,10 @@
     "type": "=",
     "named": false
   },
+  {
+    "type": "IN",
+    "named": false
+  },
   {
     "type": "[",
     "named": false