From 7ee866b2aa886e80b74030a174f4c0462a78accb Mon Sep 17 00:00:00 2001
From: Aaron Patterson <tenderlove@ruby-lang.org>
Date: Tue, 21 Mar 2023 13:36:43 -0700
Subject: [PATCH] Add Oxford Comma support

Ruby has regular commas:

```ruby
[a, b, c]
```

Ruby has trailing commas:
```ruby
[
 a,
 b,
 c,
]
```

But I think both of these are hard to read compared to the Oxford comma.
We should introduce the Oxford comma so that code is easier to read:

For example:

```ruby
def foo a, b, and c
  [a, b, and c]
end

p foo(1, 2, and 3)
```

As an added bonus, this feature also makes specifying musical beats
quite natural, for example:

```
[1, and 2, and 3, and 4]
```

Just to make sure that everyone is pleased, you are allowed to mix the
Oxford comma with trailing commas like this:

```
[
  1,
  and 2,
  and 3,
  and 4,
]
```
---
 parse.y | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/parse.y b/parse.y
index 4ef5b88407..090006520c 100644
--- a/parse.y
+++ b/parse.y
@@ -3149,6 +3149,13 @@ args		: arg_value
                     /*% %*/
                     /*% ripper: args_add!($1, $3) %*/
                     }
+                | args ',' keyword_and arg_value
+                    {
+                    /*%%%*/
+                        $$ = last_arg_append(p, $1, $4, &@$);
+                    /*% %*/
+                    /*% ripper: args_add!($1, $4) %*/
+                    }
                 | args ',' tSTAR arg_value
                     {
                     /*%%%*/
@@ -5693,6 +5700,16 @@ f_arg		: f_arg_item
                     /*% %*/
                     /*% ripper: rb_ary_push($1, get_value($3)) %*/
                     }
+                | f_arg ',' keyword_and f_arg_item
+                    {
+                    /*%%%*/
+                        $$ = $1;
+                        $$->nd_plen++;
+                        $$->nd_next = block_append(p, $$->nd_next, $4->nd_next);
+                        rb_discard_node(p, $4);
+                    /*% %*/
+                    /*% ripper: rb_ary_push($1, get_value($4)) %*/
+                    }
                 ;
 
 
-- 
2.37.1