From 2b6d9126c1b92ad24bedc80ac28a1d3fe189fc6a Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Tue, 5 Nov 2019 19:02:16 -0600
Subject: [PATCH] feat(ccsexp): support `#;` for commenting a sexp

---
 src/sexp/CCSexp.ml      | 15 ++++++++++++++-
 src/sexp/CCSexp_lex.mll |  2 ++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/sexp/CCSexp.ml b/src/sexp/CCSexp.ml
index 7c4a8471..c5486528 100644
--- a/src/sexp/CCSexp.ml
+++ b/src/sexp/CCSexp.ml
@@ -195,6 +195,10 @@ module Decoder = struct
   let next (t:t) =
     let rec expr () = match cur t with
       | L.EOI -> raise E_end
+      | L.SEXP_COMMENT ->
+        junk t;
+        let _u = expr() in (* discard next sexp *)
+        expr()
       | L.ATOM s -> junk t; `Atom s
       | L.LIST_OPEN ->
         junk t;
@@ -206,7 +210,7 @@ module Decoder = struct
       | L.LIST_CLOSE -> error_ t.buf "expected expression"
     and lst acc = match cur t with
       | L.LIST_CLOSE -> List.rev acc
-      | L.LIST_OPEN | L.ATOM _ ->
+      | L.LIST_OPEN | L.ATOM _ | L.SEXP_COMMENT ->
         let sub = expr () in
         lst (sub::acc)
       | L.EOI -> error_ t.buf "unexpected EOI"
@@ -233,6 +237,15 @@ let parse_string s : t or_error =
   CCResult.to_opt (parse_string "\"\123\bcoucou\"") <> None
 *)
 
+(*$= & ~printer:(function Ok x -> to_string x | Error e -> "error " ^ e)
+  (parse_string "(a b)") (Ok (`List [`Atom "a"; `Atom "b"]))
+  (parse_string "(a\n ;coucou\n b)") (Ok (`List [`Atom "a"; `Atom "b"]))
+  (parse_string "(a #; (foo bar\n (1 2 3)) b)") (Ok (`List [`Atom "a"; `Atom "b"]))
+  (parse_string "#; (a b) (c d)") (Ok (`List [`Atom "c"; `Atom "d"]))
+  (parse_string "#; (a b) 1") (Ok (`Atom "1"))
+*)
+
+
 (*$inject
   let sexp_gen =
     let mkatom a = `Atom a and mklist l = `List l in
diff --git a/src/sexp/CCSexp_lex.mll b/src/sexp/CCSexp_lex.mll
index 3db73cd6..f8216a4b 100644
--- a/src/sexp/CCSexp_lex.mll
+++ b/src/sexp/CCSexp_lex.mll
@@ -4,6 +4,7 @@
     | ATOM of string
     | LIST_OPEN
     | LIST_CLOSE
+    | SEXP_COMMENT
     | EOI
 
   (* location + message *)
@@ -65,6 +66,7 @@ let string_item =
 let string = '"' string_item* '"'
 
 rule token = parse
+  | "#;" { SEXP_COMMENT }
   | comment_line { token lexbuf }
   | newline { Lexing.new_line lexbuf; token lexbuf }
   | white { token lexbuf }