Unexpected formatting while saving an ocamllex file

[francoisthire]

Using extension v1.18.1 with OCaml version 5.2.0 (and 4.14.2), I have an unexpected behaviour when saving an ocamllex file (ending in .mll). The extension formats the file in a way which is no longer valid but also not readable.

My example is the following one:

{
  open Parser

  exception Error of string

  let fail explanation = raise (Error explanation)
}

let space = [' ' '\t' '\r']+

let ident = ['a'-'z''A'-'Z''0'-'9''_']+


rule token =
  parse
  | space        { token lexbuf }
  | '\n'         { Lexing.new_line lexbuf; token lexbuf }
  | "Type"       { TYPE }  
  | ':'          { COLON }
  | '.'          { DOT }
  | eof          { EOF }
  | ident as id  { ID id }  
  | _ as c { fail (Printf.sprintf "Unexpected character: %C (codepoint: %d)" c (Char.code c)) }

and on save, the extension produces this file:

{

open

Parser

exception

Error

of

string

let

fail

explanation

=

raise

(Error explanation)

}

let

space

=

['

'

'\t'

'\r']+

let

ident

=

['a'-'z''A'-'Z''0'-'9''_']+

rule

token

=

parse

|

space

{

token

lexbuf

}

|

'\n'

{

Lexing.new_line

lexbuf

; token lexbuf }

|

"Type"

{

TYPE

}

|

':'

{

COLON

}

|

'.'

{

DOT

}

|

eof

{

EOF

}

|

ident

as

id

{

ID

id

}

|

_

as

c

{

fail

(Printf.sprintf
 "Unexpected character: %C (codepoint: %d)"
 c
 (Char.code c))

}

Deactivating the extension enables to not observe this behaviour.

[Kakadu]

I think that disabling ocamlformat for these kind of files is only approach. Good luck!