Bug: infix operator dropped

[hhugo]

when using ocp-indent-compat = true
I see the following invalid rewriting.

taken from ocsigen-start.6.1.0:tools/sort_deps.ml

let add_edge target dep =
  if target <> dep
  then (
    Hashtbl.replace edges dep
-      (target :: (try Hashtbl.find edges dep with Not_found -> []));
+      (target (try Hashtbl.find edges dep with Not_found -> []));
    Hashtbl.replace edge_count target
-      (1 + try Hashtbl.find edge_count target with Not_found -> 0);
+      (1 try Hashtbl.find edge_count target with Not_found -> 0);
    if not (Hashtbl.mem edge_count dep) then Hashtbl.add edge_count dep 0)

[gpetiot]

I couldn't fix it but the issue is located in https://github.com/ocaml-ppx/ocamlformat/blob/main/lib/Fmt_ast.ml#L1615-L1623

The way the breaks are added is very flimsy

[hhugo]

The following diff seems to fix the issue.

diff --git a/lib/Fmt_ast.ml b/lib/Fmt_ast.ml
index 36d43f5d..d544d3de 100644
--- a/lib/Fmt_ast.ml
+++ b/lib/Fmt_ast.ml
@@ -2361,6 +2361,7 @@ and fmt_expression c ?(box = true) ?pro ?epi ?eol ?parens ?(indent_wrap = 0)
         if c.conf.fmt_opts.leading_nested_match_parens.v then (false, None)
         else (parenze_exp xpc_rhs, Some false)
       in
+      fmt_opt epi $
       Params.Exp.wrap c.conf ~parens ~disambiguate:true
         (hvbox 2
            ( hvbox 0

[Julow]

Indeed. I went into the rabbit hole of fixing ~pro, ~epi and ~box in fmt_expression in every cases but never got out: https://github.com/Julow/ocamlformat/tree/ocp-indent-op-removed

We might want to use ~pro instead of ~epi and remove the later, as its use doesn't correspond to its name and is used in very few cases.