Print Ppat_constraint

[mununki]

I'd like to print this AST, the intended output is below.

(* AST *)
Pat.record lid
Pat.constraint_
  (Pat.var lid)
  (Typ.constr ~attrs:optionalAttr
      {
        txt = lid;
        loc = Location.none;
      }
      []) )

(* original code in OCaml as intended*)
name: name [@optional]

But the printer generates the output

name: (name: @optional name)

I think this branch needs to be fixed with additional pattern matching for Ppat_constraint.

syntax/src/res_printer.ml

Line 2348 in 6027c1d

| longident, pattern ->

I'm not sure whether it is correct or error.

[cristianoc]

Can you give the repro in source syntax instead of AST?

[mununki]

Sure.

(lid, pattern) https://github.com/mattdamon108/syntax/blob/e207148c945beecf25cf2710dbbc91ee390ed3ff/cli/reactjs_jsx_ppx_v4.ml#L990

which is going to be an arguments of Pat.record at here. https://github.com/mattdamon108/syntax/blob/e207148c945beecf25cf2710dbbc91ee390ed3ff/cli/reactjs_jsx_ppx_v4.ml#L1020

[cristianoc]

Have you tried after this? #584
I assume the issue is still there, but this change touches exactly that area of code.

I'd need a little test snippet in ReScript syntax that gets reprinted to what you've shown.

[cristianoc]

(* original code in OCaml as intended*)
name: name [@optional]

To generate that , you don't want a constraint, you want a Ppat_var with the same name as the label.
Constraint is instead used for type constraints.

[mununki]

(* original code in OCaml as intended*)
name: name [@optional]

To generate that , you don't want a constraint, you want a Ppat_var with the same name as the label. Constraint is instead used for type constraints.

Ouch, you are correct. Thanks!

[cristianoc]

After this #588, assuming all goes well, the change required will be simply to use @ns.optional instead of @optional which will be removed.

[mununki]

Got it, thanks!

[mununki]

Is @ns.optional working same in compiler if I sync the master of submodule syntax? I'm making the binding for React under Js.* There is type domProps = { ... } which is having many fields to have the optional attribute.

[cristianoc]

Is @ns.optional working same in compiler if I sync the master of submodule syntax? I'm making the binding for React under Js.* There is type domProps = { ... } which is having many fields to have the optional attribute.

Not ready yet, but nearly.