ocaml-sys / config.ml Goto Github PK

Right now we can't use @cfg in elements defined within modules and signatures.

The expected behavior is that @cfg can be used in places like this:

module A : sig
 val a : unit -> unit [@@cfg disable = true]
end =
 let a () = () [@@cfg disable = true]
end

and interface files:

module A : sig
 val a : unit -> unit [@@cfg disable = true]
end

Currently, this is unsupported:

let foo a =
  match a with
  | 0 -> "0"
  | 1 -> "1"
  [@@cfg (disable=true)]

And the expected behavior is that we can remove that match case with the annotation.

This is mostly important for having good support for conditional constructors and variants, so that we can disable in tandem the pattern matching branches for them.

Context: In DkCoder https://discuss.ocaml.org/t/ann-dkcoder-0-1-0/14327 I'm exposing OS/ABI from https://github.com/diskuv/dkml-c-probe as environment variables to scripts, and I've been planning on exposing a cfg mechanism.

For a lot of reasons ¹ I'll have to fork but thought I would ask regardless. Is there something about config that needs OCaml 5.1+?

¹ OCaml 5 / dkml-c-probe / whitelist control over envvars / restriction to modules for integration with codept / ...

Currently, this is unsupported:

let foo a = function
  | 0 -> "0"
  | 1 -> "1"
  [@@cfg (disable=true)]

And the expected behavior is that we can remove that function branch with the annotation.

It looks like annotating [@config (not(a = 1))] actually breaks at evaluation time with:

   $ dune clean
   $ dune build
+  File "cond_type_var_constructor.ml", line 16, characters 17-48:
+  16 |   | `KingCrimson [@config (not(made_up = true))]
+                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  Error: Not expressions must have a single parameter
+         
+  [1]

And using a variable to test for it being unset like [@config (not(a))], failed with:

   $ dune clean
   $ dune build
+  File "cond_type_var_constructor.ml", line 16, characters 17-41:
+  16 |   | `KingCrimson [@config (not(made_up))]
+                        ^^^^^^^^^^^^^^^^^^^^^^^^
+  Error: Forms any/all/not must parenthesize its arguments
+         
+  [1]

The expected behavior is that both of these parse correctly and evaluate as follows:

• not(expr) is equals to false if the expression is true, or true if it is false
• not(varName) is equals to true if the varName is not defined in the environment or has no value, or false if varName has a value