From f804be17e80f7c4014332331f56ed02303185cfb Mon Sep 17 00:00:00 2001
From: Hugo Heuzard <hugo.heuzard@gmail.com>
Date: Thu, 18 Jun 2020 12:16:19 +0100
Subject: [PATCH] Compiler: more conditional compilation based on Environement
 variable

---
 compiler/lib/ocaml_compiler.ml    | 20 ++++++--------------
 compiler/ppx/ppx_optcomp_light.ml | 27 +++++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/compiler/lib/ocaml_compiler.ml b/compiler/lib/ocaml_compiler.ml
index a0463b231f..e51467f94f 100644
--- a/compiler/lib/ocaml_compiler.ml
+++ b/compiler/lib/ocaml_compiler.ml
@@ -35,20 +35,12 @@ let rec constant_of_const : _ -> Code.constant =
   | Const_float_array sl ->
       let l = List.map ~f:(fun f -> Code.Float (float_of_string f)) sl in
       Tuple (Obj.double_array_tag, Array.of_list l, Unknown)
-  (*
-     For bucklescript,
-     - uncomment the two branches below
-     - and comment out the two last ones
-     {[
-       | Const_pointer (i,_) ->
-         Int (Int32.of_int i)
-       | Const_block (tag,_,l) ->
-         let l = Array.of_list (List.map l ~f:constant_of_const) in
-         Tuple (tag, l, Unknown)
-     ]}
-  *)
-  | Const_pointer i -> Int (Int32.of_int i)
-  | Const_block (tag, l) ->
+  | ((Const_pointer (i, _))[@if BUCKLESCRIPT]) -> Int (Int32.of_int i)
+  | ((Const_block (tag, _, l))[@if BUCKLESCRIPT]) ->
+      let l = Array.of_list (List.map l ~f:constant_of_const) in
+      Tuple (tag, l, Unknown)
+  | ((Const_pointer i)[@ifnot BUCKLESCRIPT]) -> Int (Int32.of_int i)
+  | ((Const_block (tag, l))[@ifnot BUCKLESCRIPT]) ->
       let l = Array.of_list (List.map l ~f:constant_of_const) in
       Tuple (tag, l, Unknown)
 
diff --git a/compiler/ppx/ppx_optcomp_light.ml b/compiler/ppx/ppx_optcomp_light.ml
index 5f0d4848de..1433d9cc5b 100644
--- a/compiler/ppx/ppx_optcomp_light.ml
+++ b/compiler/ppx/ppx_optcomp_light.ml
@@ -81,8 +81,31 @@ let keep loc (attrs : attributes) =
   try
     let keep =
       List.for_all attrs ~f:(function
-          | { Location.txt = "if"; _ }, attr_payload -> (
+          | { Location.txt = ("if" | "ifnot") as ifnot; _ }, attr_payload -> (
+              let norm =
+                match ifnot with
+                | "if" -> fun x -> x
+                | "ifnot" -> fun x -> not x
+                | _ -> assert false
+              in
               match attr_payload with
+              | PStr
+                  [ { pstr_desc =
+                        Pstr_eval
+                          ( { pexp_desc = Pexp_construct ({ txt = Lident ident; _ }, None)
+                            ; _
+                            }
+                          , [] )
+                    ; _
+                    }
+                  ] ->
+                  let b =
+                    match bool_of_string (Sys.getenv ident) with
+                    | true -> true
+                    | false -> false
+                    | exception _ -> false
+                  in
+                  norm b
               | PStr
                   [ { pstr_desc =
                         Pstr_eval
@@ -123,7 +146,7 @@ let keep loc (attrs : attributes) =
                   let op = get_op op in
                   let a = eval a in
                   let b = eval b in
-                  op (Version.compare a b) 0
+                  norm (op (Version.compare a b) 0)
               | _ -> raise Invalid)
           | _ -> true)
     in