From 1b38ed43c902805656b01c71495243839724e410 Mon Sep 17 00:00:00 2001
From: Antonio Nuno Monteiro <anmonteiro@gmail.com>
Date: Sat, 27 Jul 2024 21:57:31 -0700
Subject: [PATCH] feat: open any module expr (#2773)

* feat: open any module expr

* changelog, fix printing of pstr_open

* fix
---
 CHANGES.md                             |  5 +++++
 src/reason-parser/reason_parser.mly    |  5 ++---
 src/reason-parser/reason_pprint_ast.ml | 16 ++++++++--------
 test/modules.t/input.re                | 20 ++++++++++++++++++++
 test/modules.t/run.t                   | 20 ++++++++++++++++++++
 5 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index f2dfd5704..6c4fd416c 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,8 @@
+## Unreleased
+
+- Extend open to arbitrary module expression (@anmonteiro,
+  [#2773](https://github.com/reasonml/reason/pull/2773))
+
 ## 3.12.0
 
 - Add `\u{hex-escape}` syntax (@anmonteiro,
diff --git a/src/reason-parser/reason_parser.mly b/src/reason-parser/reason_parser.mly
index e9d04d25f..8603b45fa 100644
--- a/src/reason-parser/reason_parser.mly
+++ b/src/reason-parser/reason_parser.mly
@@ -2566,10 +2566,9 @@ seq_expr_no_seq [@recover.expr default_expr ()] (semi):
    | Some (ext_attrs, ext_id) ->
      mkexp ~loc (Pexp_extension (ext_id, PStr [mkstrexp exp ext_attrs]))
   }
-| item_attributes LET? OPEN override_flag as_loc(mod_longident) SEMI seq_expr(SEMI?)
+| item_attributes LET? OPEN override_flag module_expr SEMI seq_expr(SEMI?)
   { let loc = (mklocation $startpos($1) $endpos($4)) in
-    let me = Ast_helper.Mod.ident ~loc $5 in
-    let od = Ast_helper.Opn.mk ~override:$4 ~loc me in
+    let od = Ast_helper.Opn.mk ~override:$4 ~loc $5 in
     let exp = mkexp (Pexp_open(od, $7)) in
     { exp with pexp_attributes = $1 }
   }
diff --git a/src/reason-parser/reason_pprint_ast.ml b/src/reason-parser/reason_pprint_ast.ml
index 31144c30b..35bc91f45 100644
--- a/src/reason-parser/reason_pprint_ast.ml
+++ b/src/reason-parser/reason_pprint_ast.ml
@@ -162,7 +162,7 @@ let expression_immediate_extension_sugar x =
   | Some (name, expr) ->
     match expr.pexp_desc with
     | Pexp_for _ | Pexp_while _ | Pexp_ifthenelse _ | Pexp_function _
-    | Pexp_newtype _ | Pexp_try _ | Pexp_match _ (* | Pexp_letmodule _ *) ->
+    | Pexp_newtype _ | Pexp_try _ | Pexp_match _ ->
       (Some name, expr)
     | _ -> (None, x)
 
@@ -6236,8 +6236,9 @@ let printer = object(self:'self)
         | ([], Pexp_letop _) -> false
         | ([], Pexp_sequence _) -> false
         | ([], Pexp_letmodule _) -> false
-        | ([], Pexp_open (me, e)) ->
-          me.popen_override == Fresh && self#isSeriesOfOpensFollowedByNonSequencyExpression e
+        | ([], Pexp_open ({ popen_override; popen_expr = { pmod_desc = Pmod_ident _; _ }; _ }, e)) ->
+          popen_override == Fresh && self#isSeriesOfOpensFollowedByNonSequencyExpression e
+        | ([], Pexp_open _) -> false
         | ([], Pexp_letexception _) -> false
         | ([], Pexp_extension ({txt}, _)) -> txt = "mel.obj"
         | _ -> true
@@ -6478,7 +6479,7 @@ let printer = object(self:'self)
                     (atom (".")))
                   (self#formatNonSequencyExpression ~parent:x e))
             else
-              Some  (makeLetSequence (self#letList e))
+              Some (makeLetSequence (self#letList x))
         | Pexp_send (e, s) ->
           let needparens = match e.pexp_desc with
             | Pexp_apply (ee, _) ->
@@ -7812,10 +7813,9 @@ let printer = object(self:'self)
             self#attach_std_item_attrs binding.pmb_attributes module_binding
         | Pstr_open od ->
             self#attach_std_item_attrs od.popen_attributes @@
-            makeList ~postSpace:true [
-              atom ("open" ^ (override od.popen_override));
-              self#moduleExpressionToFormattedApplicationItems od.popen_expr;
-            ]
+            label ~space:true
+              (atom ("open" ^ (override od.popen_override)))
+              (self#moduleExpressionToFormattedApplicationItems od.popen_expr)
         | Pstr_modtype x ->
             let name = atom x.pmtd_name.txt in
             let letPattern = makeList ~postSpace:true [atom "module type"; name; atom "="] in
diff --git a/test/modules.t/input.re b/test/modules.t/input.re
index 9846a7660..3e7e4314b 100644
--- a/test/modules.t/input.re
+++ b/test/modules.t/input.re
@@ -540,3 +540,23 @@ let x = {
 module%foo rec X: Y = {
   let x = 1;
 }
+
+let f = () => {
+  open {
+    let x = 1;
+  };
+  ();
+};
+
+let f = () => {
+  let open {
+    let x = 1;
+  };
+  ();
+};
+
+open {
+  let x = 1;
+};
+
+
diff --git a/test/modules.t/run.t b/test/modules.t/run.t
index dc3fe3913..7c2d5cc62 100644
--- a/test/modules.t/run.t
+++ b/test/modules.t/run.t
@@ -706,4 +706,24 @@ Format modules
   module%foo rec X: Y = {
     let x = 1;
   };
+  
+  let f = () => {
+    open {
+      let x = 1;
+    };
+  
+    ();
+  };
+  
+  let f = () => {
+    open {
+      let x = 1;
+    };
+  
+    ();
+  };
+  
+  open {
+    let x = 1;
+  };
 /* From http://stackoverflow.com/questions/1986374/  higher-order-type-constructors-and-functors-in-ocaml */