From 75baecdb6cd567b7cf5d34f4d6d294e4d9b1feaa Mon Sep 17 00:00:00 2001
From: EmileTrotignon <emile.trotignon@gmail.com>
Date: Fri, 6 Jun 2025 18:58:09 +0200
Subject: [PATCH 1/2] makes exp-grouping=preserve the default

---
 lib/Conf.ml                                   |  12 +-
 test/cli/print_config.t                       |   6 +-
 test/passing/refs.default/effects.ml.ref      |   8 +-
 test/passing/refs.default/ifand.ml.ref        |   4 +-
 test/passing/refs.default/js_begin.ml.ref     |   7 +-
 test/passing/refs.default/js_pattern.ml.ref   |   5 +-
 .../refs.default/reformat_string.ml.ref       |  13 +-
 .../refs.default/sequence-preserve.ml.ref     |   8 +-
 test/passing/refs.default/sequence.ml.ref     |   8 +-
 test/passing/refs.default/source.ml.err       |   4 +-
 test/passing/refs.default/source.ml.ref       | 129 +++++++++------
 test/passing/refs.ocamlformat/effects.ml.ref  |   8 +-
 test/passing/refs.ocamlformat/ifand.ml.ref    |   5 +-
 test/passing/refs.ocamlformat/js_begin.ml.ref |   6 +-
 .../refs.ocamlformat/js_pattern.ml.ref        |   4 +-
 .../refs.ocamlformat/reformat_string.ml.ref   |  12 +-
 .../refs.ocamlformat/sequence-preserve.ml.ref |   8 +-
 test/passing/refs.ocamlformat/sequence.ml.ref |   8 +-
 test/passing/refs.ocamlformat/source.ml.err   |   6 +-
 test/passing/refs.ocamlformat/source.ml.ref   | 152 ++++++++++--------
 test/unit/test_fmt_ast.ml                     |   2 +-
 21 files changed, 255 insertions(+), 160 deletions(-)

diff --git a/lib/Conf.ml b/lib/Conf.ml
index c1ab15d13f..def15f781d 100644
--- a/lib/Conf.ml
+++ b/lib/Conf.ml
@@ -70,7 +70,7 @@ let conventional_profile from =
   ; doc_comments_padding= elt 2
   ; doc_comments_tag_only= elt `Default
   ; dock_collection_brackets= elt true
-  ; exp_grouping= elt `Parens
+  ; exp_grouping= elt `Preserve
   ; extension_indent= elt 2
   ; field_space= elt `Loose
   ; function_indent= elt 2
@@ -139,7 +139,7 @@ let ocamlformat_profile from =
   ; doc_comments_padding= elt 2
   ; doc_comments_tag_only= elt `Default
   ; dock_collection_brackets= elt false
-  ; exp_grouping= elt `Parens
+  ; exp_grouping= elt `Preserve
   ; extension_indent= elt 2
   ; field_space= elt `Tight
   ; function_indent= elt 2
@@ -742,11 +742,11 @@ module Formatting = struct
     let doc = "Style of expression grouping." in
     let names = ["exp-grouping"] in
     let all =
-      [ Decl.Value.make ~name:"parens" `Parens
-          "$(b,parens) groups expressions using parentheses."
-      ; Decl.Value.make ~name:"preserve" `Preserve
+      [ Decl.Value.make ~name:"preserve" `Preserve
           "$(b,preserve) preserves the original grouping syntax \
-           (parentheses or $(i,begin)/$(i,end))." ]
+           (parentheses or $(i,begin)/$(i,end))."
+      ; Decl.Value.make ~name:"parens" `Parens
+          "$(b,parens) groups expressions using parentheses." ]
     in
     Decl.choice ~names ~all ~default ~doc ~kind ~allow_inline:false
       (fun conf elt -> update conf ~f:(fun f -> {f with exp_grouping= elt}))
diff --git a/test/cli/print_config.t b/test/cli/print_config.t
index 1f608ef9d9..def057d484 100644
--- a/test/cli/print_config.t
+++ b/test/cli/print_config.t
@@ -42,7 +42,7 @@ No redundant values:
   doc-comments-padding=2 (profile conventional (file .ocamlformat:1))
   doc-comments-tag-only=default (profile conventional (file .ocamlformat:1))
   dock-collection-brackets=true (profile conventional (file .ocamlformat:1))
-  exp-grouping=parens (profile conventional (file .ocamlformat:1))
+  exp-grouping=preserve (profile conventional (file .ocamlformat:1))
   extension-indent=2 (profile conventional (file .ocamlformat:1))
   field-space=tight (file .ocamlformat:2)
   function-indent=2 (profile conventional (file .ocamlformat:1))
@@ -121,7 +121,7 @@ Redundant values from the conventional profile:
   doc-comments-padding=2 (profile conventional (file .ocamlformat:1))
   doc-comments-tag-only=default (profile conventional (file .ocamlformat:1))
   dock-collection-brackets=true (profile conventional (file .ocamlformat:1))
-  exp-grouping=parens (profile conventional (file .ocamlformat:1))
+  exp-grouping=preserve (profile conventional (file .ocamlformat:1))
   extension-indent=2 (profile conventional (file .ocamlformat:1))
   field-space=loose (profile conventional (file .ocamlformat:1))
   function-indent=2 (profile conventional (file .ocamlformat:1))
@@ -200,7 +200,7 @@ Redundant values from the ocamlformat profile:
   doc-comments-padding=2 (profile ocamlformat (file .ocamlformat:1))
   doc-comments-tag-only=default (profile ocamlformat (file .ocamlformat:1))
   dock-collection-brackets=false (profile ocamlformat (file .ocamlformat:1))
-  exp-grouping=parens (profile ocamlformat (file .ocamlformat:1))
+  exp-grouping=preserve (profile ocamlformat (file .ocamlformat:1))
   extension-indent=2 (profile ocamlformat (file .ocamlformat:1))
   field-space=tight (profile ocamlformat (file .ocamlformat:1))
   function-indent=2 (profile ocamlformat (file .ocamlformat:1))
diff --git a/test/passing/refs.default/effects.ml.ref b/test/passing/refs.default/effects.ml.ref
index 6754d37966..a4b3fda1ca 100644
--- a/test/passing/refs.default/effects.ml.ref
+++ b/test/passing/refs.default/effects.ml.ref
@@ -16,9 +16,10 @@ let run (main : unit -> unit) : unit =
   in
   let dequeue () =
     if Queue.is_empty run_q then () (* done *)
-    else
+    else begin
       let task = Queue.pop run_q in
       task ()
+    end
   in
   let rec spawn (f : unit -> unit) : unit =
     match f () with
@@ -32,7 +33,7 @@ let run (main : unit -> unit) : unit =
     | effect Fork f, k ->
         enqueue k ();
         spawn f
-    | effect Xchg n, k -> (
+    | effect Xchg n, k -> begin
         match !exchanger with
         | Some (n', k') ->
             exchanger := None;
@@ -40,7 +41,8 @@ let run (main : unit -> unit) : unit =
             continue k n'
         | None ->
             exchanger := Some (n, k);
-            dequeue ())
+            dequeue ()
+      end
   in
   spawn main
 
diff --git a/test/passing/refs.default/ifand.ml.ref b/test/passing/refs.default/ifand.ml.ref
index 1424110fdb..3d1c0c0816 100644
--- a/test/passing/refs.default/ifand.ml.ref
+++ b/test/passing/refs.default/ifand.ml.ref
@@ -1,2 +1,4 @@
 let _ = if cond1 && cond2 then _
-let _ = function _ when x = 2 && y = 3 -> if a = b || (b = c && c = d) then _
+
+let _ = function
+  | _ when x = 2 && y = 3 -> begin if a = b || (b = c && c = d) then _ end
diff --git a/test/passing/refs.default/js_begin.ml.ref b/test/passing/refs.default/js_begin.ml.ref
index 43cb1a7e09..36e2430e79 100644
--- a/test/passing/refs.default/js_begin.ml.ref
+++ b/test/passing/refs.default/js_begin.ml.ref
@@ -1,11 +1,14 @@
 let f = function
-  | zoo ->
+  | zoo -> begin
       foo;
       bar
+    end
 
 let g = function
   | zoo ->
       foo;
       bar
 
-let () = match foo with Bar -> snoo
+let () =
+  begin match foo with Bar -> snoo
+  end
diff --git a/test/passing/refs.default/js_pattern.ml.ref b/test/passing/refs.default/js_pattern.ml.ref
index c59b7c9b06..31b486bc70 100644
--- a/test/passing/refs.default/js_pattern.ml.ref
+++ b/test/passing/refs.default/js_pattern.ml.ref
@@ -2,7 +2,10 @@ let f = function _ -> 0
 let f x = match x with _ -> 0
 let f = function _ -> 0
 let f x = match x with _ -> 0
-let f x = match x with _ -> 0
+
+let f x =
+  begin match x with _ -> 0
+  end
 
 let check_price t = function
   | { Exec.trade_at_settlement = None | Some false } -> ()
diff --git a/test/passing/refs.default/reformat_string.ml.ref b/test/passing/refs.default/reformat_string.ml.ref
index edef79e0e9..8a4c2d022b 100644
--- a/test/passing/refs.default/reformat_string.ml.ref
+++ b/test/passing/refs.default/reformat_string.ml.ref
@@ -2,8 +2,17 @@ let _ = 'a'
 let _ = 'a'
 let _ = (* test *) "asd"
 let _ = "asd"
-let _ = (* te""st *) "asd"
-let _ = "asd"
+
+let _ =
+  begin
+    (* te""st *) "asd"
+  end
+
+let _ =
+  begin
+    "asd"
+  end
+
 let _ = 'a'
 let _ = 'a'
 let _ = function 'a' .. 'z' -> ()
diff --git a/test/passing/refs.default/sequence-preserve.ml.ref b/test/passing/refs.default/sequence-preserve.ml.ref
index 62dcb05c1b..044a555db9 100644
--- a/test/passing/refs.default/sequence-preserve.ml.ref
+++ b/test/passing/refs.default/sequence-preserve.ml.ref
@@ -1,8 +1,10 @@
 let read_traces filename =
   let ic = open_in_bin filename in
-  read_hashtable ~t:[%t: contracts_trace] 0 40 ic tbl1;
-  read_hashtable ~t:[%t: variables_trace] 40 70 ic tbl2;
-  read_hashtable ~t:[%t: expressions_trace] 70 100 ic tbl3;
+  begin
+    read_hashtable ~t:[%t: contracts_trace] 0 40 ic tbl1;
+    read_hashtable ~t:[%t: variables_trace] 40 70 ic tbl2;
+    read_hashtable ~t:[%t: expressions_trace] 70 100 ic tbl3
+  end;
   close_in ic
 
 let foo x y =
diff --git a/test/passing/refs.default/sequence.ml.ref b/test/passing/refs.default/sequence.ml.ref
index b84db9cf51..790e1b9b72 100644
--- a/test/passing/refs.default/sequence.ml.ref
+++ b/test/passing/refs.default/sequence.ml.ref
@@ -1,8 +1,10 @@
 let read_traces filename =
   let ic = open_in_bin filename in
-  read_hashtable ~t:[%t: contracts_trace] 0 40 ic tbl1;
-  read_hashtable ~t:[%t: variables_trace] 40 70 ic tbl2;
-  read_hashtable ~t:[%t: expressions_trace] 70 100 ic tbl3;
+  begin
+    read_hashtable ~t:[%t: contracts_trace] 0 40 ic tbl1;
+    read_hashtable ~t:[%t: variables_trace] 40 70 ic tbl2;
+    read_hashtable ~t:[%t: expressions_trace] 70 100 ic tbl3
+  end;
   close_in ic
 
 let foo x y =
diff --git a/test/passing/refs.default/source.ml.err b/test/passing/refs.default/source.ml.err
index eb0c35513d..70d6121ff4 100644
--- a/test/passing/refs.default/source.ml.err
+++ b/test/passing/refs.default/source.ml.err
@@ -1,4 +1,4 @@
 Warning: source.ml:919 exceeds the margin
 Warning: source.ml:994 exceeds the margin
-Warning: source.ml:6616 exceeds the margin
-Warning: source.ml:7074 exceeds the margin
+Warning: source.ml:6640 exceeds the margin
+Warning: source.ml:7099 exceeds the margin
diff --git a/test/passing/refs.default/source.ml.ref b/test/passing/refs.default/source.ml.ref
index 559d3e27c4..46ac2f09dd 100644
--- a/test/passing/refs.default/source.ml.ref
+++ b/test/passing/refs.default/source.ml.ref
@@ -1096,14 +1096,16 @@ let rec get_case : type a b e.
     =
  fun sel cases ->
   match cases with
-  | (name, TCnoarg sel') :: rem -> (
+  | (name, TCnoarg sel') :: rem -> begin
       match eq_sel sel sel' with
       | None -> get_case sel rem
-      | Some Eq -> (name, None))
-  | (name, TCarg (sel', ty)) :: rem -> (
+      | Some Eq -> (name, None)
+    end
+  | (name, TCarg (sel', ty)) :: rem -> begin
       match eq_sel sel sel' with
       | None -> get_case sel rem
-      | Some Eq -> (name, Some ty))
+      | Some Eq -> (name, Some ty)
+    end
   | [] -> raise Not_found
 
 (* Untyped representation of values *)
@@ -1147,13 +1149,14 @@ let rec devariantize : type t e. e ty_env -> (t, e) ty -> variant -> t =
   | Var, _ -> ( match e with Econs (t, e') -> devariantize e' t v)
   | Conv (s, proj, inj, t), VConv (s', v) when s = s' ->
       inj (devariantize e t v)
-  | Sum ops, VSum (tag, a) -> (
+  | Sum ops, VSum (tag, a) -> begin
       try
         match (List.assoc tag ops.sum_cases, a) with
         | TCarg (sel, t), Some a -> ops.sum_inj (sel, devariantize e t a)
         | TCnoarg sel, None -> ops.sum_inj (sel, Noarg)
         | _ -> raise VariantMismatch
-      with Not_found -> raise VariantMismatch)
+      with Not_found -> raise VariantMismatch
+    end
   | _ -> raise VariantMismatch
 
 (* First attempt: represent 1-constructor variants using Conv *)
@@ -1483,8 +1486,9 @@ let rec sameNat : type a b. a nat -> b nat -> (a, b) equal option =
  fun a b ->
   match (a, b) with
   | NZ, NZ -> Some Eq
-  | NS a', NS b' -> (
-      match sameNat a' b' with Some Eq -> Some Eq | None -> None)
+  | NS a', NS b' -> begin
+      match sameNat a' b' with Some Eq -> Some Eq | None -> None
+    end
   | _ -> None
 
 (* Extra: associativity of addition *)
@@ -1627,9 +1631,9 @@ let rec ins : type n. int -> n avl -> (n avl, n succ avl) sum =
  fun x t ->
   match t with
   | Leaf -> Inr (Node (Same, Leaf, x, Leaf))
-  | Node (bal, a, y, b) -> (
+  | Node (bal, a, y, b) ->
       if x = y then Inl t
-      else if x < y then
+      else if x < y then begin
         match ins x a with
         | Inl a -> Inl (Node (bal, a, y, b))
         | Inr a -> (
@@ -1637,14 +1641,16 @@ let rec ins : type n. int -> n avl -> (n avl, n succ avl) sum =
             | Less -> Inl (Node (Same, a, y, b))
             | Same -> Inr (Node (More, a, y, b))
             | More -> rotr a y b)
-      else
+      end
+      else begin
         match ins x b with
         | Inl b -> Inl (Node (bal, a, y, b) : n avl)
         | Inr b -> (
             match bal with
             | More -> Inl (Node (Same, a, y, b) : n avl)
             | Same -> Inr (Node (Less, a, y, b) : n succ avl)
-            | Less -> rotl a y b))
+            | Less -> rotl a y b)
+      end
 
 let insert x (Avl t) = match ins x t with Inl t -> Avl t | Inr t -> Avl t
 
@@ -1669,12 +1675,13 @@ let rec del : type n. int -> n avl -> n avl_del =
  fun y t ->
   match t with
   | Leaf -> Dsame Leaf
-  | Node (bal, l, x, r) -> (
-      if x = y then
+  | Node (bal, l, x, r) ->
+      if x = y then begin
         match r with
-        | Leaf -> (
-            match bal with Same -> Ddecr (Eq, l) | More -> Ddecr (Eq, l))
-        | Node _ -> (
+        | Leaf -> begin
+            match bal with Same -> Ddecr (Eq, l) | More -> Ddecr (Eq, l)
+          end
+        | Node _ -> begin
             match (bal, del_min r) with
             | _, (z, Inr r) -> Dsame (Node (bal, l, z, r))
             | Same, (z, Inl r) -> Dsame (Node (More, l, z, r))
@@ -1682,29 +1689,35 @@ let rec del : type n. int -> n avl -> n avl_del =
             | More, (z, Inl r) -> (
                 match rotr l z r with
                 | Inl t -> Ddecr (Eq, t)
-                | Inr t -> Dsame t))
-      else if y < x then
+                | Inr t -> Dsame t)
+          end
+      end
+      else if y < x then begin
         match del y l with
         | Dsame l -> Dsame (Node (bal, l, x, r))
-        | Ddecr (Eq, l) -> (
+        | Ddecr (Eq, l) -> begin
             match bal with
             | Same -> Dsame (Node (Less, l, x, r))
             | More -> Ddecr (Eq, Node (Same, l, x, r))
             | Less -> (
                 match rotl l x r with
                 | Inl t -> Ddecr (Eq, t)
-                | Inr t -> Dsame t))
-      else
+                | Inr t -> Dsame t)
+          end
+      end
+      else begin
         match del y r with
         | Dsame r -> Dsame (Node (bal, l, x, r))
-        | Ddecr (Eq, r) -> (
+        | Ddecr (Eq, r) -> begin
             match bal with
             | Same -> Dsame (Node (More, l, x, r))
             | Less -> Ddecr (Eq, Node (Same, l, x, r))
             | More -> (
                 match rotr l x r with
                 | Inl t -> Ddecr (Eq, t)
-                | Inr t -> Dsame t)))
+                | Inr t -> Dsame t)
+          end
+      end
 
 let delete x (Avl t) =
   match del x t with Dsame t -> Avl t | Ddecr (_, t) -> Avl t
@@ -1821,16 +1834,18 @@ let rec rep_equal : type a b. a rep -> b rep -> (a, b) equal option =
   match (ra, rb) with
   | Rint, Rint -> Some Eq
   | Rbool, Rbool -> Some Eq
-  | Rpair (a1, a2), Rpair (b1, b2) -> (
+  | Rpair (a1, a2), Rpair (b1, b2) -> begin
       match rep_equal a1 b1 with
       | None -> None
       | Some Eq -> (
-          match rep_equal a2 b2 with None -> None | Some Eq -> Some Eq))
-  | Rfun (a1, a2), Rfun (b1, b2) -> (
+          match rep_equal a2 b2 with None -> None | Some Eq -> Some Eq)
+    end
+  | Rfun (a1, a2), Rfun (b1, b2) -> begin
       match rep_equal a1 b1 with
       | None -> None
       | Some Eq -> (
-          match rep_equal a2 b2 with None -> None | Some Eq -> Some Eq))
+          match rep_equal a2 b2 with None -> None | Some Eq -> Some Eq)
+    end
   | _ -> None
 
 type assoc = Assoc : string * 'a rep * 'a -> assoc
@@ -1928,10 +1943,11 @@ let rec compare : type a b. a rep -> b rep -> (string, (a, b) equal) sum =
  fun a b ->
   match (a, b) with
   | I, I -> Inr Eq
-  | Ar (x, y), Ar (s, t) -> (
+  | Ar (x, y), Ar (s, t) -> begin
       match compare x s with
       | Inl _ as e -> e
-      | Inr Eq -> ( match compare y t with Inl _ as e -> e | Inr Eq as e -> e))
+      | Inr Eq -> ( match compare y t with Inl _ as e -> e | Inr Eq as e -> e)
+    end
   | I, Ar _ -> Inl "I <> Ar _"
   | Ar _, I -> Inl "Ar _ <> I"
 
@@ -1962,7 +1978,7 @@ let rec tc : type n e. n nat -> e ctx -> term -> e checked =
  fun n ctx t ->
   match t with
   | V s -> lookup s ctx
-  | Ap (f, x) -> (
+  | Ap (f, x) -> begin
       match tc n ctx f with
       | Cerror _ as e -> e
       | Cok (f', ft) -> (
@@ -1970,15 +1986,18 @@ let rec tc : type n e. n nat -> e ctx -> term -> e checked =
           | Cerror _ as e -> e
           | Cok (x', xt) -> (
               match ft with
-              | Ar (a, b) -> (
+              | Ar (a, b) -> begin
                   match compare a xt with
                   | Inl s -> Cerror s
-                  | Inr Eq -> Cok (App (f', x'), b))
-              | _ -> Cerror "Non fun in Ap")))
-  | Ab (s, t, body) -> (
+                  | Inr Eq -> Cok (App (f', x'), b)
+                end
+              | _ -> Cerror "Non fun in Ap"))
+    end
+  | Ab (s, t, body) -> begin
       match tc (NS n) (Ccons (n, s, t, ctx)) body with
       | Cerror _ as e -> e
-      | Cok (body', et) -> Cok (Abs (n, body'), Ar (t, et)))
+      | Cok (body', et) -> Cok (Abs (n, body'), Ar (t, et))
+    end
   | C m -> Cok (Const m, I)
 
 let ctx0 =
@@ -2058,9 +2077,10 @@ let rec rule : type a b.
     (pval, closed, (a, b) tarr) lam -> (pval, closed, a) lam -> b rlam =
  fun v1 v2 ->
   match (v1, v2) with
-  | Lam (x, body), v -> (
+  | Lam (x, body), v -> begin
       match subst body (Bind (x, v, Id)) with
-      | Ex term -> ( match mode term with Pexp -> Inl term | Pval -> Inr term))
+      | Ex term -> ( match mode term with Pexp -> Inl term | Pval -> Inr term)
+    end
   | Const (IntTo b, f), Const (IntR, x) -> Inr (Const (b, f x))
 
 let rec onestep : type m t. (m, closed, t) lam -> t rlam = function
@@ -2068,14 +2088,16 @@ let rec onestep : type m t. (m, closed, t) lam -> t rlam = function
   | Const (r, v) -> Inr (Const (r, v))
   | App (e1, e2) -> (
       match (mode e1, mode e2) with
-      | Pexp, _ -> (
+      | Pexp, _ -> begin
           match onestep e1 with
           | Inl e -> Inl (App (e, e2))
-          | Inr v -> Inl (App (v, e2)))
-      | Pval, Pexp -> (
+          | Inr v -> Inl (App (v, e2))
+        end
+      | Pval, Pexp -> begin
           match onestep e2 with
           | Inl e -> Inl (App (e1, e))
-          | Inr v -> Inl (App (e1, v)))
+          | Inr v -> Inl (App (e1, v))
+        end
       | Pval, Pval -> rule e1 e2)
 
 type ('env, 'a) var =
@@ -5765,10 +5787,12 @@ module UText = struct
 
   let set_buf s i u =
     let n = UChar.uint_code u in
-    s.![i] <- Char.chr (n lsr 24);
-    s.![i + 1] <- Char.chr ((n lsr 16) lor 0xff);
-    s.![i + 2] <- Char.chr ((n lsr 8) lor 0xff);
-    s.![i + 3] <- Char.chr (n lor 0xff)
+    begin
+      s.![i] <- Char.chr (n lsr 24);
+      s.![i + 1] <- Char.chr ((n lsr 16) lor 0xff);
+      s.![i + 2] <- Char.chr ((n lsr 8) lor 0xff);
+      s.![i + 3] <- Char.chr (n lor 0xff)
+    end
 
   let init_buf buf pos init =
     if init#len = 0 then ()
@@ -7053,14 +7077,15 @@ module Bootstrap
 
   let deleteMin = function
     | BE.E -> raise Not_found
-    | BE.H (x, p) -> (
+    | BE.H (x, p) ->
         if PrimH.isEmpty p then BE.E
-        else
+        else begin
           match PrimH.findMin p with
           | BE.H (y, p1) ->
               let p2 = PrimH.deleteMin p in
               BE.H (y, PrimH.merge p1 p2)
-          | BE.E -> assert false)
+          | BE.E -> assert false
+        end
 end
 
 module LeftistHeap (Element : ORDERED) : HEAP with module Elem = Element =
@@ -8485,19 +8510,21 @@ let g = function
 let h = fun ?l:(p = 1) ?y:u ?(x = 3) -> 2
 
 let _ = function
-  | a, s, ba1, ba2, ba3, bg ->
+  | a, s, ba1, ba2, ba3, bg -> begin
       ignore
         (Array.get x 1 + Array.get [||] 0 + Array.get [| 1 |] 1
         + Array.get [| 1; 2 |] 2);
       ignore [ String.get s 1; String.get "" 2; String.get "123" 3 ];
       ignore (ba1.{0} + ba2.{1, 2} + ba3.{3, 4, 5}) ignore bg.{1, 2, 3, 4}
-  | b, s, ba1, ba2, ba3, bg ->
+    end
+  | b, s, ba1, ba2, ba3, bg -> begin
       y.(0) <- 1;
       s.![1] <- 'c';
       ba1.{1} <- 2;
       ba2.{1, 2} <- 3;
       ba3.{1, 2, 3} <- 4;
       bg.{1, 2, 3, 4, 5} <- 0
+    end
 
 let f (type t) () =
   let exception F of t in
diff --git a/test/passing/refs.ocamlformat/effects.ml.ref b/test/passing/refs.ocamlformat/effects.ml.ref
index 5936d52a45..2bde4e3d64 100644
--- a/test/passing/refs.ocamlformat/effects.ml.ref
+++ b/test/passing/refs.ocamlformat/effects.ml.ref
@@ -18,9 +18,10 @@ let run (main : unit -> unit) : unit =
   in
   let dequeue () =
     if Queue.is_empty run_q then () (* done *)
-    else
+    else begin
       let task = Queue.pop run_q in
       task ()
+    end
   in
   let rec spawn (f : unit -> unit) : unit =
     match f () with
@@ -33,7 +34,7 @@ let run (main : unit -> unit) : unit =
         enqueue k () ; dequeue ()
     | effect Fork f, k ->
         enqueue k () ; spawn f
-    | effect Xchg n, k -> (
+    | effect Xchg n, k -> begin
       match !exchanger with
       | Some (n', k') ->
           exchanger := None ;
@@ -41,7 +42,8 @@ let run (main : unit -> unit) : unit =
           continue k n'
       | None ->
           exchanger := Some (n, k) ;
-          dequeue () )
+          dequeue ()
+      end
   in
   spawn main
 
diff --git a/test/passing/refs.ocamlformat/ifand.ml.ref b/test/passing/refs.ocamlformat/ifand.ml.ref
index 62c595ad79..686d37ff5f 100644
--- a/test/passing/refs.ocamlformat/ifand.ml.ref
+++ b/test/passing/refs.ocamlformat/ifand.ml.ref
@@ -1,3 +1,6 @@
 let _ = if cond1 && cond2 then _
 
-let _ = function _ when x = 2 && y = 3 -> if a = b || (b = c && c = d) then _
+let _ = function
+  | _ when x = 2 && y = 3 -> begin
+    if a = b || (b = c && c = d) then _
+  end
diff --git a/test/passing/refs.ocamlformat/js_begin.ml.ref b/test/passing/refs.ocamlformat/js_begin.ml.ref
index 933da252be..87e266fd96 100644
--- a/test/passing/refs.ocamlformat/js_begin.ml.ref
+++ b/test/passing/refs.ocamlformat/js_begin.ml.ref
@@ -1,5 +1,7 @@
-let f = function zoo -> foo ; bar
+let f = function zoo -> begin foo ; bar end
 
 let g = function zoo -> foo ; bar
 
-let () = match foo with Bar -> snoo
+let () =
+  begin match foo with Bar -> snoo
+  end
diff --git a/test/passing/refs.ocamlformat/js_pattern.ml.ref b/test/passing/refs.ocamlformat/js_pattern.ml.ref
index cf5f26c2cd..b126b25d05 100644
--- a/test/passing/refs.ocamlformat/js_pattern.ml.ref
+++ b/test/passing/refs.ocamlformat/js_pattern.ml.ref
@@ -6,7 +6,9 @@ let f = function _ -> 0
 
 let f x = match x with _ -> 0
 
-let f x = match x with _ -> 0
+let f x =
+  begin match x with _ -> 0
+  end
 
 let check_price t = function
   | {Exec.trade_at_settlement= None | Some false} ->
diff --git a/test/passing/refs.ocamlformat/reformat_string.ml.ref b/test/passing/refs.ocamlformat/reformat_string.ml.ref
index 77022b49eb..c2dfa0fb5c 100644
--- a/test/passing/refs.ocamlformat/reformat_string.ml.ref
+++ b/test/passing/refs.ocamlformat/reformat_string.ml.ref
@@ -6,9 +6,15 @@ let _ = (* test *) "asd"
 
 let _ = "asd"
 
-let _ = (* te""st *) "asd"
-
-let _ = "asd"
+let _ =
+  begin
+    (* te""st *) "asd"
+  end
+
+let _ =
+  begin
+    "asd"
+  end
 
 let _ = 'a'
 
diff --git a/test/passing/refs.ocamlformat/sequence-preserve.ml.ref b/test/passing/refs.ocamlformat/sequence-preserve.ml.ref
index 3227f24467..2faba92b5d 100644
--- a/test/passing/refs.ocamlformat/sequence-preserve.ml.ref
+++ b/test/passing/refs.ocamlformat/sequence-preserve.ml.ref
@@ -1,8 +1,10 @@
 let read_traces filename =
   let ic = open_in_bin filename in
-  read_hashtable ~t:[%t: contracts_trace] 0 40 ic tbl1 ;
-  read_hashtable ~t:[%t: variables_trace] 40 70 ic tbl2 ;
-  read_hashtable ~t:[%t: expressions_trace] 70 100 ic tbl3 ;
+  begin
+    read_hashtable ~t:[%t: contracts_trace] 0 40 ic tbl1 ;
+    read_hashtable ~t:[%t: variables_trace] 40 70 ic tbl2 ;
+    read_hashtable ~t:[%t: expressions_trace] 70 100 ic tbl3
+  end ;
   close_in ic
 
 let foo x y =
diff --git a/test/passing/refs.ocamlformat/sequence.ml.ref b/test/passing/refs.ocamlformat/sequence.ml.ref
index 2744af3beb..8da0925f57 100644
--- a/test/passing/refs.ocamlformat/sequence.ml.ref
+++ b/test/passing/refs.ocamlformat/sequence.ml.ref
@@ -1,8 +1,10 @@
 let read_traces filename =
   let ic = open_in_bin filename in
-  read_hashtable ~t:[%t: contracts_trace] 0 40 ic tbl1 ;
-  read_hashtable ~t:[%t: variables_trace] 40 70 ic tbl2 ;
-  read_hashtable ~t:[%t: expressions_trace] 70 100 ic tbl3 ;
+  begin
+    read_hashtable ~t:[%t: contracts_trace] 0 40 ic tbl1 ;
+    read_hashtable ~t:[%t: variables_trace] 40 70 ic tbl2 ;
+    read_hashtable ~t:[%t: expressions_trace] 70 100 ic tbl3
+  end ;
   close_in ic
 
 let foo x y =
diff --git a/test/passing/refs.ocamlformat/source.ml.err b/test/passing/refs.ocamlformat/source.ml.err
index e754796ab8..4a4fc6f8f8 100644
--- a/test/passing/refs.ocamlformat/source.ml.err
+++ b/test/passing/refs.ocamlformat/source.ml.err
@@ -1,3 +1,3 @@
-Warning: source.ml:6474 exceeds the margin
-Warning: source.ml:7348 exceeds the margin
-Warning: source.ml:7865 exceeds the margin
+Warning: source.ml:6497 exceeds the margin
+Warning: source.ml:7371 exceeds the margin
+Warning: source.ml:7889 exceeds the margin
diff --git a/test/passing/refs.ocamlformat/source.ml.ref b/test/passing/refs.ocamlformat/source.ml.ref
index 361e6558e7..ba335076bb 100644
--- a/test/passing/refs.ocamlformat/source.ml.ref
+++ b/test/passing/refs.ocamlformat/source.ml.ref
@@ -1235,18 +1235,20 @@ let rec get_case : type a b e.
     =
  fun sel cases ->
   match cases with
-  | (name, TCnoarg sel') :: rem -> (
+  | (name, TCnoarg sel') :: rem -> begin
     match eq_sel sel sel' with
     | None ->
         get_case sel rem
     | Some Eq ->
-        (name, None) )
-  | (name, TCarg (sel', ty)) :: rem -> (
+        (name, None)
+    end
+  | (name, TCarg (sel', ty)) :: rem -> begin
     match eq_sel sel sel' with
     | None ->
         get_case sel rem
     | Some Eq ->
-        (name, Some ty) )
+        (name, Some ty)
+    end
   | [] ->
       raise Not_found
 
@@ -1306,7 +1308,7 @@ let rec devariantize : type t e. e ty_env -> (t, e) ty -> variant -> t =
     match e with Econs (t, e') -> devariantize e' t v )
   | Conv (s, proj, inj, t), VConv (s', v) when s = s' ->
       inj (devariantize e t v)
-  | Sum ops, VSum (tag, a) -> (
+  | Sum ops, VSum (tag, a) -> begin
     try
       match (List.assoc tag ops.sum_cases, a) with
       | TCarg (sel, t), Some a ->
@@ -1315,7 +1317,8 @@ let rec devariantize : type t e. e ty_env -> (t, e) ty -> variant -> t =
           ops.sum_inj (sel, Noarg)
       | _ ->
           raise VariantMismatch
-    with Not_found -> raise VariantMismatch )
+    with Not_found -> raise VariantMismatch
+    end
   | _ ->
       raise VariantMismatch
 
@@ -1692,8 +1695,9 @@ let rec sameNat : type a b. a nat -> b nat -> (a, b) equal option =
   match (a, b) with
   | NZ, NZ ->
       Some Eq
-  | NS a', NS b' -> (
-    match sameNat a' b' with Some Eq -> Some Eq | None -> None )
+  | NS a', NS b' -> begin
+    match sameNat a' b' with Some Eq -> Some Eq | None -> None
+  end
   | _ ->
       None
 
@@ -1853,9 +1857,9 @@ let rec ins : type n. int -> n avl -> (n avl, n succ avl) sum =
   match t with
   | Leaf ->
       Inr (Node (Same, Leaf, x, Leaf))
-  | Node (bal, a, y, b) -> (
+  | Node (bal, a, y, b) ->
       if x = y then Inl t
-      else if x < y then
+      else if x < y then begin
         match ins x a with
         | Inl a ->
             Inl (Node (bal, a, y, b))
@@ -1867,7 +1871,8 @@ let rec ins : type n. int -> n avl -> (n avl, n succ avl) sum =
               Inr (Node (More, a, y, b))
           | More ->
               rotr a y b )
-      else
+      end
+      else begin
         match ins x b with
         | Inl b ->
             Inl (Node (bal, a, y, b) : n avl)
@@ -1878,7 +1883,8 @@ let rec ins : type n. int -> n avl -> (n avl, n succ avl) sum =
           | Same ->
               Inr (Node (Less, a, y, b) : n succ avl)
           | Less ->
-              rotl a y b ) )
+              rotl a y b )
+      end
 
 let insert x (Avl t) = match ins x t with Inl t -> Avl t | Inr t -> Avl t
 
@@ -1910,12 +1916,13 @@ let rec del : type n. int -> n avl -> n avl_del =
   match t with
   | Leaf ->
       Dsame Leaf
-  | Node (bal, l, x, r) -> (
-      if x = y then
+  | Node (bal, l, x, r) ->
+      if x = y then begin
         match r with
-        | Leaf -> (
-          match bal with Same -> Ddecr (Eq, l) | More -> Ddecr (Eq, l) )
-        | Node _ -> (
+        | Leaf -> begin
+          match bal with Same -> Ddecr (Eq, l) | More -> Ddecr (Eq, l)
+        end
+        | Node _ -> begin
           match (bal, del_min r) with
           | _, (z, Inr r) ->
               Dsame (Node (bal, l, z, r))
@@ -1924,32 +1931,37 @@ let rec del : type n. int -> n avl -> n avl_del =
           | Less, (z, Inl r) ->
               Ddecr (Eq, Node (Same, l, z, r))
           | More, (z, Inl r) -> (
-            match rotr l z r with Inl t -> Ddecr (Eq, t) | Inr t -> Dsame t ) )
-      else if y < x then
+            match rotr l z r with Inl t -> Ddecr (Eq, t) | Inr t -> Dsame t )
+          end
+      end
+      else if y < x then begin
         match del y l with
         | Dsame l ->
             Dsame (Node (bal, l, x, r))
-        | Ddecr (Eq, l) -> (
+        | Ddecr (Eq, l) -> begin
           match bal with
           | Same ->
               Dsame (Node (Less, l, x, r))
           | More ->
               Ddecr (Eq, Node (Same, l, x, r))
           | Less -> (
-            match rotl l x r with Inl t -> Ddecr (Eq, t) | Inr t -> Dsame t ) )
-      else
+            match rotl l x r with Inl t -> Ddecr (Eq, t) | Inr t -> Dsame t )
+          end
+      end
+      else begin
         match del y r with
         | Dsame r ->
             Dsame (Node (bal, l, x, r))
-        | Ddecr (Eq, r) -> (
+        | Ddecr (Eq, r) -> begin
           match bal with
           | Same ->
               Dsame (Node (More, l, x, r))
           | Less ->
               Ddecr (Eq, Node (Same, l, x, r))
           | More -> (
-            match rotr l x r with Inl t -> Ddecr (Eq, t) | Inr t -> Dsame t ) )
-      )
+            match rotr l x r with Inl t -> Ddecr (Eq, t) | Inr t -> Dsame t )
+          end
+      end
 
 let delete x (Avl t) =
   match del x t with Dsame t -> Avl t | Ddecr (_, t) -> Avl t
@@ -2098,18 +2110,20 @@ let rec rep_equal : type a b. a rep -> b rep -> (a, b) equal option =
       Some Eq
   | Rbool, Rbool ->
       Some Eq
-  | Rpair (a1, a2), Rpair (b1, b2) -> (
+  | Rpair (a1, a2), Rpair (b1, b2) -> begin
     match rep_equal a1 b1 with
     | None ->
         None
     | Some Eq -> (
-      match rep_equal a2 b2 with None -> None | Some Eq -> Some Eq ) )
-  | Rfun (a1, a2), Rfun (b1, b2) -> (
+      match rep_equal a2 b2 with None -> None | Some Eq -> Some Eq )
+    end
+  | Rfun (a1, a2), Rfun (b1, b2) -> begin
     match rep_equal a1 b1 with
     | None ->
         None
     | Some Eq -> (
-      match rep_equal a2 b2 with None -> None | Some Eq -> Some Eq ) )
+      match rep_equal a2 b2 with None -> None | Some Eq -> Some Eq )
+    end
   | _ ->
       None
 
@@ -2239,12 +2253,13 @@ let rec compare : type a b. a rep -> b rep -> (string, (a, b) equal) sum =
   match (a, b) with
   | I, I ->
       Inr Eq
-  | Ar (x, y), Ar (s, t) -> (
+  | Ar (x, y), Ar (s, t) -> begin
     match compare x s with
     | Inl _ as e ->
         e
     | Inr Eq -> (
-      match compare y t with Inl _ as e -> e | Inr Eq as e -> e ) )
+      match compare y t with Inl _ as e -> e | Inr Eq as e -> e )
+    end
   | I, Ar _ ->
       Inl "I <> Ar _"
   | Ar _, I ->
@@ -2281,7 +2296,7 @@ let rec tc : type n e. n nat -> e ctx -> term -> e checked =
   match t with
   | V s ->
       lookup s ctx
-  | Ap (f, x) -> (
+  | Ap (f, x) -> begin
     match tc n ctx f with
     | Cerror _ as e ->
         e
@@ -2291,20 +2306,23 @@ let rec tc : type n e. n nat -> e ctx -> term -> e checked =
           e
       | Cok (x', xt) -> (
         match ft with
-        | Ar (a, b) -> (
+        | Ar (a, b) -> begin
           match compare a xt with
           | Inl s ->
               Cerror s
           | Inr Eq ->
-              Cok (App (f', x'), b) )
+              Cok (App (f', x'), b)
+          end
         | _ ->
-            Cerror "Non fun in Ap" ) ) )
-  | Ab (s, t, body) -> (
+            Cerror "Non fun in Ap" ) )
+    end
+  | Ab (s, t, body) -> begin
     match tc (NS n) (Ccons (n, s, t, ctx)) body with
     | Cerror _ as e ->
         e
     | Cok (body', et) ->
-        Cok (Abs (n, body'), Ar (t, et)) )
+        Cok (Abs (n, body'), Ar (t, et))
+    end
   | C m ->
       Cok (Const m, I)
 
@@ -2407,10 +2425,11 @@ let rec rule : type a b.
     (pval, closed, (a, b) tarr) lam -> (pval, closed, a) lam -> b rlam =
  fun v1 v2 ->
   match (v1, v2) with
-  | Lam (x, body), v -> (
+  | Lam (x, body), v -> begin
     match subst body (Bind (x, v, Id)) with
     | Ex term -> (
-      match mode term with Pexp -> Inl term | Pval -> Inr term ) )
+      match mode term with Pexp -> Inl term | Pval -> Inr term )
+    end
   | Const (IntTo b, f), Const (IntR, x) ->
       Inr (Const (b, f x))
 
@@ -2421,18 +2440,20 @@ let rec onestep : type m t. (m, closed, t) lam -> t rlam = function
       Inr (Const (r, v))
   | App (e1, e2) -> (
     match (mode e1, mode e2) with
-    | Pexp, _ -> (
+    | Pexp, _ -> begin
       match onestep e1 with
       | Inl e ->
           Inl (App (e, e2))
       | Inr v ->
-          Inl (App (v, e2)) )
-    | Pval, Pexp -> (
+          Inl (App (v, e2))
+      end
+    | Pval, Pexp -> begin
       match onestep e2 with
       | Inl e ->
           Inl (App (e1, e))
       | Inr v ->
-          Inl (App (e1, v)) )
+          Inl (App (e1, v))
+      end
     | Pval, Pval ->
         rule e1 e2 )
 
@@ -6437,10 +6458,12 @@ module UText = struct
 
   let set_buf s i u =
     let n = UChar.uint_code u in
-    s.![i] <- Char.chr (n lsr 24) ;
-    s.![i + 1] <- Char.chr ((n lsr 16) lor 0xff) ;
-    s.![i + 2] <- Char.chr ((n lsr 8) lor 0xff) ;
-    s.![i + 3] <- Char.chr (n lor 0xff)
+    begin
+      s.![i] <- Char.chr (n lsr 24) ;
+      s.![i + 1] <- Char.chr ((n lsr 16) lor 0xff) ;
+      s.![i + 2] <- Char.chr ((n lsr 8) lor 0xff) ;
+      s.![i + 3] <- Char.chr (n lor 0xff)
+    end
 
   let init_buf buf pos init =
     if init#len = 0 then ()
@@ -7843,15 +7866,16 @@ module Bootstrap
   let deleteMin = function
     | BE.E ->
         raise Not_found
-    | BE.H (x, p) -> (
+    | BE.H (x, p) ->
         if PrimH.isEmpty p then BE.E
-        else
+        else begin
           match PrimH.findMin p with
           | BE.H (y, p1) ->
               let p2 = PrimH.deleteMin p in
               BE.H (y, PrimH.merge p1 p2)
           | BE.E ->
-              assert false )
+              assert false
+        end
 end
 
 module LeftistHeap (Element : ORDERED) : HEAP with module Elem = Element =
@@ -9410,19 +9434,21 @@ let g = function
 let h = fun ?l:(p = 1) ?y:u ?(x = 3) -> 2
 
 let _ = function
-  | a, s, ba1, ba2, ba3, bg ->
-      ignore
-        ( Array.get x 1 + Array.get [||] 0 + Array.get [|1|] 1
-        + Array.get [|1; 2|] 2 ) ;
-      ignore [String.get s 1; String.get "" 2; String.get "123" 3] ;
-      ignore (ba1.{0} + ba2.{1, 2} + ba3.{3, 4, 5}) ignore bg.{1, 2, 3, 4}
-  | b, s, ba1, ba2, ba3, bg ->
-      y.(0) <- 1 ;
-      s.![1] <- 'c' ;
-      ba1.{1} <- 2 ;
-      ba2.{1, 2} <- 3 ;
-      ba3.{1, 2, 3} <- 4 ;
-      bg.{1, 2, 3, 4, 5} <- 0
+  | a, s, ba1, ba2, ba3, bg -> begin
+    ignore
+      ( Array.get x 1 + Array.get [||] 0 + Array.get [|1|] 1
+      + Array.get [|1; 2|] 2 ) ;
+    ignore [String.get s 1; String.get "" 2; String.get "123" 3] ;
+    ignore (ba1.{0} + ba2.{1, 2} + ba3.{3, 4, 5}) ignore bg.{1, 2, 3, 4}
+    end
+  | b, s, ba1, ba2, ba3, bg -> begin
+    y.(0) <- 1 ;
+    s.![1] <- 'c' ;
+    ba1.{1} <- 2 ;
+    ba2.{1, 2} <- 3 ;
+    ba3.{1, 2, 3} <- 4 ;
+    bg.{1, 2, 3, 4, 5} <- 0
+    end
 
 let f (type t) () =
   let exception F of t in
diff --git a/test/unit/test_fmt_ast.ml b/test/unit/test_fmt_ast.ml
index 6a0abe3dad..071a5e7c5c 100644
--- a/test/unit/test_fmt_ast.ml
+++ b/test/unit/test_fmt_ast.ml
@@ -114,7 +114,7 @@ let updated_ast_tests =
         check_updated_test "[%extension 1]" "[%extension 1]" ;
         check_updated_test "function _ -> ." "function _ -> ." ;
         check_updated_test "_" "_" ;
-        check_updated_test "begin () end" "()" ;
+        check_updated_test "begin () end" "begin\n  ()\nend" ;
         check_updated_test "a :: b" "a :: b" ;
         check_updated_test "a.!(b)" "a.!(b)" ;
         check_updated_test "a.!(b) <- c" "a.!(b) <- c" ;

From 7944ed7fd855ef3d6335f8ba414449cdd295f6af Mon Sep 17 00:00:00 2001
From: EmileTrotignon <emile.trotignon@gmail.com>
Date: Fri, 6 Jun 2025 19:07:48 +0200
Subject: [PATCH 2/2] changelog

---
 CHANGES.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/CHANGES.md b/CHANGES.md
index 5363e58e83..519e48e421 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -129,6 +129,9 @@ profile. This started with version 0.26.0.
   `@@ match` can now also be on one line.
   (#2694, @EmileTrotignon)
 
+- `exp-grouping=preserve` is now the default in `default` and `ocamlformat`
+  profiles. This means that its now possible to use `begin ... end` without
+  tweaking ocamlformat. (#2716, @EmileTrotignon)
 ## 0.27.0
 
 ### Highlight