Improve indentation of end keyword in begin end enclosed submatch

CHANGES.md

@@ -10,6 +10,43 @@ profile. This started with version 0.26.0.
 
 - Fix dropped comment in `(function _ -> x (* cmt *))` (#2739, @Julow)
 
+- \* `cases-matching-exp-indent=compact` does not impact `begin end` nodes that
+  don't have a match inside. (#2742, @EmileTrotignon)
+  ```ocaml
+  (* before *)
+  begin match () with
+  | () -> begin
+    f x
+  end
+  end
+  (* after *)
+  begin match () with
+  | () -> begin
+      f x
+    end
+  end
+  ```
+
+
+### Changed
+
+- indentation of the `end` keyword in a match-case is now always at least 2. (#2742, @EmileTrotignon)
+  ```ocaml
+  (* before *)
+  begin match () with
+  | () -> begin
+    match () with
+    | () -> ()
+  end
+  end
+  (* after *)
+  begin match () with
+  | () -> begin
+    match () with
+    | () -> ()
+    end
+  end
+  ```
 ## 0.28.1
 
 ### Highlight
@@ -38,7 +75,7 @@ profile. This started with version 0.26.0.
 ### Added
 
 - Added option `module-indent` option (#2711, @HPRIOR) to control the indentation
-  of items within modules. This affects modules and signatures. For example, 
+  of items within modules. This affects modules and signatures. For example,
   module-indent=4:
   ```ocaml
   module type M = sig
@@ -146,7 +183,7 @@ profile. This started with version 0.26.0.
 - Fix a crash where `type%e nonrec t = t` was formatted as `type nonrec%e t = t`,
   which is invalid syntax. (#2712, @EmileTrotignon)
 
-- Fix commandline parsing being quadratic in the number of arguments 
+- Fix commandline parsing being quadratic in the number of arguments
   (#2724, @let-def)
 
 - \* Fix `;;` being added after a documentation comment (#2683, @EmileTrotignon)

lib/Params.ml

@@ -512,7 +512,9 @@ let get_cases (c : Conf.t) ~fmt_infix_ext_attrs ~ctx ~first ~last
                   Pexp_function _ | Pexp_match _ | Pexp_try _ | Pexp_let _
               ; _ }
           | Lb {pvb_body= Pfunction_cases _; _} )
-        , (Pexp_match _ | Pexp_try _ | Pexp_beginend _) ) ) ->
+        , ( Pexp_match _ | Pexp_try _
+          | Pexp_beginend ({pexp_desc= Pexp_match _ | Pexp_try _; _}, _) ) )
+      ) ->
         2
     | _, _ -> c.fmt_opts.cases_exp_indent.v
   in
@@ -542,9 +544,7 @@ let get_cases (c : Conf.t) ~fmt_infix_ext_attrs ~ctx ~first ~last
       ; _ }
       when not cmts_before ->
         let close_paren =
-          let offset =
-            match c.fmt_opts.break_cases.v with `Nested -> 0 | _ -> -2
-          in
+          let offset = if indent >= 2 then 2 - indent else 0 in
           fits_breaks " end" ~level:1 ~hint:(1000, offset) "end"
         in
         ( break 1 0 $ fmt_infix_ext_attrs ~pro:(str "begin") infix_ext_attrs

test/passing/gen/dune.inc

@@ -872,6 +872,24 @@
  (package ocamlformat)
  (action (diff cases_exp_grouping.ml.err cases_exp_grouping.ml.stderr)))
 
+(rule
+ (deps .ocamlformat)
+ (package ocamlformat)
+ (action
+  (with-stdout-to cases_exp_indent.ml.stdout
+   (with-stderr-to cases_exp_indent.ml.stderr
+     (run %{bin:ocamlformat} --name cases_exp_indent.ml --margin-check --nested-match=align --cases-exp-indent=4 %{dep:../tests/cases_exp_indent.ml})))))
+
+(rule
+ (alias runtest)
+ (package ocamlformat)
+ (action (diff cases_exp_indent.ml.ref cases_exp_indent.ml.stdout)))
+
+(rule
+ (alias runtest)
+ (package ocamlformat)
+ (action (diff cases_exp_indent.ml.err cases_exp_indent.ml.stderr)))
+
 (rule
  (deps .ocamlformat)
  (enabled_if (<> %{os_type} Win32))

test/passing/refs.ahrefs/cases_exp_grouping.ml.ref

@@ -8,7 +8,7 @@ let _ =
     | B -> fooooooooooooo
     | C -> fooooooooooooo
     | D -> fooooooooooooo
-  end
+    end
 [@@ocamlformat "break-cases=fit"]
 
 let _ =
@@ -37,59 +37,59 @@ let _ =
   | A -> begin
     match B with
     | A -> fooooooooooooo
-  end
+    end
   | A -> begin
     match B with
     | A -> fooooooooooooo
     | B -> fooooooooooooo
-  end
+    end
   | A -> begin
     match B with
     | A -> fooooooooooooo
     | B -> fooooooooooooo
     | C -> fooooooooooooo
     | D -> fooooooooooooo
-  end
+    end
 [@@ocamlformat "break-cases=toplevel"]
 
 let _ =
   match x with
   | A -> begin
     match B with
     | A -> fooooooooooooo
-  end
+    end
   | A -> begin
     match B with
     | A -> fooooooooooooo
     | B -> fooooooooooooo
-  end
+    end
   | A -> begin
     match B with
     | A -> fooooooooooooo
     | B -> fooooooooooooo
     | C -> fooooooooooooo
     | D -> fooooooooooooo
-  end
+    end
 [@@ocamlformat "break-cases=fit-or-vertical"]
 
 let _ =
   match x with
   | A -> begin
     match B with
     | A -> fooooooooooooo
-  end
+    end
   | A -> begin
     match B with
     | A -> fooooooooooooo
     | B -> fooooooooooooo
-  end
+    end
   | A -> begin
     match B with
     | A -> fooooooooooooo
     | B -> fooooooooooooo
     | C -> fooooooooooooo
     | D -> fooooooooooooo
-  end
+    end
 [@@ocamlformat "break-cases=all"]
 
 let a =

test/passing/refs.ahrefs/cases_exp_indent.ml.ref

@@ -0,0 +1,23 @@
+[@@@ocamlformat "break-cases=fit-or-vertical"]
+
+let () =
+  begin match () with
+  | () -> begin
+    aaaaaaaaaaa aaaaaaaaaaaaaaa aaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaa
+      aaaaaaaaaaaaa ()
+  end
+  | () ->
+    aaaaaaaaaaa aaaaaaaaaaaaaaa aaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaa
+      aaaaaaaaaaaaa ()
+  | () -> begin
+    match () with
+    | () -> ()
+  end
+  | () ->
+    (match () with
+    | () -> ())
+  | () -> begin
+    match () with
+    | () -> ()
+  end
+  end

test/passing/refs.ahrefs/effects.ml.ref

@@ -42,7 +42,7 @@ let run (main : unit -> unit) : unit =
       | None ->
         exchanger := Some (n, k);
         dequeue ()
-    end
+      end
   in
   spawn main
 

test/passing/refs.ahrefs/exp_grouping.ml.ref

@@ -284,19 +284,19 @@ let _ =
   | A -> begin
     match B with
     | A -> fooooooooooooo
-  end
+    end
   | A -> begin
     match B with
     | A -> fooooooooooooo
     | B -> fooooooooooooo
-  end
+    end
   | A -> begin
     match B with
     | A -> fooooooooooooo
     | B -> fooooooooooooo
     | C -> fooooooooooooo
     | D -> fooooooooooooo
-  end
+    end
 
 let () =
   begin

test/passing/refs.ahrefs/js_begin.ml.ref

@@ -2,7 +2,7 @@ let f = function
   | zoo -> begin
     foo;
     bar
-  end
+    end
 let g = function
   | zoo ->
     foo;