New value 'vertical' for option 'break-cases'

CHANGES.md

@@ -28,6 +28,7 @@
 - Add a `break-colon` option to decide whether to break before or after the `:` symbol in value binding declarations and type constraints. This behavior is no longer ensured by `ocp-indent-compat`. (#2149, @gpetiot)
 - Format `.mld` files as odoc documentation files (#2008, @gpetiot)
 - New value `vertical` for option `if-then-else` (#2174, @gpetiot)
+- New value `vertical` for option `break-cases` (#2176, @gpetiot)
 
 ## 0.24.1 (2022-07-18)
 

lib/Conf.ml

@@ -17,7 +17,8 @@ type fmt_opts =
   { align_pattern_matching_bar: [`Paren | `Keyword]
   ; assignment_operator: [`Begin_line | `End_line]
   ; break_before_in: [`Fit_or_vertical | `Auto]
-  ; break_cases: [`Fit | `Nested | `Toplevel | `Fit_or_vertical | `All]
+  ; break_cases:
+      [`Fit | `Nested | `Toplevel | `Fit_or_vertical | `Vertical | `All]
   ; break_collection_expressions: [`Wrap | `Fit_or_vertical]
   ; break_colon: [`Before | `After]
   ; break_infix: [`Wrap | `Fit_or_vertical]
@@ -273,6 +274,8 @@ module Formatting = struct
       ; C.Value.make ~name:"fit-or-vertical" `Fit_or_vertical
           "$(b,fit-or-vertical) tries to fit all or-patterns on the same \
            line, otherwise breaks."
+      ; C.Value.make ~name:"vertical" `Vertical
+          "$(b,vertical) vertically breaks branches."
       ; C.Value.make ~name:"all" `All
           "$(b,all) forces all pattern matches to break across lines." ]
     in

lib/Conf.mli

@@ -16,7 +16,8 @@ type fmt_opts =
   { align_pattern_matching_bar: [`Paren | `Keyword]
   ; assignment_operator: [`Begin_line | `End_line]
   ; break_before_in: [`Fit_or_vertical | `Auto]
-  ; break_cases: [`Fit | `Nested | `Toplevel | `Fit_or_vertical | `All]
+  ; break_cases:
+      [`Fit | `Nested | `Toplevel | `Fit_or_vertical | `Vertical | `All]
   ; break_collection_expressions: [`Wrap | `Fit_or_vertical]
   ; break_colon: [`Before | `After]
   ; break_infix: [`Wrap | `Fit_or_vertical]

lib/Fmt_ast.ml

@@ -1092,7 +1092,7 @@ and fmt_pattern ?ext c ?pro ?parens ?(box = false)
       in
       let open_box =
         match c.conf.fmt_opts.break_cases with
-        | `Fit_or_vertical -> open_hvbox
+        | `Fit_or_vertical | `Vertical -> open_hvbox
         | `Fit | `Nested | `Toplevel | `All -> open_hovbox
       in
       hvbox 0
@@ -2252,7 +2252,8 @@ and fmt_expression c ?(box = true) ?pro ?epi ?eol ?parens ?(indent_wrap = 0)
   | Pexp_try (e0, [{pc_lhs; pc_guard; pc_rhs}])
     when Poly.(
            c.conf.fmt_opts.single_case = `Compact
-           && c.conf.fmt_opts.break_cases <> `All ) ->
+           && c.conf.fmt_opts.break_cases <> `All
+           && c.conf.fmt_opts.break_cases <> `Vertical ) ->
       (* side effects of Cmts.fmt_before before [fmt_pattern] is important *)
       let xpc_rhs = sub_exp ~ctx pc_rhs in
       let leading_cmt = Cmts.fmt_before c pc_lhs.ppat_loc in

lib/Params.ml

@@ -71,7 +71,9 @@ let get_or_pattern_sep ?(cmts_before = false) ?(space = false) (c : Conf.t)
     | `Nested -> break nspaces 0 $ str "| "
     | _ -> (
         let nspaces =
-          match c.fmt_opts.break_cases with `All -> 1000 | _ -> nspaces
+          match c.fmt_opts.break_cases with
+          | `All | `Vertical -> 1000
+          | _ -> nspaces
         in
         match c.fmt_opts.indicate_nested_or_patterns with
         | `Space ->
@@ -154,6 +156,16 @@ let get_cases (c : Conf.t) ~first ~indent ~parens_branch ~xbch =
       ; open_paren_branch
       ; break_after_opening_paren= fmt "@ "
       ; close_paren_branch }
+  | `Vertical ->
+      { leading_space= break_unless_newline 1000 0
+      ; bar= str "| "
+      ; box_all= hvbox indent
+      ; box_pattern_arrow= hovbox 0
+      ; break_before_arrow= fmt "@;<1 2>"
+      ; break_after_arrow= fmt_if (not parens_branch) "@;<0 3>"
+      ; open_paren_branch
+      ; break_after_opening_paren= break 1000 0
+      ; close_paren_branch }
 
 let wrap_collec c ~space_around opn cls =
   if space_around then wrap_k (str opn $ char ' ') (break 1 0 $ str cls)

ocamlformat-help.txt

@@ -59,16 +59,17 @@ OPTIONS (CODE FORMATTING STYLE)
            auto will only break the line if the in keyword does not fit on
            the previous line. The default value is fit-or-vertical.
 
-       --break-cases={fit|nested|toplevel|fit-or-vertical|all}
+       --break-cases={fit|nested|toplevel|fit-or-vertical|vertical|all}
            Break pattern match cases. Specifying fit lets pattern matches
            break at the margin naturally. nested forces a break after nested
            or-patterns to highlight the case body. Note that with nested, the
            indicate-nested-or-patterns option is not needed, and so ignored.
            toplevel forces top-level cases (i.e. not nested or-patterns) to
            break across lines, otherwise break naturally at the margin.
            fit-or-vertical tries to fit all or-patterns on the same line,
-           otherwise breaks. all forces all pattern matches to break across
-           lines. The default value is fit.
+           otherwise breaks. vertical vertically breaks branches. all forces
+           all pattern matches to break across lines. The default value is
+           fit.
 
        --break-collection-expressions={fit-or-vertical|wrap}
            Break collection expressions (lists and arrays) elements by

test/passing/dune.inc

@@ -455,6 +455,27 @@
  (package ocamlformat)
  (action (diff tests/break_cases-toplevel.ml.err break_cases-toplevel.ml.stderr)))
 
+(rule
+ (deps tests/.ocamlformat )
+ (enabled_if (<> %{os_type} Win32))
+ (package ocamlformat)
+ (action
+  (with-stdout-to break_cases-vertical.ml.stdout
+   (with-stderr-to break_cases-vertical.ml.stderr
+     (run %{bin:ocamlformat} --margin-check --break-cases=vertical %{dep:tests/break_cases.ml})))))
+
+(rule
+ (alias runtest)
+ (enabled_if (<> %{os_type} Win32))
+ (package ocamlformat)
+ (action (diff tests/break_cases-vertical.ml.ref break_cases-vertical.ml.stdout)))
+
+(rule
+ (alias runtest)
+ (enabled_if (<> %{os_type} Win32))
+ (package ocamlformat)
+ (action (diff tests/break_cases-vertical.ml.err break_cases-vertical.ml.stderr)))
+
 (rule
  (deps tests/.ocamlformat )
  (package ocamlformat)

test/passing/tests/break_cases-vertical.ml.enabled-if

@@ -0,0 +1 @@
+(<> %{os_type} Win32)

test/passing/tests/break_cases-vertical.ml.err

@@ -0,0 +1,4 @@
+Warning: tests/break_cases.ml:80 exceeds the margin
+Warning: tests/break_cases.ml:159 exceeds the margin
+Warning: tests/break_cases.ml:273 exceeds the margin
+Warning: tests/break_cases.ml:281 exceeds the margin

test/passing/tests/break_cases-vertical.ml.opts

@@ -0,0 +1 @@
+--break-cases=vertical