RFC: Make it possible to disable line wrapping in tests (#10841)

* feat(test): Make it possible to disable line wrapping

Sometimes cram tests are not reproducible if different platforms output
different length errors, in which case even editing out the errors with
common tools like `sed` does not help as the wrapping happens before the
`sed` invocation runs, thus the message is split over multiple lines.

This introduces an option to disable the automatic wrapping of lines.

---------

Signed-off-by: Marek Kubica <[email protected]>

Author: Leonidas-from-XIV

otherlibs/stdune/src/ansi_color.ml

@@ -494,6 +494,13 @@ let rec tag_handler buf current_styles ppf (styles : Style.t list) pp =
     (Style.escape_sequence_buf buf (current_styles :> Style.t list))
 ;;
 
+let skip_line_break =
+  lazy
+    (match Sys.getenv_opt "DUNE_CONFIG__SKIP_LINE_BREAK" with
+     | Some "enabled" -> true
+     | _ -> false)
+;;
+
 let make_printer supports_color ppf =
   let f =
     lazy
@@ -504,6 +511,7 @@ let make_printer supports_color ppf =
        else Pp.to_fmt ppf)
   in
   Staged.stage (fun pp ->
+    if Lazy.force skip_line_break then Format.pp_set_margin ppf Format.pp_infinity;
     Lazy.force f pp;
     Format.pp_print_flush ppf ())
 ;;

otherlibs/stdune/src/format.ml

@@ -0,0 +1,4 @@
+(* added in OCaml 5.2 *)
+let[@warning "-32"] pp_infinity = Int.max_int
+
+include Stdlib.Format

otherlibs/stdune/src/format.mli

@@ -0,0 +1,3 @@
+val pp_infinity : int
+
+include module type of Stdlib.Format

otherlibs/stdune/src/int.ml

@@ -47,3 +47,4 @@ module Infix = Comparator.Operators (T)
 let of_string s = int_of_string_opt s
 let shift_left = Stdlib.Int.shift_left
 let shift_right = Stdlib.Int.shift_right
+let max_int = Stdlib.Int.max_int

otherlibs/stdune/src/int.mli

@@ -15,3 +15,4 @@ module Infix : Comparator.OPS with type t = t
 
 val shift_left : t -> t -> t
 val shift_right : t -> t -> t
+val max_int : t

otherlibs/stdune/src/stdune.ml

@@ -13,6 +13,7 @@ module Exn = Exn
 module Exn_with_backtrace = Exn_with_backtrace
 module Filename = Filename
 module Filename_set = Filename_set
+module Format = Format
 module Hashtbl = Hashtbl
 module Table = Table
 module Int = Int

test/blackbox-tests/test-cases/long-lines.t

@@ -0,0 +1,47 @@
+Test the behavior of long lines
+
+In the default output, user input affects on which lines which of the output
+lines appear. For example, with a short project name, the line wraps later:
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.17)
+  > (package
+  >  (name short))
+  > EOF
+  $ dune build
+  Error: The package short does not have any user defined stanzas attached to
+  it. If this is intentional, add (allow_empty) to the package definition in
+  the dune-project file
+  -> required by _build/default/short.install
+  -> required by alias all
+  -> required by alias default
+  [1]
+
+With a long project name, there are less words on the line and thus it wraps in
+a different position:
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.17)
+  > (package
+  >  (name verylongnamethatcauseslinewrappingincases))
+  > EOF
+  $ dune build
+  Error: The package verylongnamethatcauseslinewrappingincases does not have
+  any user defined stanzas attached to it. If this is intentional, add
+  (allow_empty) to the package definition in the dune-project file
+  -> required by
+     _build/default/verylongnamethatcauseslinewrappingincases.install
+  -> required by alias all
+  -> required by alias default
+  [1]
+
+Disabling line breaks should thus only break lines where there are explicit
+line breaks in the input and not when the line gets too long.
+
+  $ export DUNE_CONFIG__SKIP_LINE_BREAK=enabled
+  $ dune build
+  Error: The package verylongnamethatcauseslinewrappingincases does not have any user defined stanzas attached to it. If this is intentional, add (allow_empty) to the package definition in the dune-project file
+  -> required by _build/default/verylongnamethatcauseslinewrappingincases.install
+  -> required by alias all
+  -> required by alias default
+  [1]