[sledge] Use the configured margin when formatting failure messages

Reviewed By: bennostein

Differential Revision: D17801934

fbshipit-source-id: af7acec9b

sledge/src/import/import.ml

@@ -65,9 +65,14 @@ let warn fmt =
       Format.pp_force_newline fs () )
     fs fmt
 
-let raisef exn fmt =
+let raisef ?margin exn fmt =
   let bt = Caml.Printexc.get_raw_backtrace () in
   let fs = Format.str_formatter in
+  ( match margin with
+  | Some m ->
+      Format.pp_set_margin fs m ;
+      Format.pp_set_max_indent fs (m - 1)
+  | None -> () ) ;
   Format.pp_open_box fs 2 ;
   Format.kfprintf
     (fun fs () ->

sledge/src/import/import.mli

@@ -77,7 +77,7 @@ type ('a, 'b) fmt = ('a, Formatter.t, unit, 'b) format4
 
 exception Unimplemented of string
 
-val raisef : (string -> exn) -> ('a, unit -> _) fmt -> 'a
+val raisef : ?margin:int -> (string -> exn) -> ('a, unit -> _) fmt -> 'a
 (** Take a function from a string message to an exception, and a format
     string with the additional arguments it specifies, and then call the
     function on the formatted string and raise the returned exception. *)

sledge/src/trace/trace.ml

@@ -167,7 +167,8 @@ let retn mod_name fun_name k result =
   result
 
 let fail fmt =
-  raisef
+  let margin = Format.pp_get_margin fs () in
+  raisef ~margin
     (fun msg ->
       Format.fprintf fs "@\n@[<2>| %s@]@." msg ;
       Failure msg )