[sledge] Protect Trace.parse from invalid user input

Summary:
Trace.parse is exposed across a module boundary, so handle its own
exceptions and return an `error`.

Reviewed By: mbouaziz

Differential Revision: D14081602

fbshipit-source-id: 4087c5d5b

sledge/src/config.ml

@@ -9,8 +9,9 @@
 
 let trace_conv =
   let parse s =
-    try Ok (Trace.parse s).trace_mods_funs with _ ->
-      Error (`Msg ("Invalid trace spec: " ^ s))
+    match Trace.parse s with
+    | Ok c -> Ok c.trace_mods_funs
+    | Error err -> Error err
   in
   let print fs c =
     let pf fmt = Format.fprintf fs fmt in

sledge/src/trace/trace.ml

@@ -24,6 +24,7 @@ let all = {none with trace_all= true}
 let config : config ref = ref none
 
 let parse s =
+  try
     let default = Map.empty (module String) in
     let index_from s i =
       Option.merge ~f:min
@@ -64,13 +65,14 @@ let parse s =
               Map.set m ~key:mod_name
                 ~data:
                   { trace_mod
-                ; trace_funs= Map.set trace_funs ~key:fun_name ~data:enabled
-                }
+                  ; trace_funs=
+                      Map.set trace_funs ~key:fun_name ~data:enabled }
           | mod_name, None, enabled ->
               Map.set m ~key:mod_name
                 ~data:{trace_mod= Some enabled; trace_funs= default} )
     in
-  {none with trace_mods_funs}
+    Ok {none with trace_mods_funs}
+  with Assert_failure _ -> Error (`Msg ("Invalid trace spec: " ^ s))
 
 let init ?(margin = 300) ~config:c () =
   Format.set_margin margin ;

sledge/src/trace/trace.mli

@@ -23,7 +23,7 @@ type config =
 
 val none : config
 val all : config
-val parse : string -> config
+val parse : string -> (config, [> `Msg of string]) result
 
 val init : ?margin:int -> config:config -> unit -> unit
 (** Initialize the configuration of debug tracing. *)