Re: [Libguestfs] [PATCH 2/2] OCaml tools: add output selection for --machine-readable
On Tue, Aug 21, 2018 at 05:44:30PM +0200, Pino Toscano wrote:
+let machine_readable_printf fs =
+ let get_machine_readable_channel () =
+ let open_machine_readable_channel () =
+ match !machine_readable_output with
+ | NoOutput ->
+ (* Trying to use machine_readable_printf when --machine-readable was
+ * not enabled, and thus machine_readable () returns false.
+ *)
+ failwith "internal error: machine_readable_printf used with no
--machine-readable"
I wonder if there's a way to avoid this error at compile time.
Replace the ‘machine_readable ()’ function that returns boolean with
one which returns an optional printf function. Then caller code would
do:
match machine_readable () with
| None -> () (* ie. not --machine-readable *)
| Some pr ->
pr "stuff\n";
exit 0
Of course the devil will be in the details as to whether this actually
works with our existing callers.
+ fprintf (get_machine_readable_channel ()) fs
I'm surprised this works and you didn't need to use ksprintf.
(* No elements and machine-readable mode? Print some facts. *)
if elements = [] && machine_readable () then (
- printf "virt-dib\n";
+ machine_readable_printf "virt-dib\n";
let formats_list = Output_format.list_formats () in
- List.iter (printf "output:%s\n") formats_list;
+ List.iter (machine_readable_printf "output:%s\n") formats_list;
exit 0
);
So this caller would become:
match machine_readable (), elements = [] with
| None, _ -> ()
| Some pr, [] ->
(* existing code, replacing printf with pr *)
| Some _, _ ->
(* this is a new case giving an error when the user
uses --machine-readable + a list of elements, which I believe
is not caught in the current code *)
error (f_"--machine-readable cannot be used with elements on the command
line")
Rich.
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