[Libguestfs] [PATCH] builder: read all the available notes from the index

[Pino Toscano]

On Wednesday 22 January 2014 22:51:02 Richard W.M. Jones wrote:
> On Wed, Jan 22, 2014 at 11:22:47PM +0100, Pino Toscano wrote:
> > Switch the internal storage for the notes of each entry to a sorted
> > list with all the subkeys available (which should represent the
> > translations to various languages).
> > The current outputs are the same (i.e. still the untranslated
> > notes), so this is just internal refactoring/preparation.
> > ---
> > 
> >  builder/builder.ml       |  4 ++--
> >  builder/index_parser.ml  | 19 +++++++++++++++----
> >  builder/index_parser.mli |  2 +-
> >  builder/list_entries.ml  | 10 +++++++---
> >  4 files changed, 25 insertions(+), 10 deletions(-)
> > 
> > diff --git a/builder/builder.ml b/builder/builder.ml
> > index bb0b108..19d1e42 100644
> > --- a/builder/builder.ml
> > +++ b/builder/builder.ml
> > @@ -200,9 +200,9 @@ let main () =
> > 
> >    (match mode with
> >    
> >    | `Notes ->                           (* --notes *)
> >    | 
> >      (match entry with
> > 
> > -    | { Index_parser.notes = Some notes } ->
> > +    | { Index_parser.notes = ("", notes) :: _ } ->
> > 
> >        print_endline notes;
> > 
> > -    | { Index_parser.notes = None } ->
> > +    | { Index_parser.notes = _ } ->
> 
> If you have to match on _, especially:
> > --- a/builder/list_entries.ml
> > +++ b/builder/list_entries.ml
> > @@ -71,10 +71,10 @@ and list_entries_long ~sources index =
> > 
> >            printf "%-24s %s\n" (s_"Download size:") (human_size
> >            size);
> >          
> >          );
> >          (match notes with
> > 
> > -        | None -> ()
> > -        | Some notes ->
> > +        | ("", notes) :: _ ->
> > 
> >            printf "\n";
> >            printf (f_"Notes:\n\n%s\n") notes
> > 
> > +        | _ -> ()
> 
> then you've done something wrong.  The problem is that the _ stops the
> compiler from finding missing cases in your code, since _ matches any
> case.  It's a bit like why it's bad practice to catch any exception
> in Java.

Yes, I know that.

> Since the list is going to contain something like one of these:
> 
>   [ "", "some notes" ]
>   [ "en", "some notes"; "ru", "..." ]
>   [ "ru", "..."; "", "..." ]
>   []
> 
> the pattern
> 
>   | ("", notes) :: _ ->
> 
> is only going to match the first of those, not the second or third.

If you notice the notes reading, I'm sorting the list by "language", so 
the empty string (= no translation) should always be the first, if 
present. So your lists above would actually be:

  [ "", "some notes" ]
  [ "en", "some notes"; "ru", "..." ]
  [ "", "..."; "ru", "..." ]
  []

I did that to just refactor without actually changing the behaviour, 
that is show the untranslated notes, thus also printing nothing if there 
are notes[..]= entries but no notes= one.
Other than that, sorting the list will help later when printing all the 
translated notes to JSON.

> Later when you actually implement language support you're going to
> 
> have to use List.assoc, so:
>   | notes when List.mem_assoc "en" notes ->
> 
>      printf "notes = %s" (List.assoc "en" notes)
> 
>   | [] ->
> 
>      printf "no notes"
> 
> (or something cleverer to deal with the current locale).

Yes, that's my step following this one, i.e. print the right language 
for the current locale when the output is internationalised, and all the 
languages in the JSON output.

-- 
Pino Toscano