[Gambas-user] New component gb.rss to generate and parse RSS documents

[Tobias Boege]

On Sun, 16 Apr 2017, Benoît Minisini wrote:
> Le 02/04/2017 à 18:07, Tobias Boege a écrit :
> >
> >   * The date conversion routines ignore timezones completely, because
> >     I have no clue about working with timezones in Gambas.
> >
> 
> Hi, Tobias.
> 
> I have added in revision #8122 two functions to the gb.util component:
> 
> Date.ToRFC822(), to convert a Gambas date/time value to its RFC822 
> string representation, with the timezone.
> 
> Date.FromRFC822(), to do the contrary.
> 
> Tell me if you can use them, and if you need me to add the same 
> functions for RFC3339 date format used by Atom.
> 

Thanks for these. Reading the code (not testing it yet), I noticed four
things:

  * The weekday and second parts in the format are optional in the RFC
    but mandatory in your parser.

  * The year is a 2-digit number in the RFC. The RSS spec says it prefers
    4 digits. My current parser in gb.web.feed supports both, but treats
    2-digit years XY as 19XY (which I think is the most sensible
    interpretation with respect to the RFC but sadly excludes publication
    dates for news items near Christ's birth).

  * There is no consistency check in the parser if, in case a weekday is
    given, it matches the weekday of the date, like

      Fri, 18 Apr 2017 12:00:00 GMT

    would be invalid by the RFC ("5.2 SEMANTICS"), because the 18 Apr 2017
    is a Tuesday.

  * At one point you use Format$(..., "hh:nn:ss") which I think may be
    dangerous, because Format$() (as per docs) replaces ":" by the locale-
    specific time separator. I don't know if there are locales where this
    is different from ":", but the RFC requires it to be ":" exactly.

My parser does these four things. If you want to add them, the gb.web.feed
code is sufficiently commented in the relevant places.

As for Atom, I don't have a definite plan for when I'll add these classes
(haven't even read the specs yet). I don't need the functions right now,
at least.

About the incorporation of timezones in gb.web.feed (the last thing before
I mark the component as "Unfinished but stable"), my plan is to replace the
Date variables in the Rss* classes by an RssDate compound, consisting of a
normalised Date and a Timezone string (or constant), with an "apply timezone"
method probably. If you have a better idea, please let me know.

Regards,
Tobi

-- 
"There's an old saying: Don't change anything... ever!" -- Mr. Monk