Re: [PATCH v1 3/5] list-objects-filter: implement composite filters

[Jeff King <peff@peff.net>]

On Tue, Jun 04, 2019 at 10:19:52AM -0700, Matthew DeVore wrote:

> On Tue, Jun 04, 2019 at 12:13:32PM -0400, Jeff King wrote:
> > > -	return has_reserved_character(subspec, errbuf) ||
> > > -		url_decode(subspec, errbuf) ||
> > > -		gently_parse_list_objects_filter(
> > > -			&filter_options->sub[new_index], subspec->buf, errbuf);
> > > +	decoded = url_percent_decode(subspec->buf);
> > 
> > I think you can get rid of has_reserved_character() now, too.
> 
> The purpose of has_reserved_character is to allow for future
> extensibility if someone decides to implement a more sophisticated DSL
> and give meaning to these characters. That may be a long-shot, but it
> seems worth it.

I think you'll find that -Wunused-function complains, though, if nobody
is calling it. I wasn't sure if what you showed in the interdiff was
meant to be final (I had to add a few other variable declarations to
make it compile, too).

> > The reserved character list is still used on the encoding side. But I
> > think you could switch to strbuf_add_urlencode() there?
> 
> strbuf_addstr_urlencode will either escape or not escape all rfc3986
> reserved characters, and that set includes both : and +. The former
> should not require escaping since it's a common character in filter
> specs, and I would like the hand-encoded combine specs to be relatively
> easy to type and read. The + must be escaped since it is used as part of
> the combine:... syntax to delimit sub filters. So
> strbuf_addstr_url_encode would have to be more customizable to make it
> work for this context. I'd like to add a parameterizable should_escape
> predicate (iow function pointer) which strbuf_addstr_urlencode accepts.
> I actually think this will be more readable than the current strbuf API.

That makes some sense, and I agree that readability is a good goal. Do
we not need to be escaping colons in other URLs? Or are the strings
you're generating not true by-the-book URLs? I'm just wondering if we
could take this opportunity to improve the URLs we output elsewhere,
too.

-Peff