Re: [PATCH v2] ref-filter.c: pass empty-string as NULL to atom parsers

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Oct 2, 2017, 22:40 UTC
Message-ID: <20171002224052.GR19555@aiede.mtv.corp.google.com>
In-Reply-To: <20171002161034.44867-1-me@ttaylorr.com>

Hi,

Taylor Blau wrote:

Show 17 quoted lines

> Peff points out that different atom parsers handle the empty
> "sub-argument" list differently. An example of this is the format
> "%(refname:)".
>
> Since callers often use `string_list_split` (which splits the empty
> string with any delimiter as a 1-ary string_list containing the empty
> string), this makes handling empty sub-argument strings non-ergonomic.
>
> Let's fix this by assuming that atom parser implementations don't care
> about distinguishing between the empty string "%(refname:)" and no
> sub-arguments "%(refname)".
>
> Signed-off-by: Taylor Blau <me@ttaylorr.com>
> ---
>  ref-filter.c            | 10 +++++++++-
>  t/t6300-for-each-ref.sh |  1 +
>  2 files changed, 10 insertions(+), 1 deletion(-)

The above does a nice job of explaining

 - what this change is going to do
 - how it's good for the internal code structure / maintainability

What it doesn't tell me about is why the user-facing effect won't cause problems. Is there no atom where %(atom:) was previously accepted and did something meaningful that this may break?

Looking at the manpage and code, I don't see any, so for what it's worth, this is

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>

but for next time, please remember to discuss regression risk in the commit message, too.

Thanks, Jonathan