Re: Generation of tags for the current project on the fly

[Dmitry Gutov <dgutov@yandex.ru>]

On 1/18/18 02:20, Tom Tromey wrote:

> Dmitry> ctags supports incremental updates?
> 
> Yeah, see "-u" in "ctags --help":

Cool. This is probably from Universal Ctags. Still not in Ubuntu (17.04, 
at least).

> -u, --update
>          Update the tag entries for the given files, leaving tag
>          entries for other files in place.  Currently, this is
>          implemented by deleting the existing entries for the given
>          files and then rewriting the new entries at the end of the
>          tags file.  It is often faster to simply rebuild the entire
>          tag file than to use this.

Seems like it updates the file in place. And your implementation copies 
the entries and allocates a new file. Any difference in performance that 
you noticed?

> Dmitry> The config file duplicates some info in .gitignore and
> Dmitry> project-vc-ignores, though. Which is unfortunate.
> 
> True, but there are two reasons for this.  One, there are still several
> version control systems in use, and I didn't want to try to parse every
> config file.

I think it should work like:

git ls-files | etags -

Replace 'git ls-files' with an appropriate incantation for each VCS.

> Second, sometimes a generated file will be checked in, but
> you might still want to omit it from TAGS -- so some mechanism like this
> is needed.

Yup. This seems to work (excluding .clang_format; there's also an option 
to read additional ignores from a file):

git ls-files -cdmo --exclude-standard -x .clang-format | etags -

> Dmitry> I also doubt that 'make tags' will go away anytime soon.
> 
> Sure, me too, but this approach is taken by more tools nowadays, and it
> can live alongside "make tags".

Is that true? The modern tools have taken the approach of duplicating 
the ignore lists?

> Dmitry> Any chance your code supports something analogous to 'global
> Dmitry> --single-update' (except with multiple file arguments, hopefully)?
> Dmitry> That's what I've been trying to describe.
> 
> It could certainly be done without much effort.

Very good. Does it handle file deletions as well?

>>> I suppose I could push my branch to git if that would be convenient.
>>> Just let me know.
> 
> Dmitry> I'm sure it would be helpful, even if only to study the approach.
> 
> I pushed it to feature/etags-update.

Thanks! I'll do some benchmarking if nobody beats me to it.