Re: Choosing tags tables

[Eli Zaretskii]

> From: Daniel Lopez <daniel.lopez999@gmail.com>
> Date: Thu, 20 Jul 2017 04:17:23 +0100
> 
> So I set it up so that for example in my c++-mode-hook it sets 
> tags-table-list with the multiple tags files I want to use for C++; the 
> first is the library I use in all my C++ projects and the second is the 
> project-specific tags file (assuming all project sources are in the same 
> directory as TAGS, for now). I'm setting it as buffer-local so that it 
> only applies to tag searches that are started when that buffer is current:
> 
>   (setq-local tags-table-list
>     (list "/home/daniel/docs/code/c/reusable/checkout/dan/TAGS"
>           (concat default-directory "TAGS")))
> 
> However when I then do a xref-find-definitions Emacs prompts me:
> "Visit tags table (default TAGS):"
> because (in visit-tags-table-buffer) it's not looking for the 
> buffer-local value of tags-table-list, only the global which is nil. If 
> I go along with it and enter something then Emacs sets tags-file-name to 
> my entry which means now I only have one tags file and my 
> tags-table-list gets ignored.

I think this should be reported as a bug, using report-emacs-bug.

In your report, please provide more details about your conclusion that
visit-tags-table-buffer ignores buffer-local values: AFAICT, that
function does have provisions for considering local values, so it
could be that xref-find-definitions fails to invoke some functions
correctly or with the right buffer being the current one.  A Lisp
backtrace at the time visit-tags-table-buffer could help.

Also, a minimal test case to reproduce the problem will be useful.

> Does anyone know of a better way to get this effect?

The way you tried first should "just work".