bug#43086: [PATCH] Allow tags backend to not query for TAGS file

[Dmitry Gutov <dgutov@yandex.ru>]

On 07/09/2024 09:18, Eli Zaretskii wrote:

>> Maybe just like this? This makes Xref identifier completion not query
>> for TAGS unless already loaded. In many cases that would be TRT,
>> although `C-u M-.` seems to regress (seems like we *would* want to query
>> eagerly there).
> 
> I don't understand why the obvious way of asking the user whether they
> would like to generate the tags table is not the solution here.  What
> did I miss?

I don't know if it's obvious, given that the optimal scenario at the 
beginning of the report describes

   ... allow the backend to never query a TAGS file

Adding a query to avoid querying might not be ideal. And if we did 
query, that would raise a question of where to store the answer (should 
it be global, or per-project, or temporary somehow?).

As it is, we already have a hint of the user preference from the fact 
that they have visited a TAGS file already (or not), or enabled 
etags-regen-mode (or not). It's not ironclad, but we could rely on these 
indicators to decide.