bug#54459: 29.0.50; Simplify connection-local variables (feature request)

[Michael Albinus <michael.albinus@gmx.de>]

Ergus <spacibba@aol.com> writes:

Hi,

> Suppose:
>
> C-x C-f /ssh:myhost:file1
> C-x C-f /ssh:myhost:file2
> (executable-find mycommand 1)
> And here we set the connection local variable...
>
> When we go to file1 if does not know about the variable in spite of it
> is in the same host.

I recommend to move the code setting connection-local variables in a
funcion called by a hook, which is applied when visiting files in your
use case.

>>--8<---------------cut here---------------start------------->8---
>>(connection-local-set-profile-variables
>> 'profile
>> (append
>>  (connection-local-get-profile-variables 'profile)
>>  my-variables-list))
>>--8<---------------cut here---------------end--------------->8---
>>
> Could you consider to add a snippet in the documentation explaining
> this? Please?

Done in the Elisp manual, pushed to master as commit aec44a5be3.

>>That's hard to do. A user could change the remote PATH while the result
>>of executable-find is cached. Furthermore, Tramp appends the local part
>> of the remote default-directory to the directory search list.
>
> SO this means that the executable in default-directory are also
> considered? Like on Windows? I was not aware of that...

Well, this is rather an implementation detail, not documented. And I'm
not sure it is the best decision, we just needed a last element in
exec-path which is comparable to the last element in the local case of
exec-path.

>>You could write your own function, using Tramp's cache mechanism, but at
>>your own risk. Something like (untested)
>>
>>--8<---------------cut here---------------start------------->8---
>>(defun my-executable-find (command &optional remote)
>>  (if (and remote (file-remote-p default-directory))
>>      (with-tramp-connection-property
>>	  (tramp-get-process (tramp-dissect-file-name default-directory))
>>	  (concat "executable-find-" command)
>>	(executable-find command remote))
>>    (executable-find command remote)))
>>--8<---------------cut here---------------end--------------->8---
>>
> I was thinking in something like:
>
> (executable-find command &optional remote cache) but basically the same idea.

This cannot be generalized, the code uses Tramp specific functions. A
remote file name does not always mean invoking Tramp ...

> Thanks,
> Ergus

Best regards, Michael.