bug#41423: Installing the fix for bug#41423 on emacs-27 (was: 27.0.91; eshell file completion in tramp dir is slow (3 minutes) [regression on pretest])

[Stefan Monnier]

Stefan Monnier [2021-01-31 21:45:39] wrote:
> FWIW, I installed a variant of my earlier patch into `master`.
> I suspect it has a few rough edges, so watch out for regressions, please
> and complain to me (with as precise a recipe as you can) when you bump
> into them,

I installed a further change which should fix the main issue I could
foresee.  I'm now reasonably happy with the patch (I think it's "right"
rather than a quick ad-hoc fix.  It deserves further improvements to add
some form of caching, but that's largely orthogonal to this bug report).

IIUC Michael had marked this bug as "blocking" for Emacs-27, so this
argues for installing it on the `emacs-27` branch.

The patch is not without risks seeing how it changes a function from
returning a list to returning a function and how it fundamentally
changes *when* the code is executed.  So I'm not sure whether it should
go on the `emacs-27` branch:

A- For non-Eshell users it is "obviously safe".
B- For Eshell-over-Tramp users it should be a clear improvement even if
   it turns out to introduce some unforeseen regressions in some cases.
C- Finally, Eshell-not-over-Tramp users should hopefully see no
   difference at all, which mostly means no improvement to make up for
   any risk of regression.

So, is the improvement in B worth the risk in C?


        Stefan