bug#59956: 29.0.60: Failure when completing arguments in Eshell after variable interpolation

[Augusto Stoffel <arstoffel@gmail.com>]

On Sun, 18 Dec 2022 at 19:54, Stefan Monnier wrote:

> There's a tension here: we want the completion to operate on the actual
> buffer text obviously, so in some places we definitely want to see the
> "unexpanded argument" [1], but when it comes to looking at other arguments
> to decide which completion table to use at point, it's often more useful
> to see the expanded arguments (i.e. the thing that the command will
> actually see).  E.g. if the previous arg is `$foo` which expands to `-u`
> we'd probably prefer to see `-u` in order to know we should complete
> against user names.

If $foo is "-u -v"`, your patch will make pcomplete see this as a single
argument, no?

I think it makes sense to send the string "$foo" with the list '("-u"
"-v") embedded as text property, and add some convenience functions to
fetch the list for the pcomplete functions that can handle the more
refined information.