bug#59214: [PATCH] Alternate rust-analyzer command added

[Eli Zaretskii]

> Date: Thu, 17 Nov 2022 18:11:32 +0000
> From: "M. Ian Graham" <hello+emacs@miangraham.com>
> Cc: 59214@debbugs.gnu.org, Eli Zaretskii <eliz@gnu.org>, João Távora 
> <joaotavora@gmail.com>
> 
> Pankaj Jangid <pankaj@codeisgreat.org> wrote:
> 
> > -(defvar eglot-server-programs `((rust-mode . ,(eglot-alternatives 
> > '("rust-analyzer" "rls")))
> > +(defvar eglot-server-programs `((rust-mode . ,(eglot-alternatives 
> > '("rust-analyzer" "("rustup" "run" "stable" "rust-analyzer") "rls")))
> 
> I just noticed this quote from the announcement at 
> https://blog.rust-lang.org/2022/09/22/Rust-1.64.0.html#rust-analyzer-is-now-available-via-rustup
>  :
> 
> > At this time, to run the rustup-installed version, you need to invoke it 
> > this way:
> > rustup run stable rust-analyzer
> > The next release of rustup will provide a built-in proxy so that running 
> > the executable rust-analyzer will launch the appropriate version.
> 
> So the current situation is temporary. A rustup-side fix is coming. Once it 
> arrives, the right answer--even for rustup users--will be "just add what you 
> want to PATH and eglot will defer to your environment." Rustup will do this 
> for them automatically, for the rust version of their preference, and eglot 
> will just work.
> 
> In the meantime, as is, rustup users have the option of symlinking 
> rust-analyzer into .cargo/bin or adding its location directly to PATH. Anyone 
> not comfortable doing this is also probably not running emacs from master, so 
> they're unlikely to benefit from a short-term elisp fix until the problem 
> goes away. And if emacs adds code depending on rustup, subsequently removing 
> what should theoretically be a temporary fix will in practice break users 
> remaining on older rustup versions.
> 
> Unless I'm misunderstanding the situation above or something has changed 
> since the announcement, to me it seems prudent to wait on rustup's fix and 
> avoid letting emacs develop an opinion about the installation method or 
> version details of external components.

FWIW, I think Rust is too crazy for us to follow its daily changes and
offer support for its server OOTB in eglot-server-programs.  Emacs is
not equipped to follow such frequent and radical changes.  If we want
to make this seamless for users of Rust, we should provide a special
command to update eglot-server-programs with whatever it is the latest
Rust fashion.  Or maybe we should even leave that to Rust mode.