Nice error message when LSP not found in PATH

[unhammer]

I have (add-hook 'js-ts-mode-hook #'eglot-ensure) but I don't have typescript-language-server in my global PATH, so whenever I open a js file I see a Message like

Error in post-command-hook (#[0 "\303\301!\205�\0r\301q\210\304\305\300\242\306#\210
?\205�\0\307\310\311 \")\207" [(#0) #<buffer foo.js> eglot--managed-mode buffer-live-p remove-hook post-command-hook t apply eglot--connect eglot--guess-contact] 4]): (file-missing "Searching for program" "No such file or directory" "typescript-language-server")

which is kind of noisy and hard to read. It'd be nicer if eglot-ensure just said Language server typescript-language-server not found in PATH, eglot will be turned off or something friendler than that. In particular because this might be the first message someone sees after installing eglot for the first time and not having everything fully set up :-)

[joaotavora]

It would be nicer, but it would also be nicer if so many people using eglot-ensure would stop using it and just use M-x eglot.

So many Reddit recipes being copied around and eglot-ensure is specifically described like this in the manual:

The function eglot-ensure will start an Eglot session for each buffer in which foo-mode is turned on, if there isn’t already an Eglot session that handles the buffer. Note that this variant of starting an Eglot session is non-interactive, so it should be used only when you are confident that Eglot can be started reliably for any file which may be visited with the major-mode in question.

So if you are not confident of that, don't use it.

But I'll see what I can do. In the meantime, you can always define a my-eglot-ensure function wrapper which catches errors and demotes them to warnings.

In particular because this might be the first message someone sees after installing eglot for the first time and not having everything fully set up :-)

If they are brainless reddit copy-all-the-things newbies, I guess yes.

EDIT: Reddit users are not necessarily brainless, so I hereby apologize. But they use a platform where popular upvoted things, not scientifically tested things, bubble up and become truth. Great for spreading misleading ideas, fake news, etc. I happen not to like that, in software and so many other fields. I prefer the pre-post-truth world where our brains are more actively engaged in healthy scrutiny.

[unhammer]

There is a perfectly fine reason that people recommend eglot-ensure – it means that you don't have to manually M-x eglot for every single buffer of a project. I can't put eglot in a mode hook. I would like to have LSP support automatically turned on in projects where there is a language server set up, but at the same time not have to deal with warnings when I just open some random file where LSP isn't set up. I want it to be non-interactive.

(Btw, if you really want to recommend users against eglot-ensure, maybe warn about it in the docstring? Currently it just says
"Start Eglot session for current buffer if there isn't one.")

[joaotavora]

There is a perfectly fine reason that people recommend eglot-ensure – it means that you don't have to manually M-x eglot for every single buffer of a project

Yes, but no. Because that is not true. Just try it.

[unhammer]

Aha, I learn something new, thank you. So one M-x eglot per project is enough to get it going within that project; perhaps I got confused by trying it with files of different projects.

[joaotavora]

Good to have clarified that. I'll try that idea of demoting the error to warning so it shows up in the *Warnings* buffer, and follow your suggestion of more forcefully clarifying that eglot-ensure might not be a good idea (a common problem is trying to start Eglot up in an humongous or poorly setup project by accident and then complaining that "Eglot locks up my Emacs")

[joaotavora]

I changed eglot-ensure to demote errors to warnings. See https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=3ab99e977db01939cc42f285d5ce58807cf2e7d0

In that commit I also expanded the manual even more to clarify that one does NOT need to invoke M-x eglot for every buffer in a project.

[unhammer]

That was quick :) Just tried it, that looks much nicer: [eglot] (warning) Searching for program: No such file or directory, typescript-language-server :-)