eglot causes eldoc error: (invalid-function incf)

[dangom]

Trying eglot for the first time on a python file.
Everything works but I get on the minibuffer an eldoc error: (invalid-function incf).

For context: I use straight for package management, but have no declarations regarding eglot nor eldoc on my init.el.
Emacs 30.1, but I tried under 29.4 with the same issue.

If I set debug-on-error, I get the following, which isn't really informative:

Debugger entered--Lisp error: (invalid-function incf)
  incf(0)
  #f(compiled-function (method origin) #<bytecode -0xaadc1b6e8ed7d7>)(:patient eglot-signature-eldoc-function)
  eldoc--make-callback(:patient eglot-signature-eldoc-function)
  #f(compiled-function (f) #<bytecode -0x6cf6f9fa4609ff8>)(eglot-signature-eldoc-function)
  run-hook-wrapped(#f(compiled-function (f) #<bytecode -0x6cf6f9fa4609ff8>) eglot-signature-eldoc-function)
  eldoc-documentation-compose()
  eldoc--invoke-strategy(nil)
  eldoc-print-current-symbol-info()
  #f(compiled-function () #<bytecode -0x1617e223c153308b>)()
  apply(#f(compiled-function () #<bytecode -0x1617e223c153308b>) nil)
  timer-event-handler([t 0 0 500000 nil #f(compiled-function () #<bytecode -0x1617e223c153308b>) nil idle 0 nil])

Has anyone seen this before, or would have an idea how to go about debugging of fixing this?

Thank you.

[joaotavora]

Someone messed up and started calling incf in eldoc.el. Submit a bug to bug-gnu-emacs@gnu.org and put stefankangas@gmail.com in CC. call attention to the last lines of this blurb:

;;; eldoc.el --- Show function arglist or variable docstring in echo area  -*- lexical-binding:t; -*-

;; Copyright (C) 1996-2025 Free Software Foundation, Inc.

;; Author: Noah Friedman <friedman@splode.com>
;; Keywords: extensions
;; Created: 1995-10-06
;; Version: 1.15.0
;; Package-Requires: ((emacs "26.3"))

;; This is a GNU ELPA :core package.  Avoid functionality that is not
;; compatible with the version of Emacs recorded above.

[joaotavora]

But... if you weren't using straight, you wouldn't have this problem

[HyperSuperMetaCtrl]

May I ask how using straight is causing a problem here?

[joaotavora]

Straight grabs the bleeding edge from master, makes a package out of that, so effectively jumps over the safety of the release mechanism. Package.el doesn't do that (by default).

[dangom]

Thanks a ton. Indeed changing incf for cl-incf and decf for cl-decf on eldoc.el fixes the issue. I've submitted the report.

(also, thanks for eglot. It really does just work out of the box)

[HyperSuperMetaCtrl]

I also tried that. But building my own Emacs for this oneliner seemed a bit overkill to me even if it worked out fine.
I found out that adding (use-package eldoc :straight (:type built-in)) resolved that issue for me.

[joaotavora]

It only resolves the issue because you're using a fairly recent Emacs. If you do need to get a newer Eldoc, though not the bleeding edge one, it will fail.

[joaotavora]

also, thanks for eglot. It really does just work out of the box

Clearly only when the box is nothing but Emacs ;)

[HyperSuperMetaCtrl]

The issue was fixed. Thank you @dangom for reporting the bug on the mailing list.