lisp-data-mode usage causing issues on Emacs 27

[bbatsov]

Hey there!

We've observed a CI failure in CIDER - https://app.circleci.com/jobs/github/clojure-emacs/cider/17136

From that trace it seems it's caused by Transient using lisp-data-mode:

[00:08.255]  [9/9] Installing package `transient' (0.8.5) from `gnu'...
[00:08.256]  File `https://elpa.gnu.org/packages/transient-0.8.5.tar' is not cached, retrieving...
[00:08.488]  File `https://elpa.gnu.org/packages/transient-0.8.5.tar.sig' is not cached, retrieving...
[00:08.897]  Debugger entered--Lisp error: (error "transient-pkg.el:0:0: error: void-function: (lisp-data-mode)")
               signal(error ("transient-pkg.el:0:0: error: void-function: (lisp-data-mode)"))
               error("%s:0:0: error: %s: %s" "transient-pkg.el" void-function (lisp-data-mode))
               autoload-generate-file-autoloads("transient-pkg.el" nil "/root/project/.eldev/27.2/packages/transient-0.8.5/transient-autoloads.el")
               update-directory-autoloads("/root/project/.eldev/27.2/packages/transient-0.8.5")
               package-generate-autoloads(transient "/root/project/.eldev/27.2/packages/transient-0.8.5")
               package--make-autoloads-and-stuff(#s(package-desc :name transient :version (0 8 5) :summary "Transient commands" :reqs ((emacs (26 1)) (compat (30 0 0 0)) (seq (2 24))) :kind tar :archive "gnu" :dir nil :extras ((:url . "https://github.com/magit/transient") (:keywords "extensions") (:maintainer "Jonas Bernoulli" . "[email protected]") (:authors ("Jonas Bernoulli" . "[email protected]")) (:commit . "b51a52a9c7a6562c19d03de4ce30b9c071bca8d2")) :signed nil) "/root/project/.eldev/27.2/packages/transient-0.8.5")

Oddly, the CI passes for Emacs 28, even if this got introduced in Emacs 29. I'm assuming it's some bug with compat.el, but I guess you'd know better.

[tarsius]

The *-pkg.el files get generated by the tools used to build packages for an *elpa. elpa-admin.el for [Non]GNU Elpa and package-build.el for Melpa. For one day back in 2024, the latter added -*- mode: lisp-data -*- to *-pkg.el files. If that's the issue, then zap your caches. If the former does it now, that's something you have to discuss with Stefan Monnier.

[bbatsov]

Hmm, there are no ELPA caches retained between the builds, so I'm a bit puzzled now. But to be clear - you haven't recently changed anything that might be related to this?

[tarsius]

I haven't changed anything in transient and I think it is a coincident that the issue shows up for this package. The relevant package-build commits are melpa/package-build@7df0854 and melpa/package-build@dd32541 from five months ago.

It looks like you might be trying to generate autoloads for *-pkg.el. Those metadata files don't contain anything that should be autoloaded.