Package-Requires header can span multiple lines

[tarsius]

In magit.el I use this, for example:

;; Package-Requires: (
;;     (emacs "27.1")
;;     (compat "30.0.1.0")
;;     (dash "2.19.1")
;;     (magit-section "4.2.0")
;;     (seq "2.24")
;;     (transient "0.8.2")
;;     (with-editor "3.4.3"))

(The trick is to put the open parenthesis on the same line as the keyword.)

With package-lint that results in:

magit.el:21:0: error: Couldn't parse "Package-Requires" header: \
  End of file during parsing

[purcell]

Does that also work in older Emacsen, e.g. back to 24?

[purcell]

ie. is it valid syntax for package.el, lm-maint etc in those older versions?

[tarsius]

This was added in e8c46c2b6f76cc055366041b6112d61dd5f2dcf4, see https://debbugs.gnu.org/cgi/bugreport.cgi?bug=36301. So the first Emacs release to support it is 27.1.

Recently (bb5399e3cd75450db6db9b3c5829f7bd87ca1308, upcoming 30.1) this was moved to a new lm-package-requires function.

If a package specifies that it needs at least 27 or later, then multi-line Package-Requires, should not result in a linting warning. If it uses a multi-line value but does not also specify that 27.1 or later is required, then that should result in a warning.

[purcell]

If a package specifies that it needs at least 27 or later, then multi-line Package-Requires, should not result in a linting warning. If it uses a multi-line value but does not also specify that 27.1 or later is required, then that should result in a warning.

I don't really agree — you can't guarantee that package headers won't be parsed by older Emacsen, and in those versions you want Emacs to say, "Emacs 27 is not installable", not "Malformed header". This is why we have a lint warning (error, even?) about Package-Requires entries that don't have versions, e.g. (seq).

[tarsius]

It's not guaranteed that this won't happen, but it is fairly unlikely. Nowadays, Melpa (and [Non]GNU Elpa) generate a *-pkg.el file and distribute a tarball, even for packages that consist of nothing but a single library. package.el will then only look at that file and ignore the library headers.

Old package-install-file and package-install-from-buffer would fail though.

It's up to you of course, but I think this should downgraded to a warning.

(This would be a non-issue if they started distributing new releases of package.el on GNU Elpa. I suggested that on emacs-devel before, but the response didn't make me hopeful.)