From: Stefan Monnier <monnier@iro.umontreal.ca>
To: emacs-devel@gnu.org
Subject: Re: emacs-26: `with-eval-after-load' docstring omission
Date: Wed, 28 Feb 2018 18:22:22 -0500 [thread overview]
Message-ID: <jwv606gk8ro.fsf-monnier+gmane.emacs.devel@gnu.org> (raw)
In-Reply-To: 4e07d7b4-f1f7-0d5d-5f2a-b5e491ab4303@gmail.com
> Is that because macroexpansion happens eagerly in the body of the defun, too?
More or less. It's because it *can* happen eagerly (it also does
nowadays in many cases, but the exact time when macroexpansion takes
place is not specified precisely and it can&does vary depending on
circumstances and Emacs version).
> I guess I just don't expect that to happen unless the file is
> byte-compiled, really :/
Whether the code is byte-compiled or not is an implementation detail
which could change. Any code which depends on whether it gets compiled
is considered as buggy in my book.
>> In your case, you do want the quote because you need to delay
>> macro-expansion, but I think it's cleaner to solve this problem by
>> *explicitly* using a quote, rather than by relying on the messy
>> semantics of the macro/function you happen to be using.
> I'm not sure I follow: doesn't the compiler macro mean that even explicitly
> using a quote isn't enough?
In that one specific case, yes, but in general using a quote is sufficient.
You should not use `eval-after-load` nowadays, you should only use
`with-eval-after-load`, so you'd write something like
(with-eval-after-load 'flycheck
;; Use eval+quote to delay macro expansion.
(eval '(flycheck-define-command ...)))
>> E.g. your exact same problem could show up if you used, say,
>> (add-hook 'flycheck-mode-hook ...)
>> instead of
>> (with-eval-after-load ...)
>> but you wouldn't ask for a change in add-hook to "solve" your problem.
>
> Would the problem there be that the body of the lambda I'd pass to add-hook
> would be eagerly macro-expanded?
At least could, yes.
> I think the big difference between these two is that I expect
> `with-eval-after-load` to really behave differently, and the reason for
> expecting that is that we don't otherwise have a convenient way to delay
> macroexpansion and execution of a form until a file is loaded, right?
> Maybe we need a `with-macroexp-and-eval-after-load`?
What I'm trying to say is that delaying macroexpansion is something
that's needed in many more cases than in conjunction to
`eval-after-load` so any solution specifically linked to
`eval-after-load` is just an ad-hoc hack.
Stefan
next prev parent reply other threads:[~2018-02-28 23:22 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-23 13:42 emacs-26: `with-eval-after-load' docstring omission Vicente Vera
2018-02-23 14:16 ` Noam Postavsky
2018-02-24 14:42 ` Vicente Vera
2018-02-27 20:40 ` Clément Pit-Claudel
2018-02-27 20:58 ` Stefan Monnier
2018-02-28 14:53 ` Clément Pit-Claudel
2018-02-28 23:22 ` Stefan Monnier [this message]
2018-03-17 6:01 ` Clément Pit-Claudel
2018-03-17 14:19 ` Stefan Monnier
2018-04-13 16:00 ` Clément Pit-Claudel
2018-04-13 18:02 ` Stefan Monnier
2018-04-13 18:28 ` Clément Pit-Claudel
2018-04-13 18:41 ` Stefan Monnier
2018-04-13 22:43 ` Stefan Monnier
2018-02-27 20:21 ` Stefan Monnier
2018-03-03 15:06 ` Vicente Vera
2018-03-03 15:38 ` Clément Pit-Claudel
2018-03-03 21:52 ` Stefan Monnier
2018-03-04 16:04 ` Vicente Vera
2018-03-05 3:39 ` Stefan Monnier
2018-03-09 1:00 ` Noam Postavsky
2018-03-09 4:55 ` Stefan Monnier
2018-03-09 0:47 ` Vicente Vera
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