Re: Combine multiple (straight-)use-package commands into one.

[Omar Polo <op@omarpolo.com>]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

> On Sat, Jun 12, 2021 at 5:57 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>>
>> On Ubuntu 20.04, according to the instruction
>> [here](https://github.com/raxod502/straight.el/issues/786#issuecomment-859155336),
>> I use the following settings in my Emacs init file:
>>
>> ```
>> ;;Bootstrap straight
>> (defvar bootstrap-version)
>> (let ((bootstrap-file
>>        (expand-file-name "straight/repos/straight.el/bootstrap.el"
>> user-emacs-directory))
>>       (bootstrap-version 5))
>>   (unless (file-exists-p bootstrap-file)
>>     (with-current-buffer
>>         (url-retrieve-synchronously
>>          "https://raw.githubusercontent.com/raxod502/straight.el/develop/install.el"
>>          'silent 'inhibit-cookies)
>>       (goto-char (point-max))
>>       (eval-print-last-sexp)))
>>   (load bootstrap-file nil 'nomessage))
>>
>> ;; Install use-package via straight
>> (straight-use-package 'use-package)
>>
>> ;; Setting this to `t' makes it so that you don't need to include the :straight
>> ;; keyword in use-package declarations unless you want to add/extend the package
>> ;; installation recipe.
>>
>> (setq straight-use-package-by-default t) ; straight's equivalent of
>> `use-package-always-ensure'.
>> ```
>> Now, I want to install multiple package hosted in recipe repositories
>> (such as MELPA) as shown below with only one (straight-)use-package
>> command, is it possible?
>> ```
>> (use-package flycheck)
>> (use-package lsp-mode)
>> (use-package dash)
>> (use-package posframe)
>> (use-package s)
>> (use-package ein)
>> (use-package smartparens)
>> (use-package valign)
>> (use-package multi-term)
>> ```
>
> Based on the code snippets at
> <https://github.com/flakyhermit/emacs.d/blob/6b488895071e980433facf648f482974526d6a13/init.el#L22>,
> I figured out the following solution with `straight-use-package'
> command:
>
> (defvar package-list)
> (setq package-list '(
>        flycheck lsp-mode dash posframe
>        s ein smartparens valign
>        multi-term
> ))
>
> (mapc (lambda(package-name)
> (straight-use-package package-name)) package-list)
>
> But I still don't know the corresponding implementation with
> `use-package' command.

C-h f use-package RET says that

> use-package is a Lisp macro in ‘use-package-core.el’.

being a macro and not a function[0], it means that it follows different
rule for the evaluation.  (use-package foo ...) is something that gets
*expanded* at *compile time* in some other lisp code, it's not something
you can pass to mapc.  You need to expand the loop *at compile* time to
load multiple packages, something like the following (untested)

--------8<--------
(defmacro use-multiple-packages (&rest packages)
  `(progn
    ,@(mapcar (lambda (p) `(use-package ,p))
              packages)))

(use-multiple-pacakges foo
                       bar
		       baz
		       ...)
-------->8--------

but it becomes not useful, since the main point of use-package is IMHO
the syntax sugar for adding hooks, bindings etc.  If you don't care
about that stuff, a simple loop over package-install/package-installed-p
is probably enough.

> Regards

[0]: see (info "(elisp)macros") for more information about how elisp
     macros works.