| Message ID | ccbe07b719e498438a8f610cffa9ba274f6d608d.1632059166.git.public@yoctocell.xyz |
|---|---|
| State | New |
| Headers | show |
| Series | [bug#50614,core-updates,v2] build: utils: Add ‘list-when’ macro. | expand |
| Context | Check | Description |
|---|---|---|
| cbaines/applying patch | fail | View Laminar job |
| cbaines/issue | success | View issue |
Xinglu Chen schreef op zo 19-09-2021 om 15:50 [+0200]: > * guix/build/utils.scm (list-when): New syntax > * tests/build-utils.scm ("list-when: expr1 is non-#f", list-when: expr1 is #f"): > Test it. > * guix.texi (Build Utilities): Document it. > * .dir-locals.el: Set ‘scheme-indent-function’ to 1 for ‘list-when’. > --- If you will be doing this in (guix build utils), leading to a world-rebuild, you light want to define list-unless as well. E.g., 'boost' has (native-inputs `(("perl" ,perl) ,@(if (%current-target-system) '() `(("python" ,python-wrapper))) ("tcsh" ,tcsh))) with 'list-when', this could be rewritten to (native-inputs `(("perl" ,perl) ,@(list-when (not (%current-target-system)) `("python" ,python-wrapper)) ("tcsh" ,tcsh))) but '(when (not ...) EXP ...)' is simply '(unless EXP ...)', so it would be nice to be able to do (native-inputs `(("perl" ,perl) ,@(list-unless (%current-target-system) `("python" ,python-wrapper)) ("tcsh" ,tcsh))) Greetings, Maxime.
Hi, On Sun, 19 Sep 2021 at 15:50, Xinglu Chen <public@yoctocell.xyz> wrote: > +@lisp > +(if @var{test} > + (list @var{consequent} @dots{}) > + '()) > +@end lisp [...] > +@lisp > +(arguments > + `(#:configure-flags (list "--localstatedir=/var" > + "--sysconfdir=/etc" > + ,@@(list-when (hurd-target?) "--with-courage")))) > +@end lisp Personally, I am not convinced it helps the readibility. But that’s a matter of taste. :-) My concern is about the coherence. First, ’list-unless’ is also required by a similar pattern, see for instance: --8<---------------cut here---------------start------------->8--- gnu/packages/guile.scm:162: ,@(if (target-mingw?) '() `(("bash" ,bash-minimal))))) --8<---------------cut here---------------end--------------->8--- And second, these 2 patterns ’list-when’ and ’list-unless’ are used in by many files, see guix/build-system, guix/import, guix/describe, gnu/packages, gnu/system, gnu/services files. For the oneline pattern: “ag --scheme '@\(if' | grep '()'”. All should be replaced; which implies a world-rebuild I guess. Well, all in all, I am not convinced that all this work is worth for a small debatable readibility improvement. :-) All the best, simon
diff --git a/.dir-locals.el b/.dir-locals.el index 919ed1d1c4..554044ee8c 100644 --- a/.dir-locals.el +++ b/.dir-locals.el @@ -56,6 +56,7 @@ ((nil (eval . (put 'lambda* 'scheme-indent-function 1)) (eval . (put 'substitute* 'scheme-indent-function 1)) (eval . (put 'match-record 'scheme-indent-function 2)) + (eval . (put 'list-when 'scheme-indent-function 1)) ;; 'modify-inputs' and its keywords. (eval . (put 'modify-inputs 'scheme-indent-function 1)) diff --git a/doc/guix.texi b/doc/guix.texi index 9a3e8ae12c..4bea366b8e 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -8801,6 +8801,40 @@ `("PATH" ":" prefix ,(list coreutils)))))) @end lisp +@subsection Miscellaneous + +@cindex miscellaneous build utilities +This section documents some miscellaneous utilities. + +@deffn {Scheme Syntax} list-when @var{test} @var{consequent} @dots{} +Like @code{when} (@pxref{Conditionals,,, guile, GNU Guile Reference +Manual}), but if @var{test} evaluates to true, return @code{(list +@var{consequent} @dots{})}, and if @var{test} evaluates to false, return +the empty list. This replaces the following idiom: +@end deffn + +@lisp +(if @var{test} + (list @var{consequent} @dots{}) + '()) +@end lisp + +with this: + +@lisp +(list-when @var{test} @var{consequent} @dots{}) +@end lisp + +It can be useful when certain targets require additional configure +flags, e.g., + +@lisp +(arguments + `(#:configure-flags (list "--localstatedir=/var" + "--sysconfdir=/etc" + ,@@(list-when (hurd-target?) "--with-courage")))) +@end lisp + @subsection Build Phases @cindex build phases diff --git a/guix/build/utils.scm b/guix/build/utils.scm index 3beb7da67a..d3fb207ee5 100644 --- a/guix/build/utils.scm +++ b/guix/build/utils.scm @@ -8,6 +8,7 @@ ;;; Copyright © 2020 Efraim Flashner <efraim@flashner.co.il> ;;; Copyright © 2020, 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com> ;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be> +;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz> ;;; ;;; This file is part of GNU Guix. ;;; @@ -123,7 +124,9 @@ (define-module (guix build utils) make-desktop-entry-file - locale-category->string)) + locale-category->string + + list-when)) ;;; @@ -1613,6 +1616,18 @@ (define (locale-category->string category) LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE LC_TIME))) + +;;; +;;; Misc. +;;; + +;; If EXPR1 evaluates to a non-#f value, return '(EXPR2 ...). Otherwise, +;; return an empty list. +(define-syntax list-when + (syntax-rules () + ((_ expr1 expr2 ...) + (if expr1 (list expr2 ...) '())))) + ;;; Local Variables: ;;; eval: (put 'call-with-output-file/atomic 'scheme-indent-function 1) ;;; eval: (put 'call-with-ascii-input-file 'scheme-indent-function 1) diff --git a/tests/build-utils.scm b/tests/build-utils.scm index 6b131c0af8..b558feb47d 100644 --- a/tests/build-utils.scm +++ b/tests/build-utils.scm @@ -3,6 +3,7 @@ ;;; Copyright © 2019 Ricardo Wurmus <rekado@elephly.net> ;;; Copyright © 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com> ;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be> +;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz> ;;; ;;; This file is part of GNU Guix. ;;; @@ -287,5 +288,12 @@ (define-module (test build-utils) ("guile/bin" . ,(dirname (which "guile")))) "guile")))) +(test-equal "list-when: expr1 is non-#f" + (list 3 'bar) + (list-when 'foo (+ 1 2) 'bar)) + +(test-equal "list-when: expr1 is #f" + '() + (list-when #f (+ 2 3) 'bar)) (test-end)
* guix/build/utils.scm (list-when): New syntax * tests/build-utils.scm ("list-when: expr1 is non-#f", list-when: expr1 is #f"): Test it. * guix.texi (Build Utilities): Document it. * .dir-locals.el: Set ‘scheme-indent-function’ to 1 for ‘list-when’. --- Changes since v1: * Add an entry for ‘list-when’ in .dir-locals.el. * Some fixes to the documentation. .dir-locals.el | 1 + doc/guix.texi | 34 ++++++++++++++++++++++++++++++++++ guix/build/utils.scm | 17 ++++++++++++++++- tests/build-utils.scm | 8 ++++++++ 4 files changed, 59 insertions(+), 1 deletion(-) base-commit: 22f7d4bce1e694b7ac38e62410d76a6d46d96c5d