Message ID | b7ee7798dbf384021126a2cd4366b604730181b8.1631776133.git.public@yoctocell.xyz |
---|---|
State | New |
Headers | show |
Series | [bug#50614,core-updates] build: utils: Add ‘optional’ macro. | expand |
Context | Check | Description |
---|---|---|
cbaines/applying patch | fail | View Laminar job |
cbaines/issue | success | View issue |
Hi, Am Donnerstag, den 16.09.2021, 09:11 +0200 schrieb Xinglu Chen: > * guix/build/utils.scm (optional): New syntax > * tests/build-utils.scm ("optional: expr1 is non-#f", optional: expr1 > is #f"): > Test it. > * guix.texi (Build Utilities): Document it. > --- > A common idiom I have seen is > > (if EXPR1 > EXPR2 > '()) > > with the ‘optional’ macro, one can just write > > (optional EXPR1 > EXPR2) > > I am not sure if ‘optional’ is the best name (it was inspired by > ‘lib.optional’ in Nixpkgs), feedback welcome! > > doc/guix.texi | 35 +++++++++++++++++++++++++++++++++++ > guix/build/utils.scm | 17 ++++++++++++++++- > tests/build-utils.scm | 8 ++++++++ > 3 files changed, 59 insertions(+), 1 deletion(-) > > diff --git a/doc/guix.texi b/doc/guix.texi > index 9a3e8ae12c..1bb9ddb397 100644 > --- a/doc/guix.texi > +++ b/doc/guix.texi > @@ -8801,6 +8801,41 @@ in a build phase of the @code{wireguard-tools} > package: > `("PATH" ":" prefix ,(list coreutils)))))) > @end lisp > > +@subsection Miscellaneous build utilities > + > +@cindex miscellaneous build utilities > +This section documents some miscellaneous utilities that are useful > to +have. > + > +@deffn {Scheme Syntax} optional @var{test} @var{consequent} > +Like @code{when} (@pxref{Conditionals,,, guile, GNU Guile Reference > +Manual}), but if @var{test} evaluates to false, return the empty > list. > +This is replaces the following idiom: > +@end deffn > + > +@lisp > +(if @var{test} > + @var{consequent} > + '()) > +@end lisp > + > +with this: > + > +@lisp > +(optional @var{test} > + @var{consequent}) > +@end lisp > + > +It can be useful when certain targets require an additional > configure > +flags, e.g., > + > +@lisp > +(arguments > + `(#:configure-flags (list "--localstatedir=/var" > + "--sysconfdir=/etc" > + ,@@(optional (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..ecf834461f 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 @@ > > make-desktop-entry-file > > - locale-category->string)) > + locale-category->string > + > + optional)) > > > ;;; > @@ -1613,6 +1616,18 @@ returned." > 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 optional > + (syntax-rules () > + ((_ expr1 expr2) > + (if expr1 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..44ad9bafc0 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 @@ print('hello world')")) > ("guile/bin" . ,(dirname (which "guile")))) > "guile")))) > > +(test-equal "optional: expr1 is non-#f" > + 'bar > + (optional 'foo 'bar)) > + > +(test-equal "optional: expr1 is #f" > + '() > + (optional #f 'bar)) > > (test-end) > > base-commit: 22f7d4bce1e694b7ac38e62410d76a6d46d96c5d Naming choice aside, I don't think I like the asymmetry behind having a plain symbol on the one side vs. an empty list. What about (list-if condition . rest), which evaluates to rest if condition is true and otherwise nil?
Hi, Xinglu Chen <public@yoctocell.xyz> writes: > * guix/build/utils.scm (optional): New syntax > * tests/build-utils.scm ("optional: expr1 is non-#f", optional: expr1 is #f"): > Test it. > * guix.texi (Build Utilities): Document it. > --- > A common idiom I have seen is > > (if EXPR1 > EXPR2 > '()) > > with the ‘optional’ macro, one can just write > > (optional EXPR1 > EXPR2) > > I am not sure if ‘optional’ is the best name (it was inspired by > ‘lib.optional’ in Nixpkgs), feedback welcome! I like the idea! But perhaps if we're getting rid of boilerplate, we should go all the way and make it so that instead of (if EXPR1 `(EXPR2 EXPR3) '()) we can write (optional EXPR1 EXPR2 EXPR3) What do you think? Also, maybe 'list-when' for the name? > +@deffn {Scheme Syntax} optional @var{test} @var{consequent} > +Like @code{when} (@pxref{Conditionals,,, guile, GNU Guile Reference > +Manual}), but if @var{test} evaluates to false, return the empty list. > +This is replaces the following idiom: ^ no "is" > +@end deffn > + > +@lisp > +(if @var{test} > + @var{consequent} > + '()) > +@end lisp > + > +with this: > + > +@lisp > +(optional @var{test} > + @var{consequent}) > +@end lisp > + > +It can be useful when certain targets require an additional configure ^ no "an" > +flags, e.g., > + > +@lisp > +(arguments > + `(#:configure-flags (list "--localstatedir=/var" > + "--sysconfdir=/etc" > + ,@@(optional (hurd-target?) '("--with-courage")))) ^ extra "@"? -- Sarah
diff --git a/doc/guix.texi b/doc/guix.texi index 9a3e8ae12c..1bb9ddb397 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -8801,6 +8801,41 @@ in a build phase of the @code{wireguard-tools} package: `("PATH" ":" prefix ,(list coreutils)))))) @end lisp +@subsection Miscellaneous build utilities + +@cindex miscellaneous build utilities +This section documents some miscellaneous utilities that are useful to +have. + +@deffn {Scheme Syntax} optional @var{test} @var{consequent} +Like @code{when} (@pxref{Conditionals,,, guile, GNU Guile Reference +Manual}), but if @var{test} evaluates to false, return the empty list. +This is replaces the following idiom: +@end deffn + +@lisp +(if @var{test} + @var{consequent} + '()) +@end lisp + +with this: + +@lisp +(optional @var{test} + @var{consequent}) +@end lisp + +It can be useful when certain targets require an additional configure +flags, e.g., + +@lisp +(arguments + `(#:configure-flags (list "--localstatedir=/var" + "--sysconfdir=/etc" + ,@@(optional (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..ecf834461f 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 @@ make-desktop-entry-file - locale-category->string)) + locale-category->string + + optional)) ;;; @@ -1613,6 +1616,18 @@ returned." 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 optional + (syntax-rules () + ((_ expr1 expr2) + (if expr1 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..44ad9bafc0 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 @@ print('hello world')")) ("guile/bin" . ,(dirname (which "guile")))) "guile")))) +(test-equal "optional: expr1 is non-#f" + 'bar + (optional 'foo 'bar)) + +(test-equal "optional: expr1 is #f" + '() + (optional #f 'bar)) (test-end)