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services: configuration: Support fields without default values.

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Not all fields in a configuration have a sensible default value.  This changes
makes it possible to omit a default value for a configuration field, requiring
the user to provide a value.

* gnu/services/configuration.scm (configuration-missing-field): New procedure.
(define-configuration): Make default value optional.

Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>
This commit is contained in:
Xinglu Chen 2021-05-01 13:24:43 +02:00 committed by Maxim Cournoyer
parent 7ae9ef3b54
commit d1caabbce7
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GPG key ID: 1260E46482E63562
1 changed files with 53 additions and 27 deletions
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80
gnu/services/configuration.scm
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@ -2,6 +2,7 @@
;;; Copyright © 2015 Andy Wingo <wingo@igalia.com>
;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
;;; Copyright © 2017, 2018 Clément Lassieur <clement@lassieur.org>
;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
;;;
;;; This file is part of GNU Guix.
;;;
@ -63,6 +64,10 @@ (define (configuration-field-error field val)
(define (configuration-missing-field kind field)
(configuration-error
(format #f "~a configuration missing required field ~a" kind field)))
(define (configuration-no-default-value kind field)
(configuration-error
(format #f "The field `~a' of the `~a' configuration record \
does not have a default value" field kind)))
(define-record-type* <configuration-field>
configuration-field make-configuration-field configuration-field?
@ -112,7 +117,7 @@ (define (serialize-maybe-stem field-name val)
(define-syntax define-configuration
(lambda (stx)
(syntax-case stx ()
((_ stem (field (field-type def) doc) ...)
((_ stem (field (field-type def ...) doc) ...)
(with-syntax (((field-getter ...)
(map (lambda (field)
(id #'stem #'stem #'- field))
@ -121,36 +126,57 @@ (define-syntax define-configuration
(map (lambda (type)
(id #'stem type #'?))
#'(field-type ...)))
((field-default ...)
(map (match-lambda
((field-type default-value)
default-value)
((field-type)
;; Quote `undefined' to prevent a possibly
;; unbound warning.
(syntax 'undefined)))
#'((field-type def ...) ...)))
((field-serializer ...)
(map (lambda (type)
(id #'stem #'serialize- type))
#'(field-type ...))))
#`(begin
(define-record-type* #,(id #'stem #'< #'stem #'>)
#,(id #'stem #'% #'stem)
#,(id #'stem #'make- #'stem)
#,(id #'stem #'stem #'?)
(%location #,(id #'stem #'-location)
(default (and=> (current-source-location)
source-properties->location))
(innate))
(field field-getter (default def))
...)
(define #,(id #'stem #'stem #'-fields)
(list (configuration-field
(name 'field)
(type 'field-type)
(getter field-getter)
(predicate field-predicate)
(serializer field-serializer)
(default-value-thunk (lambda () def))
(documentation doc))
...))
(define-syntax-rule (stem arg (... ...))
(let ((conf (#,(id #'stem #'% #'stem) arg (... ...))))
(validate-configuration conf
#,(id #'stem #'stem #'-fields))
conf))))))))
#`(begin
(define-record-type* #,(id #'stem #'< #'stem #'>)
#,(id #'stem #'% #'stem)
#,(id #'stem #'make- #'stem)
#,(id #'stem #'stem #'?)
(%location #,(id #'stem #'-location)
(default (and=> (current-source-location)
source-properties->location))
(innate))
#,@(map (lambda (name getter def)
(if (eq? (syntax->datum def) (quote 'undefined))
#`(#,name #,getter)
#`(#,name #,getter (default #,def))))
#'(field ...)
#'(field-getter ...)
#'(field-default ...)))
(define #,(id #'stem #'stem #'-fields)
(list (configuration-field
(name 'field)
(type 'field-type)
(getter field-getter)
(predicate field-predicate)
(serializer field-serializer)
(default-value-thunk
(lambda ()
(display '#,(id #'stem #'% #'stem))
(if (eq? (syntax->datum field-default)
'undefined)
(configuration-no-default-value
'#,(id #'stem #'% #'stem) 'field)
field-default)))
(documentation doc))
...))
(define-syntax-rule (stem arg (... ...))
(let ((conf (#,(id #'stem #'% #'stem) arg (... ...))))
(validate-configuration conf
#,(id #'stem #'stem #'-fields))
conf))))))))
(define (serialize-package field-name val)
"")