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guix/gnu/services/configuration.scm

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;;; GNU Guix --- Functional package management for GNU
;;; 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>
;;; Copyright © 2021, 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com>
;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
;;; Copyright © 2022 Maxime Devos <maximedevos@telenet.be>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (gnu services configuration)
#:use-module (guix packages)
#:use-module (guix records)
#:use-module (guix gexp)
#:use-module ((guix utils) #:select (source-properties->location))
#:use-module ((guix diagnostics)
#:select (formatted-message location-file &error-location))
#:use-module ((guix modules) #:select (file-name->module-name))
#:use-module (guix i18n)
#:autoload (texinfo) (texi-fragment->stexi)
#:autoload (texinfo serialize) (stexi->texi)
#:use-module (ice-9 curried-definitions)
#:use-module (ice-9 match)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-34)
#:use-module (srfi srfi-35)
#:export (configuration-field
configuration-field-name
configuration-field-type
configuration-missing-field
configuration-field-error
configuration-field-serializer
configuration-field-getter
configuration-field-default-value-thunk
configuration-field-documentation
configuration-error?
define-configuration
define-configuration/no-serialization
no-serialization
serialize-configuration
define-maybe
define-maybe/no-serialization
%unset-value
maybe-value
maybe-value-set?
generate-documentation
configuration->documentation
empty-serializer
serialize-package
filter-configuration-fields
interpose
list-of
list-of-strings?
alist?
serialize-file-like
text-config?
serialize-text-config
generic-serialize-alist-entry
generic-serialize-alist))
;;; Commentary:
;;;
;;; Syntax for creating Scheme bindings to complex configuration files.
;;;
;;; Code:
(define-condition-type &configuration-error &error
configuration-error?)
(define (configuration-error message)
(raise (condition (&message (message message))
(&configuration-error))))
(define (configuration-field-error loc field value)
(raise (apply
make-compound-condition
(formatted-message (G_ "invalid value ~s for field '~a'")
value field)
(condition (&configuration-error))
(if loc
(list (condition
(&error-location (location loc))))
'()))))
(define (configuration-missing-field kind field)
(configuration-error
(format #f "~a configuration missing required field ~a" kind field)))
(define (configuration-missing-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?
(name configuration-field-name)
(type configuration-field-type)
(getter configuration-field-getter)
(predicate configuration-field-predicate)
(serializer configuration-field-serializer)
(default-value-thunk configuration-field-default-value-thunk)
(documentation configuration-field-documentation))
(define (serialize-configuration config fields)
#~(string-append
#$@(map (lambda (field)
((configuration-field-serializer field)
(configuration-field-name field)
((configuration-field-getter field) config)))
fields)))
(define-syntax-rule (id ctx parts ...)
"Assemble PARTS into a raw (unhygienic) identifier."
(datum->syntax ctx (symbol-append (syntax->datum parts) ...)))
(define (define-maybe-helper serialize? prefix syn)
(syntax-case syn ()
((_ stem)
(with-syntax
((stem? (id #'stem #'stem #'?))
(maybe-stem? (id #'stem #'maybe- #'stem #'?))
(serialize-stem (if prefix
(id #'stem prefix #'serialize- #'stem)
(id #'stem #'serialize- #'stem)))
(serialize-maybe-stem (if prefix
(id #'stem prefix #'serialize-maybe- #'stem)
(id #'stem #'serialize-maybe- #'stem))))
#`(begin
(define (maybe-stem? val)
(or (not (maybe-value-set? val))
(stem? val)))
#,@(if serialize?
(list #'(define (serialize-maybe-stem field-name val)
(if (stem? val)
(serialize-stem field-name val)
"")))
'()))))))
(define-syntax define-maybe
(lambda (x)
(syntax-case x (no-serialization prefix)
((_ stem (no-serialization))
(define-maybe-helper #f #f #'(_ stem)))
((_ stem (prefix serializer-prefix))
(define-maybe-helper #t #'serializer-prefix #'(_ stem)))
((_ stem)
(define-maybe-helper #t #f #'(_ stem))))))
(define-syntax-rule (define-maybe/no-serialization stem)
(define-maybe stem (no-serialization)))
(define (normalize-field-type+def s)
(syntax-case s ()
((field-type def)
(identifier? #'field-type)
(values #'(field-type def)))
((field-type)
(identifier? #'field-type)
(values #'(field-type %unset-value)))
(field-type
(identifier? #'field-type)
(values #'(field-type %unset-value)))))
(define (define-configuration-helper serialize? serializer-prefix syn)
(syntax-case syn ()
((_ stem (field field-type+def doc custom-serializer ...) ...)
(with-syntax
((((field-type def) ...)
(map normalize-field-type+def #'(field-type+def ...))))
(with-syntax
(((field-getter ...)
(map (lambda (field)
(id #'stem #'stem #'- field))
#'(field ...)))
((field-predicate ...)
(map (lambda (type)
(id #'stem type #'?))
#'(field-type ...)))
((field-default ...)
(map (match-lambda
((field-type default-value)
default-value))
#'((field-type def) ...)))
((field-serializer ...)
(map (lambda (type custom-serializer)
(and serialize?
(match custom-serializer
((serializer)
serializer)
(()
(if serializer-prefix
(id #'stem
serializer-prefix
#'serialize- type)
(id #'stem #'serialize- type))))))
#'(field-type ...)
#'((custom-serializer ...) ...))))
(define (field-sanitizer name pred)
;; Define a macro for use as a record field sanitizer, where NAME
;; is the name of the field and PRED is the predicate that tells
;; whether a value is valid for this field.
#`(define-syntax #,(id #'stem #'validate- #'stem #'- name)
(lambda (s)
;; Make sure the given VALUE, for field NAME, passes PRED.
(syntax-case s ()
((_ value)
(with-syntax ((name #'#,name)
(pred #'#,pred)
(loc (datum->syntax #'value
(syntax-source #'value))))
#'(if (pred value)
value
(configuration-field-error
(and=> 'loc source-properties->location)
'name value))))))))
#`(begin
;; Define field validation macros.
#,@(map field-sanitizer
#'(field ...)
#'(field-predicate ...))
(define-record-type* #,(id #'stem #'< #'stem #'>)
stem
#,(id #'stem #'make- #'stem)
#,(id #'stem #'stem #'?)
#,@(map (lambda (name getter def)
#`(#,name #,getter (default #,def)
(sanitize
#,(id #'stem #'validate- #'stem #'- name))))
#'(field ...)
#'(field-getter ...)
#'(field-default ...))
(%location #,(id #'stem #'stem #'-location)
(default (and=> (current-source-location)
source-properties->location))
(innate)))
(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 (maybe-value-set? (syntax->datum field-default))
field-default
(configuration-missing-default-value
'#,(id #'stem #'% #'stem) 'field))))
(documentation doc))
...))))))))
(define no-serialization ;syntactic keyword for 'define-configuration'
'(no serialization))
(define-syntax define-configuration
(lambda (s)
(syntax-case s (no-serialization prefix)
((_ stem (field field-type+def doc custom-serializer ...) ...
(no-serialization))
(define-configuration-helper
#f #f #'(_ stem (field field-type+def doc custom-serializer ...)
...)))
((_ stem (field field-type+def doc custom-serializer ...) ...
(prefix serializer-prefix))
(define-configuration-helper
#t #'serializer-prefix #'(_ stem (field field-type+def
doc custom-serializer ...)
...)))
((_ stem (field field-type+def doc custom-serializer ...) ...)
(define-configuration-helper
#t #f #'(_ stem (field field-type+def doc custom-serializer ...)
...))))))
(define-syntax-rule (define-configuration/no-serialization
stem (field field-type+def
doc custom-serializer ...) ...)
(define-configuration stem (field field-type+def
doc custom-serializer ...) ...
(no-serialization)))
(define (empty-serializer field-name val) "")
(define serialize-package empty-serializer)
;; Ideally this should be an implementation detail, but we export it
;; to provide a simpler API that enables unsetting a configuration
;; field that has a maybe type, but also a default value. We give it
;; a value that sticks out to the reader when something goes wrong.
;;
;; An example use-case would be something like a network application
;; that uses a default port, but the field can explicitly be unset to
;; request a random port at startup.
(define %unset-value '%unset-marker%)
(define (maybe-value-set? value)
"Predicate to check whether a 'maybe' value was explicitly provided."
(not (eq? %unset-value value)))
;; Ideally there should be a compiler macro for this predicate, that expands
;; to a conditional that only instantiates the default value when needed.
(define* (maybe-value value #:optional (default #f))
"Returns VALUE, unless it is the unset value, in which case it returns
DEFAULT."
(if (maybe-value-set? value)
value
default))
;; A little helper to make it easier to document all those fields.
(define (generate-documentation documentation documentation-name)
(define (str x) (object->string x))
(define (package->symbol package)
"Return the first symbol name of a package that matches PACKAGE, else #f."
(let* ((module (file-name->module-name
(location-file (package-location package))))
(symbols (filter-map
identity
(module-map (lambda (symbol var)
(and (equal? package (variable-ref var))
symbol))
(resolve-module module)))))
(if (null? symbols)
#f
(first symbols))))
(define (generate configuration-name)
(match (assq-ref documentation configuration-name)
((fields . sub-documentation)
`((deftp (% (category "Data Type") (name ,(str configuration-name)))
(para "Available " (code ,(str configuration-name)) " fields are:")
(table
(% (formatter (asis)))
,@(map
(lambda (f)
(let ((field-name (configuration-field-name f))
(field-type (configuration-field-type f))
(field-docs (cdr (texi-fragment->stexi
(configuration-field-documentation f))))
(default (catch #t
(configuration-field-default-value-thunk f)
(lambda _ '%invalid))))
(define (show-default? val)
(or (string? val) (number? val) (boolean? val)
(package? val)
(and (symbol? val) (not (eq? val '%invalid)))
(and (list? val) (and-map show-default? val))))
(define (show-default val)
(cond
((package? val)
(symbol->string (package->symbol val)))
(else (str val))))
`(entry (% (heading
(code ,(str field-name))
,@(if (show-default? default)
`(" (default: "
(code ,(show-default default)) ")")
'())
" (type: " ,(str field-type) ")"))
(para ,@field-docs)
,@(append-map
generate
(or (assq-ref sub-documentation field-name)
'())))))
fields)))))))
(stexi->texi `(*fragment* . ,(generate documentation-name))))
(define (configuration->documentation configuration-symbol)
"Take CONFIGURATION-SYMBOL, the symbol corresponding to the name used when
defining a configuration record with DEFINE-CONFIGURATION, and output the
Texinfo documentation of its fields."
;; This is helper for a simple, straight-forward application of
;; GENERATE-DOCUMENTATION.
(let ((fields-getter (module-ref (current-module)
(symbol-append configuration-symbol
'-fields))))
(display (generate-documentation `((,configuration-symbol ,fields-getter))
configuration-symbol))))
(define* (filter-configuration-fields configuration-fields fields
#:optional negate?)
"Retrieve the fields listed in FIELDS from CONFIGURATION-FIELDS.
If NEGATE? is @code{#t}, retrieve all fields except FIELDS."
(filter (lambda (field)
(let ((member? (member (configuration-field-name field) fields)))
(if (not negate?) member? (not member?))))
configuration-fields))
(define* (interpose ls #:optional (delimiter "\n") (grammar 'infix))
"Same as @code{string-join}, but without join and string, returns a
DELIMITER interposed LS. Support 'infix and 'suffix GRAMMAR values."
(when (not (member grammar '(infix suffix)))
(raise
(formatted-message
(G_ "The GRAMMAR value must be 'infix or 'suffix, but ~a provided.")
grammar)))
(fold-right (lambda (e acc)
(cons e
(if (and (null? acc) (eq? grammar 'infix))
acc
(cons delimiter acc))))
'() ls))
(define (list-of pred?)
"Return a procedure that takes a list and check if all the elements of
the list result in @code{#t} when applying PRED? on them."
(lambda (x)
(if (list? x)
(every pred? x)
#f)))
(define list-of-strings?
(list-of string?))
(define alist? list?)
(define serialize-file-like empty-serializer)
(define (text-config? config)
(list-of file-like?))
(define (serialize-text-config field-name val)
#~(string-append
#$@(interpose
(map
(lambda (e)
#~(begin
(use-modules (ice-9 rdelim))
(with-fluids ((%default-port-encoding "UTF-8"))
(with-input-from-file #$e read-string))))
val)
"\n" 'suffix)))
(define ((generic-serialize-alist-entry serialize-field) entry)
"Apply the SERIALIZE-FIELD procedure on the field and value of ENTRY."
(match entry
((field . val) (serialize-field field val))))
(define (generic-serialize-alist combine serialize-field fields)
"Generate a configuration from an association list FIELDS.
SERIALIZE-FIELD is a procedure that takes two arguments, it will be
applied on the fields and values of FIELDS using the
@code{generic-serialize-alist-entry} procedure.
COMBINE is a procedure that takes one or more arguments and combines
all the alist entries into one value, @code{string-append} or
@code{append} are usually good candidates for this.
See the @code{serialize-alist} procedure in `@code{(gnu home services
version-control}' for an example usage.)}"
(apply combine
(map (generic-serialize-alist-entry serialize-field) fields)))
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