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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
;;;
;;; 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 (guix json)
#:use-module (json)
#:use-module (srfi srfi-9))
;;; Commentary:
;;;
;;; Helpers to map JSON objects to SRFI-9 records. Taken from (guix swh).
;;; This module is superseded by 'define-json-mapping' as found since version
;;; 4.2.0 of Guile-JSON and will be removed once migration is complete.
;;;
;;; Code:
(define-syntax define-as-needed
(lambda (s)
"Define the given syntax rule unless (json) already provides it."
(syntax-case s ()
((_ (macro args ...) body ...)
(if (module-defined? (resolve-interface '(json))
(syntax->datum #'macro))
#'(eval-when (expand load eval)
;; Re-export MACRO from (json).
(module-re-export! (current-module) '(macro)))
#'(begin
;; Using Guile-JSON < 4.2.0, so provide our own MACRO.
(define-syntax-rule (macro args ...)
body ...)
(eval-when (expand load eval)
(module-export! (current-module) '(macro)))))))))
(define-syntax-rule (define-json-reader json->record ctor spec ...)
"Define JSON->RECORD as a procedure that converts a JSON representation,
read from a port, string, or hash table, into a record created by CTOR and
following SPEC, a series of field specifications."
(define (json->record input)
(let ((table (cond ((port? input)
(json->scm input))
((string? input)
(json-string->scm input))
((or (null? input) (pair? input))
input))))
(let-syntax ((extract-field (syntax-rules ()
((_ table (field key json->value))
(json->value (assoc-ref table key)))
((_ table (field key))
(assoc-ref table key))
((_ table (field))
(assoc-ref table
(symbol->string 'field))))))
(ctor (extract-field table spec) ...)))))
;; For some reason we cannot just have colliding definitions of
;; 'define-json-mapping' (that leads to a build failure in users of this
;; module), hence the use of 'define-as-needed'.
(define-as-needed (define-json-mapping rtd ctor pred json->record
(field getter spec ...) ...)
"Define RTD as a record type with the given FIELDs and GETTERs, à la SRFI-9,
and define JSON->RECORD as a conversion from JSON to a record of this type."
(begin
(define-record-type rtd
(ctor field ...)
pred
(field getter) ...)
(define-json-reader json->record ctor
(field spec ...) ...)))