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authorLudovic Courtès <ludo@gnu.org>2019-09-01 13:24:03 +0200
committerLudovic Courtès <ludo@gnu.org>2019-09-04 13:02:27 +0200
commit76073d29e11c71d3678efd44db646852b5502e55 (patch)
tree80a271a5d82bf9eb13cb4891638218f0ac5657c1 /guix/json.scm
parent91300526b7d9d775bd98a700ed3758420ef9eac6 (diff)
Add (guix json).
* guix/swh.scm (define-json-reader, define-json-mapping): Move to... * guix/json.scm: ... here. New file. * Makefile.am (MODULES): Add it.
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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2018, 2019 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)
+ #:export (define-json-mapping))
+
+;;; Commentary:
+;;;
+;;; Helpers to map JSON objects to SRFI-9 records. Taken from (guix swh).
+;;;
+;;; Code:
+
+(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) ...)))))
+
+(define-syntax-rule (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 ...) ...)))