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.

Makefile.am

@@ -68,6 +68,7 @@ MODULES =					\
   guix/cpio.scm					\
   guix/deprecation.scm				\
   guix/docker.scm	   			\
+  guix/json.scm					\
   guix/records.scm				\
   guix/pki.scm					\
   guix/progress.scm				\

guix/json.scm

@@ -0,0 +1,62 @@
+;;; 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 ...) ...)))

guix/swh.scm

@@ -21,6 +21,7 @@ (define-module (guix swh)
   #:use-module (guix build utils)
   #:use-module ((guix build syscalls) #:select (mkdtemp!))
   #:use-module (web uri)
+  #:use-module (guix json)
   #:use-module (web client)
   #:use-module (web response)
   #:use-module (json)
@@ -135,40 +136,6 @@ (define url
       url
       (string-append url "/")))
 
-(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 ...) ...)))
-
 (define %date-regexp
   ;; Match strings like "2014-11-17T22:09:38+01:00" or
   ;; "2018-09-30T23:20:07.815449+00:00"".