[bug#33448] [PATCH 2/3] describe: Add json format.

[Oleg Pykhalov <go.wigust@gmail.com>]

* guix/channels.scm (channel->json): New procedure.
* guix/scripts/describe.scm (%options): Add 'json' option.
(display-checkout-info, display-profile-info): Use 'channel->json'.
* doc/guix.texi (Invoking guix describe): Document this.
---
 doc/guix.texi             |  5 ++++-
 guix/channels.scm         | 12 ++++++++++++
 guix/scripts/describe.scm | 13 ++++++++++---
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 082e81bf7..3413eb30f 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -3273,7 +3273,10 @@ produce human-readable output;
 @item channels
 produce a list of channel specifications that can be passed to @command{guix
 pull -C} or installed as @file{~/.config/guix/channels.scm} (@pxref{Invoking
-guix pull}).
+guix pull});
+@item json
+@cindex JSON
+produce a list of channel specifications in JSON format.
 @end table
 
 @item --profile=@var{profile}
diff --git a/guix/channels.scm b/guix/channels.scm
index bfdbf470b..9f2c9103e 100644
--- a/guix/channels.scm
+++ b/guix/channels.scm
@@ -26,6 +26,7 @@
   #:use-module (guix derivations)
   #:use-module (guix store)
   #:use-module (guix i18n)
+  #:use-module (json)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9)
   #:use-module (srfi srfi-11)
@@ -39,7 +40,9 @@
             channel-commit
             channel-location
 
+            channel->json
             channel->sexp
+
             %default-channels
 
             channel-instance?
@@ -94,6 +97,15 @@
        (url ,url)
        (commit ,commit)))))
 
+(define channel->json
+  (match-lambda
+    (($ <channel> name url branch commit location)
+     (scm->json-string
+      (list
+       (cons 'name name)
+       (cons 'url url)
+       (cons 'commit commit))))))
+
 (define-record-type <channel-instance>
   (channel-instance channel commit checkout)
   channel-instance?
diff --git a/guix/scripts/describe.scm b/guix/scripts/describe.scm
index 6a30d19b1..d7e276769 100644
--- a/guix/scripts/describe.scm
+++ b/guix/scripts/describe.scm
@@ -39,7 +39,7 @@
   ;; Specifications of the command-line options.
   (list (option '(#\f "format") #t #f
                 (lambda (opt name arg result)
-                  (unless (member arg '("human" "channels"))
+                  (unless (member arg '("human" "channels" "json"))
                     (leave (G_ "~a: unsupported output format~%") arg))
                   (alist-cons 'format (string->symbol arg) result)))
         (option '(#\p "profile") #t #f
@@ -107,7 +107,12 @@ within a Git checkout."
       ('channels
        (pretty-print (channel->sexp (channel (name 'guix)
                                              (url (dirname directory))
-                                             (commit commit))))))
+                                             (commit commit)))))
+      ('json
+       (display (channel->json (channel (name 'guix)
+                                        (url (dirname directory))
+                                        (commit commit))))
+       (newline)))
     (display-package-search-path fmt)))
 
 (define (display-profile-info profile fmt)
@@ -144,7 +149,9 @@ in the format specified by FMT."
     ('human
      (display-profile-content profile number))
     ('channels
-     (pretty-print (map channel->sexp (channels)))))
+     (pretty-print (map channel->sexp (channels))))
+    ('json
+     (format #t "[~a]~%" (string-join (map channel->json (channels)) ","))))
   (display-package-search-path fmt))
 
 \f
-- 
2.19.1