maint: Add "make check-channel-news".

* build-aux/check-channel-news.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.
(check-channel-news): New phony rule.
* doc/contributing.texi (Commit Access): Mention "make check-channel-news".

Makefile.am

@@ -557,6 +557,7 @@ EXTRA_DIST +=						\
   build-aux/cuirass/guix-modular.scm			\
   build-aux/cuirass/hydra-to-cuirass.scm		\
   build-aux/check-final-inputs-self-contained.scm	\
+  build-aux/check-channel-news.scm			\
   build-aux/compile-as-derivation.scm			\
   build-aux/generate-authors.scm			\
   build-aux/git-authenticate.scm			\
@@ -885,6 +886,11 @@ assert-final-inputs-self-contained: $(GOBJECTS)
 	$(AM_V_at)$(top_builddir)/pre-inst-env "$(GUILE)"			\
 	  "$(top_srcdir)/build-aux/check-final-inputs-self-contained.scm"
 
+# Validate channel news.
+check-channel-news: $(GOBJECTS)
+	$(AM_V_at)$(top_builddir)/pre-inst-env "$(GUILE)"	\
+	  "$(top_srcdir)/build-aux/check-channel-news.scm"
+
 # Compute the Hydra jobs and write them in the target file.
 hydra-jobs.scm: $(GOBJECTS)
 	$(AM_V_at)$(MKDIR_P) "`dirname "$@"`"
@@ -904,7 +910,7 @@ cuirass-jobs.scm: $(GOBJECTS)
 
 .PHONY: gen-ChangeLog gen-AUTHORS gen-tarball-version
 .PHONY: assert-no-store-file-names assert-binaries-available
-.PHONY: assert-final-inputs-self-contained
+.PHONY: assert-final-inputs-self-contained check-channel-news
 .PHONY: clean-go make-go as-derivation authenticate
 .PHONY: update-guix-package update-NEWS release
 

build-aux/check-channel-news.scm

@@ -0,0 +1,82 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 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/>.
+
+;;;
+;;; Validate 'etc/news.scm'.
+;;;
+
+(use-modules (git)
+             (guix git)
+             (guix ui)
+             (guix channels)
+             (srfi srfi-26)
+             (ice-9 match))
+
+;; XXX: These two things are currently private.
+(define read-channel-news (@@ (guix channels) read-channel-news))
+(define channel-news-entries (cut struct-ref <> 0))
+
+(define (all-the-news directory)
+  "Return the <channel-news> read from DIRECTORY, a checkout of the 'guix'
+channel."
+  (call-with-input-file (string-append directory "/etc/news.scm")
+    read-channel-news))
+
+(define (validate-texinfo str type language)
+  "Parse STR as a Texinfo fragment and raise an error if that fails."
+  (catch #t
+    (lambda ()
+      (texi->plain-text str))
+    (lambda (key . args)
+      (print-exception (current-error-port) #f key args)
+      (report-error (G_ "the Texinfo snippet below is invalid (~a, ~a):~%")
+                    type language)
+      (display str (current-error-port))
+      (exit 1))))
+
+(define (validate-news-entry repository entry)
+  "Validate ENTRY, a <channel-news-entry>, making sure it refers to an
+existent commit of REPOSITORY and contains only valid Texinfo."
+  (catch 'git-error
+    (lambda ()
+      (let ((commit (commit-lookup repository
+                                   (string->oid
+                                    (channel-news-entry-commit entry)))))
+        (for-each (match-lambda
+                    ((language . title)
+                     (validate-texinfo title 'title language)))
+                  (channel-news-entry-title entry))
+        (for-each (match-lambda
+                    ((language . body)
+                     (validate-texinfo body 'body language)))
+                  (channel-news-entry-body entry))))
+    (lambda (key error . rest)
+      (if (= GIT_ENOTFOUND (git-error-code error))
+          (leave (G_ "commit '~a' of entry '~a' does not exist~%")
+                 (channel-news-entry-commit entry)
+                 (channel-news-entry-title entry))
+          (apply throw key error rest)))))
+
+(let* ((this-directory (dirname (current-filename)))
+       (top-directory  (string-append this-directory "/.."))
+       (entries        (channel-news-entries (all-the-news top-directory))))
+  (with-repository top-directory repository
+    (for-each (cut validate-news-entry repository <>)
+              entries)
+    (info (G_ "All ~a channel news entries are valid.~%")
+          (length entries))))

doc/contributing.texi

@@ -1278,6 +1278,14 @@ When pushing a commit on behalf of somebody else, please add a
 with @command{git am --signoff}.  This improves tracking of who did
 what.
 
+When adding channel news entries (@pxref{Channels, Writing Channel
+News}), make sure they are well-formed by running the following command
+right before pushing:
+
+@example
+make check-channel-news
+@end example
+
 For anything else, please post to @email{guix-patches@@gnu.org} and
 leave time for a review, without committing anything (@pxref{Submitting
 Patches}).  If you didn’t receive any reply after two weeks, and if