guix: Add support for channel dependencies.

* guix/channels.scm (<channel-metadata>): New record.
(read-channel-metadata, channel-instance-dependencies): New procedures.
(latest-channel-instances): Include channel dependencies; add optional
argument PREVIOUS-CHANNELS.
(channel-instance-derivations): Build derivation for additional channels and
add it as dependency to the channel instance derivation.
* doc/guix.texi (Channels): Add subsection "Declaring Channel Dependencies".
* tests/channels.scm: New file.
* Makefile.am (SCM_TESTS): Add it.

1 files changed, 139 insertions, 0 deletions

diff --git a/tests/channels.scm b/tests/channels.scm
new file mode 100644
index 00000000000..f3fc383ac31
--- /dev/null
+++ b/tests/channels.scm
@@ -0,0 +1,139 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2018 Ricardo Wurmus <rekado@elephly.net>
+;;;
+;;; 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 (test-channels)
+  #:use-module (guix channels)
+  #:use-module ((guix build syscalls) #:select (mkdtemp!))
+  #:use-module (guix tests)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-64)
+  #:use-module (ice-9 match))
+
+(test-begin "channels")
+
+(define* (make-instance #:key
+                        (name 'fake)
+                        (commit "cafebabe")
+                        (spec #f))
+  (define instance-dir (mkdtemp! "/tmp/checkout.XXXXXX"))
+  (and spec
+       (with-output-to-file (string-append instance-dir "/.guix-channel")
+         (lambda _ (format #t "~a" spec))))
+  ((@@ (guix channels) channel-instance)
+   name commit instance-dir))
+
+(define instance--boring (make-instance))
+(define instance--no-deps
+  (make-instance #:spec
+                 '(channel
+                   (version 0)
+                   (dependencies
+                    (channel
+                     (name test-channel)
+                     (url "https://example.com/test-channel"))))))
+(define instance--simple
+  (make-instance #:spec
+                 '(channel
+                   (version 0)
+                   (dependencies
+                    (channel
+                     (name test-channel)
+                     (url "https://example.com/test-channel"))))))
+(define instance--with-dupes
+  (make-instance #:spec
+                 '(channel
+                   (version 0)
+                   (dependencies
+                    (channel
+                     (name test-channel)
+                     (url "https://example.com/test-channel"))
+                    (channel
+                     (name test-channel)
+                     (url "https://example.com/test-channel")
+                     (commit "abc1234"))
+                    (channel
+                     (name test-channel)
+                     (url "https://example.com/test-channel-elsewhere"))))))
+
+(define read-channel-metadata
+  (@@ (guix channels) read-channel-metadata))
+
+
+(test-equal "read-channel-metadata returns #f if .guix-channel does not exist"
+  #f
+  (read-channel-metadata instance--boring))
+
+(test-assert "read-channel-metadata returns <channel-metadata>"
+  (every (@@ (guix channels) channel-metadata?)
+         (map read-channel-metadata
+              (list instance--no-deps
+                    instance--simple
+                    instance--with-dupes))))
+
+(test-assert "read-channel-metadata dependencies are channels"
+  (let ((deps ((@@ (guix channels) channel-metadata-dependencies)
+               (read-channel-metadata instance--simple))))
+    (match deps
+      (((? channel? dep)) #t)
+      (_ #f))))
+
+(test-assert "latest-channel-instances includes channel dependencies"
+  (let* ((channel (channel
+                   (name 'test)
+                   (url "test")))
+         (test-dir (channel-instance-checkout instance--simple)))
+    (mock ((guix git) latest-repository-commit
+           (lambda* (store url #:key ref)
+             (match url
+               ("test" (values test-dir 'whatever))
+               (_ (values "/not-important" 'not-important)))))
+          (let ((instances (latest-channel-instances #f (list channel))))
+            (and (eq? 2 (length instances))
+                 (lset= eq?
+                        '(test test-channel)
+                        (map (compose channel-name channel-instance-channel)
+                             instances)))))))
+
+(test-assert "latest-channel-instances excludes duplicate channel dependencies"
+  (let* ((channel (channel
+                   (name 'test)
+                   (url "test")))
+         (test-dir (channel-instance-checkout instance--with-dupes)))
+    (mock ((guix git) latest-repository-commit
+           (lambda* (store url #:key ref)
+             (match url
+               ("test" (values test-dir 'whatever))
+               (_ (values "/not-important" 'not-important)))))
+          (let ((instances (latest-channel-instances #f (list channel))))
+            (and (eq? 2 (length instances))
+                 (lset= eq?
+                        '(test test-channel)
+                        (map (compose channel-name channel-instance-channel)
+                             instances))
+                 ;; only the most specific channel dependency should remain,
+                 ;; i.e. the one with a specified commit.
+                 (find (lambda (instance)
+                         (and (eq? (channel-name
+                                    (channel-instance-channel instance))
+                                   'test-channel)
+                              (eq? (channel-commit
+                                    (channel-instance-channel instance))
+                                   'abc1234)))
+                       instances))))))
+
+(test-end "channels")