Augment `build-expression->derivation' with #:modules; add `http-fetch'.

* guix/derivations.scm (imported-modules): New procedure.
  (build-expression->derivation): New keyword argument `modules'.
  Use `imported-modules' when MODULES is non-empty, and pass it with
  `-L' to GUILE.

* guix/build/http.scm, guix/http.scm, tests/builders.scm: New files.

1 files changed, 45 insertions, 0 deletions

diff --git a/guix/http.scm b/guix/http.scm
new file mode 100644
index 0000000000..21234b388f
--- /dev/null
+++ b/guix/http.scm
@@ -0,0 +1,45 @@
+;;; Guix --- Nix package management from Guile.         -*- coding: utf-8 -*-
+;;; Copyright (C) 2012 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of Guix.
+;;;
+;;; 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.
+;;;
+;;; 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 Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix http)
+  #:use-module (guix derivations)
+  #:use-module (guix utils)
+  #:export (http-fetch))
+
+;;; Commentary:
+;;;
+;;; Produce fixed-output derivations with data fetched over HTTP.
+;;;
+;;; Code:
+
+(define* (http-fetch store url hash-algo hash
+                     #:key name (system (%current-system)))
+  "Return the path of a fixed-output derivation in STORE that fetches URL,
+which is expected to have hash HASH of type HASH-ALGO (a symbol).  By
+default, the file name is the base name of URL; optionally, NAME can specify
+a different file name."
+  (define builder
+    `(begin
+       (use-modules (guix build http))
+       (http-fetch ,url %output)))
+
+  (build-expression->derivation store (or name (basename url)) system
+                                builder '()
+                                #:hash-algo hash-algo
+                                #:hash hash
+                                #:modules '((guix build http))))