import: Add hackage importer.

* guix/scripts/import.scm (importers): Add hackage.
* guix/scripts/import/hackage.scm: New file.
* po/guix/POTFILES.in: Add guix/scripts/import.scm.
* doc/guix.texi: Add section on 'hackage' importer.

doc/guix.texi

@@ -3188,6 +3188,37 @@ bound to the @code{libreoffice} top-level attribute):
 @example
 guix import nix ~/path/to/nixpkgs libreoffice
 @end example
+
+@item hackage
+@cindex hackage
+Import meta-data from Haskell community's central package archive
+@uref{https://hackage.haskell.org/, Hackage}.  Information is taken from
+Cabal files and includes all the relevant information, including package
+dependencies.
+
+Specific command-line options are:
+
+@table @code
+@item --no-test-dependencies
+@itemx -t
+Do not include dependencies only required to run the test suite.
+@end table
+
+The command below imports meta-data for the latest version of the
+@code{HTTP} Haskell package without including test dependencies:
+
+@example
+guix import hackage -t HTTP
+@end example
+
+A specific package version may optionally be specified by following the
+package name by a hyphen and a version number as in the following example:
+
+@example
+guix import hackage mtl-2.1.3.1
+@end example
+
+Currently only indentation structured Cabal files are supported.
 @end table
 
 The structure of the @command{guix import} code is modular.  It would be

guix/scripts/import.scm

@@ -73,7 +73,7 @@ rather than \\n."
 ;;; Entry point.
 ;;;
 
-(define importers '("gnu" "nix" "pypi" "cpan"))
+(define importers '("gnu" "nix" "pypi" "cpan" "hackage"))
 
 (define (resolve-importer name)
   (let ((module (resolve-interface

guix/scripts/import/hackage.scm

@@ -0,0 +1,106 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2015 Federico Beffa <beffa@fbengineering.ch>
+;;;
+;;; 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 scripts import hackage)
+  #:use-module (guix ui)
+  #:use-module (guix utils)
+  #:use-module (guix import hackage)
+  #:use-module (guix scripts import)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-37)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 format)
+  #:export (guix-import-hackage))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  '((include-test-dependencies? . #t)))
+
+(define (show-help)
+  (display (_ "Usage: guix import hackage PACKAGE-NAME
+Import and convert the Hackage package for PACKAGE-NAME.  If PACKAGE-NAME
+includes a suffix constituted by a dash followed by a numerical version (as
+used with Guix packages), then a definition for the specified version of the
+package will be generated.  If no version suffix is pecified, then the
+generated package definition will correspond to the latest available
+version.\n"))
+  (display (_ "
+  -h, --help                   display this help and exit"))
+  (display (_ "
+  -t, --no-test-dependencies   don't include test only dependencies"))
+  (display (_ "
+  -V, --version                display version information and exit"))
+  (newline)
+  (show-bug-report-information))
+
+(define %options
+  ;; Specification of the command-line options.
+  (cons* (option '(#\h "help") #f #f
+                 (lambda args
+                   (show-help)
+                   (exit 0)))
+         (option '(#\V "version") #f #f
+                 (lambda args
+                   (show-version-and-exit "guix import hackage")))
+         (option '(#\t "no-test-dependencies") #f #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'include-test-dependencies? #f
+                               (alist-delete 'include-test-dependencies?
+                                             result))))
+         %standard-import-options))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-import-hackage . args)
+  (define (parse-options)
+    ;; Return the alist of option values.
+    (args-fold* args %options
+                (lambda (opt name arg result)
+                  (leave (_ "~A: unrecognized option~%") name))
+                (lambda (arg result)
+                  (alist-cons 'argument arg result))
+                %default-options))
+
+  (let* ((opts (parse-options))
+         (args (filter-map (match-lambda
+                            (('argument . value)
+                             value)
+                            (_ #f))
+                           (reverse opts))))
+    (match args
+      ((package-name)
+       (let ((sexp (hackage->guix-package
+                    package-name
+                    #:include-test-dependencies?
+                    (assoc-ref opts 'include-test-dependencies?))))
+         (unless sexp
+           (leave (_ "failed to download cabal file for package '~a'~%")
+                  package-name))
+         sexp))
+      (()
+       (leave (_ "too few arguments~%")))
+      ((many ...)
+       (leave (_ "too many arguments~%"))))))

po/guix/POTFILES.in

@@ -8,6 +8,7 @@ guix/scripts/download.scm
 guix/scripts/package.scm
 guix/scripts/gc.scm
 guix/scripts/hash.scm
+guix/scripts/import.scm
 guix/scripts/pull.scm
 guix/scripts/substitute.scm
 guix/scripts/authenticate.scm