import: Add stackage importer and updater.

* guix/import/stackage.scm: New file.
* guix/scripts/import/stackage.scm: New file.
* Makefile.am (MODULES): Add new files.
* guix/scripts/import.scm (importers): Add "stackage".
* guix/scripts/refresh.scm (%updaters): Add %stackage-updater.
* doc/guix.texi (Invoking 'guix import'): Document the importer.
  (Invoking 'guix refresh'): Add stackage to option --type valid values.
* guix/import/hackage.scm (guix-package->hackage-name, hackage-fetch,
  hackage-source-url, hackage-cabal-url, hackage-package?): Export them.

7 files changed, 294 insertions, 3 deletions

diff --git a/Makefile.am b/Makefile.am
index 360c356f10..18501bddfc 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -126,6 +126,7 @@ MODULES =					\
   guix/import/cabal.scm				\
   guix/import/cran.scm				\
   guix/import/hackage.scm			\
+  guix/import/stackage.scm			\
   guix/import/elpa.scm   			\
   guix/scripts.scm				\
   guix/scripts/download.scm			\
@@ -147,6 +148,7 @@ MODULES =					\
   guix/scripts/import/gnu.scm			\
   guix/scripts/import/nix.scm			\
   guix/scripts/import/hackage.scm		\
+  guix/scripts/import/stackage.scm		\
   guix/scripts/import/elpa.scm  		\
   guix/scripts/environment.scm			\
   guix/scripts/publish.scm			\
diff --git a/doc/guix.texi b/doc/guix.texi
index 21082aece4..eca2d99487 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -31,7 +31,8 @@ Copyright @copyright{} 2016 Jan Nieuwenhuizen@*
 Copyright @copyright{} 2016 Julien Lepiller@*
 Copyright @copyright{} 2016 Alex ter Weele@*
 Copyright @copyright{} 2017 Clément Lassieur@*
-Copyright @copyright{} 2017 Mathieu Othacehe
+Copyright @copyright{} 2017 Mathieu Othacehe@*
+Copyright @copyright{} 2017 Federico Beffa
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -5340,6 +5341,34 @@ package name by an at-sign and a version number as in the following example:
 guix import hackage mtl@@2.1.3.1
 @end example
 
+@item stackage
+@cindex stackage
+The @code{stackage} importer is a wrapper around the @code{hackage} one.
+It takes a package name, looks up the package version included in a
+long-term support (LTS) @uref{https://www.stackage.org, Stackage}
+release and uses the @code{hackage} importer to retrieve its metadata.
+Note that it is up to you to select an LTS release compatible with the
+GHC compiler used by Guix.
+
+Specific command-line options are:
+
+@table @code
+@item --no-test-dependencies
+@itemx -t
+Do not include dependencies required only by the test suites.
+@item --lts-version=@var{version}
+@itemx -r @var{version}
+@var{version} is the desired LTS release version.  If omitted the latest
+release is used.
+@end table
+
+The command below imports metadata for the @code{HTTP} Haskell package
+included in the LTS Stackage release version 7.18:
+
+@example
+guix import stackage --lts-version=7.18 HTTP
+@end example
+
 @item elpa
 @cindex elpa
 Import metadata from an Emacs Lisp Package Archive (ELPA) package
@@ -5504,6 +5533,8 @@ the updater for @uref{https://rubygems.org, RubyGems} packages.
 the updater for @uref{https://github.com, GitHub} packages.
 @item hackage
 the updater for @uref{https://hackage.haskell.org, Hackage} packages.
+@item stackage
+the updater for @uref{https://www.stackage.org, Stackage} packages.
 @item crate
 the updater for @uref{https://crates.io, Crates} packages.
 @end table
diff --git a/guix/import/hackage.scm b/guix/import/hackage.scm
index 9af78ea888..4d01ed23ea 100644
--- a/guix/import/hackage.scm
+++ b/guix/import/hackage.scm
@@ -37,7 +37,13 @@
   #:use-module (guix packages)
   #:use-module ((guix utils) #:select (call-with-temporary-output-file))
   #:export (hackage->guix-package
-            %hackage-updater))
+            %hackage-updater
+
+            guix-package->hackage-name
+            hackage-fetch
+            hackage-source-url
+            hackage-cabal-url
+            hackage-package?))
 
 (define ghc-standard-libraries
   ;; List of libraries distributed with ghc (7.10.2). We include GHC itself as
diff --git a/guix/import/stackage.scm b/guix/import/stackage.scm
new file mode 100644
index 0000000000..542b718083
--- /dev/null
+++ b/guix/import/stackage.scm
@@ -0,0 +1,135 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 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 import stackage)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:use-module (guix import json)
+  #:use-module (guix import hackage)
+  #:use-module (guix memoization)
+  #:use-module (guix packages)
+  #:use-module (guix upstream)
+  #:use-module (guix ui)
+  #:export (stackage->guix-package
+            %stackage-updater))
+
+
+;;;
+;;; Stackage info fetcher and access functions
+;;;
+
+(define %stackage-url "http://www.stackage.org")
+
+(define (lts-info-ghc-version lts-info)
+  "Retruns the version of the GHC compiler contained in LTS-INFO."
+  (match lts-info
+    ((("snapshot" ("ghc" . version) _ _) _)  version)
+    (_ #f)))
+
+(define (lts-info-packages lts-info)
+  "Retruns the alist of packages contained in LTS-INFO."
+  (match lts-info
+    ((_ ("packages" pkg ...)) pkg)
+    (_ '())))
+
+(define stackage-lts-info-fetch
+  ;; "Retrieve the information about the LTS Stackage release VERSION."
+  (memoize
+   (lambda* (#:optional (version ""))
+     (let* ((url (if (string=? "" version)
+                     (string-append %stackage-url "/lts")
+                     (string-append %stackage-url "/lts-" version)))
+            (lts-info (json-fetch url)))
+       (if lts-info
+           (reverse lts-info)
+           (leave (_ "LTS release version not found: ~A~%") version))))))
+
+(define (stackage-package-name pkg-info)
+  (assoc-ref pkg-info "name"))
+
+(define (stackage-package-version pkg-info)
+  (assoc-ref pkg-info "version"))
+
+(define (lts-package-version pkgs-info name)
+  "Return the version of the package with upstream NAME included in PKGS-INFO."
+  (let ((pkg (find (lambda (pkg) (string=? (stackage-package-name pkg) name))
+                   pkgs-info)))
+    (stackage-package-version pkg)))
+
+
+;;;
+;;; Importer entry point
+;;;
+
+(define (hackage-name-version name version)
+  (and version (string-append  name "@" version)))
+
+(define* (stackage->guix-package package-name ; upstream name
+                                 #:key
+                                 (include-test-dependencies? #t)
+                                 (lts-version "")
+                                 (packages-info
+                                  (lts-info-packages
+                                   (stackage-lts-info-fetch lts-version))))
+  "Fetch Cabal file for PACKAGE-NAME from hackage.haskell.org.  The retrieved
+vesion corresponds to the version of PACKAGE-NAME specified in the LTS-VERSION
+release at stackage.org.  Return the `package' S-expression corresponding to
+that package, or #f on failure.  PACKAGES-INFO is the alist with the packages
+included in the Stackage LTS release."
+  (let* ((version (lts-package-version packages-info package-name))
+         (name-version (hackage-name-version package-name version)))
+    (if name-version
+        (hackage->guix-package name-version
+                               #:include-test-dependencies?
+                               include-test-dependencies?)
+        (leave (_ "package not found: ~A~%") package-name))))
+
+
+;;;
+;;; Updater
+;;;
+
+(define latest-lts-release
+  (let ((pkgs-info (mlambda () (lts-info-packages (stackage-lts-info-fetch)))))
+    (lambda* (package)
+      "Return an <upstream-source> for the latest Stackage LTS release of
+PACKAGE or #f it the package is not inlucded in the Stackage LTS release."
+      (let* ((hackage-name (guix-package->hackage-name package))
+             (version (lts-package-version (pkgs-info) hackage-name))
+             (name-version (hackage-name-version hackage-name version)))
+        (match (and=> name-version hackage-fetch)
+          (#f (format (current-error-port)
+                      "warning: failed to parse ~a~%"
+                      (hackage-cabal-url hackage-name))
+              #f)
+          (_ (let ((url (hackage-source-url hackage-name version)))
+               (upstream-source
+                (package (package-name package))
+                (version version)
+                (urls (list url))))))))))
+
+(define %stackage-updater
+  (upstream-updater
+   (name 'stackage)
+   (description "Updater for Stackage LTS packages")
+   (pred hackage-package?)
+   (latest latest-lts-release)))
+
+;;; stackage.scm ends here
diff --git a/guix/scripts/import.scm b/guix/scripts/import.scm
index 4d07e0fd69..8c2f705738 100644
--- a/guix/scripts/import.scm
+++ b/guix/scripts/import.scm
@@ -73,7 +73,8 @@ rather than \\n."
 ;;; Entry point.
 ;;;
 
-(define importers '("gnu" "nix" "pypi" "cpan" "hackage" "elpa" "gem" "cran" "crate"))
+(define importers '("gnu" "nix" "pypi" "cpan" "hackage" "stackage" "elpa" "gem"
+                    "cran" "crate"))
 
 (define (resolve-importer name)
   (let ((module (resolve-interface
diff --git a/guix/scripts/import/stackage.scm b/guix/scripts/import/stackage.scm
new file mode 100644
index 0000000000..cf47bff259
--- /dev/null
+++ b/guix/scripts/import/stackage.scm
@@ -0,0 +1,115 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 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 stackage)
+  #:use-module (guix ui)
+  #:use-module (guix utils)
+  #:use-module (guix packages)
+  #:use-module (guix scripts)
+  #:use-module (guix import stackage)
+  #: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-stackage))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  `((lts-version . "")
+    (include-test-dependencies? . #t)))
+
+(define (show-help)
+  (display (_ "Usage: guix import stackage PACKAGE-NAME
+Import and convert the LTS Stackage package for PACKAGE-NAME.\n"))
+  (display (_ "
+  -r VERSION, --lts-version=VERSION
+                               specify the LTS version to use"))
+  (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 stackage")))
+         (option '(#\t "no-test-dependencies") #f #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'include-test-dependencies? #f
+                               (alist-delete 'include-test-dependencies?
+                                             result))))
+         (option '(#\r "lts-version") #t #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'lts-version arg
+                               (alist-delete 'lts-version
+                                             result))))
+         %standard-import-options))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-import-stackage . 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 (stackage->guix-package
+                    package-name
+                    #:include-test-dependencies?
+                    (assoc-ref opts 'include-test-dependencies?)
+                    #:lts-version (assoc-ref opts 'lts-version))))
+         (unless sexp
+           (leave (_ "failed to download cabal file for package '~a'~%")
+                  package-name))
+         sexp))
+      (()
+       (leave (_ "too few arguments~%")))
+      ((many ...)
+       (leave (_ "too many arguments~%"))))))
+
+;;; stackage.scm ends here
diff --git a/guix/scripts/refresh.scm b/guix/scripts/refresh.scm
index 0dd7eee974..4d3c695aaf 100644
--- a/guix/scripts/refresh.scm
+++ b/guix/scripts/refresh.scm
@@ -205,6 +205,7 @@ unavailable optional dependencies such as Guile-JSON."
                  %elpa-updater
                  %cran-updater
                  %bioconductor-updater
+                 ((guix import stackage) => %stackage-updater)
                  %hackage-updater
                  ((guix import cpan) => %cpan-updater)
                  ((guix import pypi) => %pypi-updater)