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.

2 files changed, 142 insertions, 1 deletions

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