Merge branch 'master' into core-updates

14 files changed, 471 insertions, 126 deletions

diff --git a/guix/base64.scm b/guix/base64.scm
index f7f7f5f4e1..e4d2ec589b 100644
--- a/guix/base64.scm
+++ b/guix/base64.scm
@@ -4,6 +4,8 @@
 ;; (guix base64) by Nikita Karetnikov <nikita@karetnikov.org> on
 ;; February 12, 2014.
 ;;
+;; Some optimizations made by Ludovic Courtès <ludo@gnu.org>, 2015.
+;;
 ;; Copyright © 2009, 2010 Göran Weinholt <goran@weinholt.se>
 ;;
 ;; This program is free software: you can redistribute it and/or modify
@@ -33,7 +35,23 @@
           (only (srfi :13 strings)
                 string-index
                 string-prefix? string-suffix?
-                string-concatenate string-trim-both))
+                string-concatenate string-trim-both)
+          (only (guile) ash logior))
+
+
+  (define-syntax define-alias
+    (syntax-rules ()
+      ((_ new old)
+       (define-syntax new (identifier-syntax old)))))
+
+  ;; Force the use of Guile's own primitives to avoid the overhead of its 'fx'
+  ;; procedures.
+  (define-alias fxbit-field bitwise-bit-field)
+  (define-alias fxarithmetic-shift ash)
+  (define-alias fxarithmetic-shift-left ash)
+  (define-alias fxand logand)
+  (define-alias fxior logior)
+  (define-alias fxxor logxor)
 
   (define base64-alphabet
     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
@@ -209,4 +227,4 @@
                       line-length #f base64-alphabet port)
        (display (string-append "\n-----END " type "-----\n") port))
       ((port type bv)
-       (put-delimited-base64 port type bv 76)))))
\ No newline at end of file
+       (put-delimited-base64 port type bv 76)))))
diff --git a/guix/derivations.scm b/guix/derivations.scm
index 69cef1a4cd..ec438e833c 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -58,9 +58,11 @@
             derivation-input-output-paths
 
             derivation-name
+            derivation-output-names
             fixed-output-derivation?
             offloadable-derivation?
             substitutable-derivation?
+            substitution-oracle
             derivation-hash
 
             read-derivation
@@ -135,6 +137,12 @@
   (let ((base (store-path-package-name (derivation-file-name drv))))
     (string-drop-right base 4)))
 
+(define (derivation-output-names drv)
+  "Return the names of the outputs of DRV."
+  (match (derivation-outputs drv)
+    (((names . _) ...)
+     names)))
+
 (define (fixed-output-derivation? drv)
   "Return #t if DRV is a fixed-output derivation, such as the result of a
 download with a fixed hash (aka. `fetchurl')."
@@ -177,41 +185,52 @@ download with a fixed hash (aka. `fetchurl')."
   ;; synonymous, see <http://bugs.gnu.org/18747>.
   offloadable-derivation?)
 
+(define (derivation-output-paths drv sub-drvs)
+  "Return the output paths of outputs SUB-DRVS of DRV."
+  (match drv
+    (($ <derivation> outputs)
+     (map (lambda (sub-drv)
+            (derivation-output-path (assoc-ref outputs sub-drv)))
+          sub-drvs))))
+
+(define* (substitution-oracle store drv)
+  "Return a one-argument procedure that, when passed a store file name,
+returns #t if it's substitutable and #f otherwise.  The returned procedure
+knows about all substitutes for all the derivations listed in DRV and their
+prerequisites.
+
+Creating a single oracle (thus making a single 'substitutable-paths' call) and
+reusing it is much more efficient than calling 'has-substitutes?' or similar
+repeatedly, because it avoids the costs associated with launching the
+substituter many times."
+  (let* ((paths (delete-duplicates
+                 (fold (lambda (drv result)
+                         (let ((self (match (derivation->output-paths drv)
+                                       (((names . paths) ...)
+                                        paths)))
+                               (deps (append-map derivation-input-output-paths
+                                                 (derivation-prerequisites
+                                                  drv))))
+                           (append self deps result)))
+                       '()
+                       drv)))
+         (subst (substitutable-paths store paths)))
+    (cut member <> subst)))
+
 (define* (derivation-prerequisites-to-build store drv
                                             #:key
                                             (outputs
-                                             (map
-                                              car
-                                              (derivation-outputs drv)))
-                                            (use-substitutes? #t))
+                                             (derivation-output-names drv))
+                                            (substitutable?
+                                             (substitution-oracle store
+                                                                  (list drv))))
   "Return two values: the list of derivation-inputs required to build the
 OUTPUTS of DRV and not already available in STORE, recursively, and the list
-of required store paths that can be substituted.  When USE-SUBSTITUTES? is #f,
-that second value is the empty list."
-  (define (derivation-output-paths drv sub-drvs)
-    (match drv
-      (($ <derivation> outputs)
-       (map (lambda (sub-drv)
-              (derivation-output-path (assoc-ref outputs sub-drv)))
-            sub-drvs))))
-
+of required store paths that can be substituted.  SUBSTITUTABLE? must be a
+one-argument procedure similar to that returned by 'substitution-oracle'."
   (define built?
     (cut valid-path? store <>))
 
-  (define substitutable?
-    ;; Return true if the given path is substitutable.  Call
-    ;; `substitutable-paths' upfront, to benefit from parallelism in the
-    ;; substituter.
-    (if use-substitutes?
-        (let ((s (substitutable-paths store
-                                      (append
-                                       (derivation-output-paths drv outputs)
-                                       (append-map
-                                        derivation-input-output-paths
-                                        (derivation-prerequisites drv))))))
-          (cut member <> s))
-        (const #f)))
-
   (define input-built?
     (compose (cut any built? <>) derivation-input-output-paths))
 
@@ -844,7 +863,7 @@ recursively."
                                                        replacements))))
                                     (derivation-builder-environment-vars drv))
                     #:inputs (append (map list sources) inputs)
-                    #:outputs (map car (derivation-outputs drv))
+                    #:outputs (derivation-output-names drv)
                     #:hash (match (derivation-outputs drv)
                              ((($ <derivation-output> _ algo hash))
                               hash)
diff --git a/guix/hash.scm b/guix/hash.scm
index fb85f47586..593c2e1aee 100644
--- a/guix/hash.scm
+++ b/guix/hash.scm
@@ -26,6 +26,7 @@
   #:export (sha256
             open-sha256-port
             port-sha256
+            file-sha256
             open-sha256-input-port))
 
 ;;; Commentary:
@@ -129,6 +130,10 @@ output port."
     (close-port out)
     (get)))
 
+(define (file-sha256 file)
+  "Return the SHA256 hash (a bytevector) of FILE."
+  (call-with-input-file file port-sha256))
+
 (define (open-sha256-input-port port)
   "Return an input port that wraps PORT and a thunk to get the hash of all the
 data read from PORT.  The thunk always returns the same value."
diff --git a/guix/import/cpan.scm b/guix/import/cpan.scm
new file mode 100644
index 0000000000..5f4602a8d2
--- /dev/null
+++ b/guix/import/cpan.scm
@@ -0,0 +1,167 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
+;;;
+;;; 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 cpan)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
+  #:use-module (srfi srfi-1)
+  #:use-module (json)
+  #:use-module (guix hash)
+  #:use-module (guix store)
+  #:use-module (guix base32)
+  #:use-module ((guix download) #:select (download-to-store))
+  #:use-module (guix import utils)
+  #:use-module (guix import json)
+  #:export (cpan->guix-package))
+
+;;; Commentary:
+;;;
+;;; Generate a package declaration template for the latest version of a CPAN
+;;; module, using meta-data from metacpan.org.
+;;;
+;;; Code:
+
+(define string->license
+  (match-lambda
+   ;; List of valid values from https://metacpan.org/pod/CPAN::Meta::Spec.
+   ;; Some licenses are excluded based on their absense from (guix licenses).
+   ("agpl_3" 'agpl3)
+   ;; apache_1_1
+   ("apache_2_0" 'asl2.0)
+   ;; artistic_1_0
+   ;; artistic_2_0
+   ("bsd" 'bsd-3)
+   ("freebsd" 'bsd-2)
+   ;; gfdl_1_2
+   ("gfdl_1_3" 'fdl1.3+)
+   ("gpl_1" 'gpl1)
+   ("gpl_2" 'gpl2)
+   ("gpl_3" 'gpl3)
+   ("lgpl_2_1" 'lgpl2.1)
+   ("lgpl_3_0" 'lgpl3)
+   ("mit" 'x11)
+   ;; mozilla_1_0
+   ("mozilla_1_1" 'mpl1.1)
+   ("openssl" 'openssl)
+   ("perl_5" 'gpl1+)                    ;and Artistic 1
+   ("qpl_1_0" 'qpl)
+   ;; ssleay
+   ;; sun
+   ("zlib" 'zlib)
+   ((x) (string->license x))
+   ((lst ...) `(list ,@(map string->license lst)))
+   (_ #f)))
+
+(define (module->name module)
+  "Transform a 'module' name into a 'release' name"
+  (regexp-substitute/global #f "::" module 'pre "-" 'post))
+
+(define (cpan-fetch module)
+  "Return an alist representation of the CPAN metadata for the perl module MODULE,
+or #f on failure.  MODULE should be e.g. \"Test::Script\""
+  ;; This API always returns the latest release of the module.
+  (json-fetch (string-append "http://api.metacpan.org/release/"
+                             ;; XXX: The 'release' api requires the "release"
+                             ;; name of the package.  This substitution seems
+                             ;; reasonably consistent across packages.
+                             (module->name module))))
+
+(define (cpan-home name)
+  (string-append "http://search.cpan.org/dist/" name))
+
+(define (cpan-module->sexp meta)
+  "Return the `package' s-expression for a CPAN module from the metadata in
+META."
+  (define name
+    (assoc-ref meta "distribution"))
+
+  (define (guix-name name)
+    (if (string-prefix? "perl-" name)
+        (string-downcase name)
+        (string-append "perl-" (string-downcase name))))
+
+  (define version
+    (assoc-ref meta "version"))
+
+  (define (convert-inputs phases)
+    ;; Convert phase dependencies into a list of name/variable pairs.
+    (match (flatten
+            (map (lambda (ph)
+                   (filter-map (lambda (t)
+                                 (assoc-ref* meta "metadata" "prereqs" ph t))
+                               '("requires" "recommends" "suggests")))
+                 phases))
+      (#f
+       '())
+      ((inputs ...)
+       (delete-duplicates
+        ;; Listed dependencies may include core modules.  Filter those out.
+        (filter-map (match-lambda
+                     ((or (module . "0") ("perl" . _))
+                      ;; TODO: A stronger test might to run MODULE through
+                      ;; `corelist' from our perl package.  This current test
+                      ;; seems to be only a loose convention.
+                      #f)
+                     ((module . _)
+                      (let ((name (guix-name (module->name module))))
+                        (list name
+                              (list 'unquote (string->symbol name))))))
+                    inputs)))))
+
+  (define (maybe-inputs guix-name inputs)
+    (match inputs
+      (()
+       '())
+      ((inputs ...)
+       (list (list guix-name
+                   (list 'quasiquote inputs))))))
+
+  (define source-url
+    (assoc-ref meta "download_url"))
+
+  (let ((tarball (with-store store
+                   (download-to-store store source-url))))
+    `(package
+       (name ,(guix-name name))
+       (version ,version)
+       (source (origin
+                 (method url-fetch)
+                 (uri (string-append ,@(factorize-uri source-url version)))
+                 (sha256
+                  (base32
+                   ,(bytevector->nix-base32-string (file-sha256 tarball))))))
+       (build-system perl-build-system)
+       ,@(maybe-inputs 'native-inputs
+                       ;; "runtime" and "test" may also be needed here.  See
+                       ;; https://metacpan.org/pod/CPAN::Meta::Spec#Phases,
+                       ;; which says they are required during building.  We
+                       ;; have not yet had a need for cross-compiled perl
+                       ;; modules, however, so we leave them out.
+                       (convert-inputs '("configure" "build")))
+       ,@(maybe-inputs 'inputs
+                       (convert-inputs '("runtime")))
+       (home-page ,(string-append "http://search.cpan.org/dist/" name))
+       (synopsis ,(assoc-ref meta "abstract"))
+       (description fill-in-yourself!)
+       (license ,(string->license (assoc-ref meta "license"))))))
+
+(define (cpan->guix-package module-name)
+  "Fetch the metadata for PACKAGE-NAME from metacpan.org, and return the
+`package' s-expression corresponding to that package, or #f on failure."
+  (let ((module-meta (cpan-fetch module-name)))
+    (and=> module-meta cpan-module->sexp)))
diff --git a/guix/import/gnu.scm b/guix/import/gnu.scm
index 1947f489fb..7160fcf7ba 100644
--- a/guix/import/gnu.scm
+++ b/guix/import/gnu.scm
@@ -18,6 +18,7 @@
 
 (define-module (guix import gnu)
   #:use-module (guix gnu-maintenance)
+  #:use-module (guix import utils)
   #:use-module (guix utils)
   #:use-module (guix store)
   #:use-module (guix hash)
@@ -38,10 +39,6 @@
 ;;;
 ;;; Code:
 
-(define (file-sha256 file)
-  "Return the SHA256 hash of FILE as a bytevector."
-  (call-with-input-file file port-sha256))
-
 (define (qualified-url url)
   "Return a fully-qualified URL based on URL."
   (if (string-prefix? "/" url)
@@ -102,7 +99,7 @@ details.)"
      (let ((version (gnu-release-version release)))
        (match (find-packages (regexp-quote name))
          ((info . _)
-          (gnu-package->sexp info release))
+          (gnu-package->sexp info release #:key-download key-download))
          (()
           (raise (condition
                   (&message
diff --git a/guix/import/json.scm b/guix/import/json.scm
new file mode 100644
index 0000000000..c3092a5a9d
--- /dev/null
+++ b/guix/import/json.scm
@@ -0,0 +1,32 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 David Thompson <davet@gnu.org>
+;;; Copyright © 2015 Eric Bavier <bavier@member.fsf.org>
+;;;
+;;; 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 json)
+  #:use-module (json)
+  #:use-module (guix utils)
+  #:use-module (guix import utils)
+  #:export (json-fetch))
+
+(define (json-fetch url)
+  "Return an alist representation of the JSON resource URL, or #f on failure."
+  (call-with-temporary-output-file
+   (lambda (temp port)
+     (and (url-fetch url temp)
+          (hash-table->alist
+           (call-with-input-file temp json->scm))))))
diff --git a/guix/import/pypi.scm b/guix/import/pypi.scm
index 88f4a8e896..8567cad79c 100644
--- a/guix/import/pypi.scm
+++ b/guix/import/pypi.scm
@@ -27,40 +27,15 @@
   #:use-module (web uri)
   #:use-module (guix utils)
   #:use-module (guix import utils)
+  #:use-module (guix import json)
   #:use-module (guix base32)
   #:use-module (guix hash)
   #:use-module (guix packages)
   #:use-module (guix licenses)
   #:use-module (guix build-system python)
-  #:use-module ((guix build download) #:prefix build:)
   #:use-module (gnu packages python)
   #:export (pypi->guix-package))
 
-(define (hash-table->alist table)
-  "Return an alist represenation of TABLE."
-  (map (match-lambda
-        ((key . (lst ...))
-         (cons key
-               (map (lambda (x)
-                      (if (hash-table? x)
-                          (hash-table->alist x)
-                          x))
-                    lst)))
-        ((key . (? hash-table? table))
-         (cons key (hash-table->alist table)))
-        (pair pair))
-       (hash-map->list cons table)))
-
-(define (flatten lst)
-  "Return a list that recursively concatenates all sub-lists of LIST."
-  (fold-right
-   (match-lambda*
-    (((sub-list ...) memo)
-     (append (flatten sub-list) memo))
-    ((elem memo)
-     (cons elem memo)))
-   '() lst))
-
 (define (join lst delimiter)
   "Return a list that contains the elements of LST, each separated by
 DELIMETER."
@@ -71,13 +46,6 @@ DELIMETER."
     ((elem . rest)
      (cons* elem delimiter (join rest delimiter)))))
 
-(define (assoc-ref* alist key . rest)
-  "Return the value for KEY from ALIST.  For each additional key specified,
-recursively apply the procedure to the sub-list."
-  (if (null? rest)
-      (assoc-ref alist key)
-      (apply assoc-ref* (assoc-ref alist key) rest)))
-
 (define string->license
   (match-lambda
    ("GNU LGPL" lgpl2.0)
@@ -88,19 +56,6 @@ recursively apply the procedure to the sub-list."
    ("Apache License, Version 2.0" asl2.0)
    (_ #f)))
 
-(define (url-fetch url file-name)
-  "Save the contents of URL to FILE-NAME.  Return #f on failure."
-  (parameterize ((current-output-port (current-error-port)))
-    (build:url-fetch url file-name)))
-
-(define (json-fetch url)
-  "Return an alist representation of the JSON resource URL, or #f on failure."
-  (call-with-temporary-output-file
-   (lambda (temp port)
-     (and (url-fetch url temp)
-          (hash-table->alist
-           (call-with-input-file temp json->scm))))))
-
 (define (pypi-fetch name)
   "Return an alist representation of the PyPI metadata for the package NAME,
 or #f on failure."
diff --git a/guix/import/utils.scm b/guix/import/utils.scm
index 062cfc54f3..969491d28d 100644
--- a/guix/import/utils.scm
+++ b/guix/import/utils.scm
@@ -20,7 +20,16 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 regex)
   #:use-module (srfi srfi-1)
-  #:export (factorize-uri))
+  #:use-module (guix hash)
+  #:use-module (guix utils)
+  #:use-module ((guix build download) #:prefix build:)
+  #:export (factorize-uri
+
+            hash-table->alist
+            flatten
+            assoc-ref*
+
+            url-fetch))
 
 (define (factorize-uri uri version)
   "Factorize URI, a package tarball URI as a string, such that any occurrences
@@ -49,3 +58,40 @@ of the string VERSION is replaced by the symbol 'version."
                            result))))
                '()
                indices))))))
+
+(define (hash-table->alist table)
+  "Return an alist represenation of TABLE."
+  (map (match-lambda
+        ((key . (lst ...))
+         (cons key
+               (map (lambda (x)
+                      (if (hash-table? x)
+                          (hash-table->alist x)
+                          x))
+                    lst)))
+        ((key . (? hash-table? table))
+         (cons key (hash-table->alist table)))
+        (pair pair))
+       (hash-map->list cons table)))
+
+(define (flatten lst)
+  "Return a list that recursively concatenates all sub-lists of LST."
+  (fold-right
+   (match-lambda*
+    (((sub-list ...) memo)
+     (append (flatten sub-list) memo))
+    ((elem memo)
+     (cons elem memo)))
+   '() lst))
+
+(define (assoc-ref* alist key . rest)
+  "Return the value for KEY from ALIST.  For each additional key specified,
+recursively apply the procedure to the sub-list."
+  (if (null? rest)
+      (assoc-ref alist key)
+      (apply assoc-ref* (assoc-ref alist key) rest)))
+
+(define (url-fetch url file-name)
+  "Save the contents of URL to FILE-NAME.  Return #f on failure."
+  (parameterize ((current-output-port (current-error-port)))
+    (build:url-fetch url file-name)))
diff --git a/guix/records.scm b/guix/records.scm
index 93c52f0ffa..e7b86af9aa 100644
--- a/guix/records.scm
+++ b/guix/records.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -267,15 +267,12 @@ PORT, according to FIELDS.  FIELDS must be a list of field name/getter pairs."
        (format port "~a: ~a~%" field (get object))
        (loop rest)))))
 
-(define %recutils-field-rx
-  (make-regexp "^([[:graph:]]+): (.*)$"))
-
-(define %recutils-comment-rx
-  ;; info "(recutils) Comments"
-  (make-regexp "^#"))
-
-(define %recutils-plus-rx
-  (make-regexp "^\\+ ?(.*)$"))
+(define %recutils-field-charset
+  ;; Valid characters starting a recutils field.
+  ;; info "(recutils) Fields"
+  (char-set-union char-set:upper-case
+                  char-set:lower-case
+                  (char-set #\%)))
 
 (define (recutils->alist port)
   "Read a recutils-style record from PORT and return it as a list of key/value
@@ -288,25 +285,29 @@ pairs.  Stop upon an empty line (after consuming it) or EOF."
            (if (null? result)
                (loop (read-line port) result)     ; leading space: ignore it
                (reverse result)))                 ; end-of-record marker
-          ((regexp-exec %recutils-comment-rx line)
-           (loop (read-line port) result))
-          ((regexp-exec %recutils-plus-rx line)
-           =>
-           (lambda (m)
-             (match result
-               (((field . value) rest ...)
-                (loop (read-line port)
-                      `((,field . ,(string-append value "\n"
-                                                  (match:substring m 1)))
-                        ,@rest))))))
-          ((regexp-exec %recutils-field-rx line)
-           =>
-           (lambda (match)
-             (loop (read-line port)
-                   (alist-cons (match:substring match 1)
-                               (match:substring match 2)
-                               result))))
           (else
-           (error "unmatched line" line)))))
+           ;; Now check the first character of LINE, since that's what the
+           ;; recutils manual says is enough.
+           (let ((first (string-ref line 0)))
+             (cond
+              ((char-set-contains? %recutils-field-charset first)
+               (let* ((colon (string-index line #\:))
+                      (field (string-take line colon))
+                      (value (string-trim (string-drop line (+ 1 colon)))))
+                 (loop (read-line port)
+                       (alist-cons field value result))))
+              ((eqv? first #\#)                   ;info "(recutils) Comments"
+               (loop (read-line port) result))
+              ((eqv? first #\+)                   ;info "(recutils) Fields"
+               (let ((new-line (if (string-prefix? "+ " line)
+                                   (string-drop line 2)
+                                   (string-drop line 1))))
+                (match result
+                  (((field . value) rest ...)
+                   (loop (read-line port)
+                         `((,field . ,(string-append value "\n" new-line))
+                           ,@rest))))))
+              (else
+               (error "unmatched line" line))))))))
 
 ;;; records.scm ends here
diff --git a/guix/scripts/import.scm b/guix/scripts/import.scm
index 86ef05bc2c..7e75c10b3e 100644
--- a/guix/scripts/import.scm
+++ b/guix/scripts/import.scm
@@ -73,7 +73,7 @@ rather than \\n."
 ;;; Entry point.
 ;;;
 
-(define importers '("gnu" "nix" "pypi"))
+(define importers '("gnu" "nix" "pypi" "cpan"))
 
 (define (resolve-importer name)
   (let ((module (resolve-interface
diff --git a/guix/scripts/import/cpan.scm b/guix/scripts/import/cpan.scm
new file mode 100644
index 0000000000..1f4dedf23f
--- /dev/null
+++ b/guix/scripts/import/cpan.scm
@@ -0,0 +1,91 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
+;;;
+;;; 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 cpan)
+  #:use-module (guix ui)
+  #:use-module (guix utils)
+  #:use-module (guix import cpan)
+  #: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-cpan))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  '())
+
+(define (show-help)
+  (display (_ "Usage: guix import cpan PACKAGE-NAME
+Import and convert the CPAN package for PACKAGE-NAME.\n"))
+  (display (_ "
+  -h, --help             display this help and exit"))
+  (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 cpan")))
+         %standard-import-options))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-import-cpan . 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 (cpan->guix-package package-name)))
+         (unless sexp
+           (leave (_ "failed to download meta-data for package '~a'~%")
+                  package-name))
+         sexp))
+      (()
+       (leave (_ "too few arguments~%")))
+      ((many ...)
+       (leave (_ "too many arguments~%"))))))
diff --git a/guix/scripts/substitute-binary.scm b/guix/scripts/substitute-binary.scm
index 9c96411630..09b917fdf6 100755
--- a/guix/scripts/substitute-binary.scm
+++ b/guix/scripts/substitute-binary.scm
@@ -241,7 +241,7 @@ failure."
     ((version _ sig)
      (let ((maybe-number (string->number version)))
        (cond ((not (number? maybe-number))
-              (leave (_ "signature version must be a number: ~a~%")
+              (leave (_ "signature version must be a number: ~s~%")
                      version))
              ;; Currently, there are no other versions.
              ((not (= 1 maybe-number))
@@ -313,18 +313,15 @@ No authentication and authorization checks are performed here!"
                      "References" "Deriver" "System"
                      "Signature"))))
 
-(define %signature-line-rx
-  ;; Regexp matching a signature line in a narinfo.
-  (make-regexp "(.+)^[[:blank:]]*Signature:[[:blank:]].+$"))
-
 (define (narinfo-sha256 narinfo)
   "Return the sha256 hash of NARINFO as a bytevector, or #f if NARINFO lacks a
 'Signature' field."
   (let ((contents (narinfo-contents narinfo)))
-    (match (regexp-exec %signature-line-rx contents)
+    (match (string-contains contents "Signature:")
       (#f #f)
-      ((= (cut match:substring <> 1) above-signature)
-       (sha256 (string->utf8 above-signature))))))
+      (index
+       (let ((above-signature (string-take contents index)))
+         (sha256 (string->utf8 above-signature)))))))
 
 (define* (assert-valid-narinfo narinfo
                                #:optional (acl (current-acl))
diff --git a/guix/tests.scm b/guix/tests.scm
index 82ae7e2084..36341cb4cc 100644
--- a/guix/tests.scm
+++ b/guix/tests.scm
@@ -27,6 +27,7 @@
   #:export (open-connection-for-tests
             random-text
             random-bytevector
+            mock
             with-derivation-narinfo
             dummy-package))
 
@@ -70,6 +71,16 @@
             (loop (1+ i)))
           bv))))
 
+(define-syntax-rule (mock (module proc replacement) body ...)
+  "Within BODY, replace the definition of PROC from MODULE with the definition
+given by REPLACEMENT."
+  (let* ((m (resolve-module 'module))
+         (original (module-ref m 'proc)))
+    (dynamic-wind
+      (lambda () (module-set! m 'proc replacement))
+      (lambda () body ...)
+      (lambda () (module-set! m 'proc original)))))
+
 
 ;;;
 ;;; Narinfo files, as used by the substituter.
diff --git a/guix/ui.scm b/guix/ui.scm
index c77e04172e..5bd4d1f8c2 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
 ;;; Copyright © 2014 Alex Kost <alezost@gmail.com>
@@ -299,21 +299,27 @@ error."
 derivations listed in DRV.  Return #t if there's something to build, #f
 otherwise.  When USE-SUBSTITUTES?, check and report what is prerequisites are
 available for download."
+  (define substitutable?
+    ;; Call 'substitutation-oracle' upfront so we don't end up launching the
+    ;; substituter many times.  This makes a big difference, especially when
+    ;; DRV is a long list as is the case with 'guix environment'.
+    (if use-substitutes?
+        (substitution-oracle store drv)
+        (const #f)))
+
   (define (built-or-substitutable? drv)
     (let ((out (derivation->output-path drv)))
       ;; If DRV has zero outputs, OUT is #f.
       (or (not out)
           (or (valid-path? store out)
-              (and use-substitutes?
-                   (has-substitutes? store out))))))
+              (substitutable? out)))))
 
   (let*-values (((build download)
                  (fold2 (lambda (drv build download)
                           (let-values (((b d)
                                         (derivation-prerequisites-to-build
                                          store drv
-                                         #:use-substitutes?
-                                         use-substitutes?)))
+                                         #:substitutable? substitutable?)))
                             (values (append b build)
                                     (append d download))))
                         '() '()