Merge branch 'master' into core-updates

9 files changed, 733 insertions, 89 deletions

diff --git a/guix/build-system/cargo.scm b/guix/build-system/cargo.scm
index c637fbb162..4a1eb0cfa0 100644
--- a/guix/build-system/cargo.scm
+++ b/guix/build-system/cargo.scm
@@ -43,17 +43,11 @@
 to NAME and VERSION."
   (string-append crate-url name "/" version "/download"))
 
-(define (default-cargo)
-  "Return the default Cargo package."
+(define (default-rust)
+  "Return the default Rust package."
   ;; Lazily resolve the binding to avoid a circular dependency.
   (let ((rust (resolve-interface '(gnu packages rust))))
-    (module-ref rust 'cargo)))
-
-(define (default-rustc)
-  "Return the default Rustc package."
-  ;; Lazily resolve the binding to avoid a circular dependency.
-  (let ((rust (resolve-interface '(gnu packages rust))))
-    (module-ref rust 'rustc)))
+    (module-ref rust 'rust)))
 
 (define %cargo-build-system-modules
   ;; Build-side modules imported by default.
@@ -115,14 +109,13 @@ to NAME and VERSION."
 
 (define* (lower name
                 #:key source inputs native-inputs outputs system target
-                (cargo (default-cargo))
-                (rustc (default-rustc))
+                (rust (default-rust))
                 #:allow-other-keys
                 #:rest arguments)
   "Return a bag for NAME."
 
   (define private-keywords
-    '(#:source #:target #:cargo #:rustc #:inputs #:native-inputs #:outputs))
+    '(#:source #:target #:rust #:inputs #:native-inputs #:outputs))
 
   (and (not target) ;; TODO: support cross-compilation
        (bag
@@ -136,8 +129,8 @@ to NAME and VERSION."
 
                         ;; Keep the standard inputs of 'gnu-build-system'
                         ,@(standard-packages)))
-         (build-inputs `(("cargo" ,cargo)
-                         ("rustc" ,rustc)
+         (build-inputs `(("cargo" ,rust "cargo")
+                         ("rustc" ,rust)
                          ,@native-inputs))
          (outputs outputs)
          (build cargo-build)
diff --git a/guix/build/union.scm b/guix/build/union.scm
index d46b750035..1179f1234b 100644
--- a/guix/build/union.scm
+++ b/guix/build/union.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2017 Huang Ying <huang.ying.caritas@gmail.com>
 ;;;
@@ -25,7 +25,9 @@
   #:use-module (srfi srfi-26)
   #:use-module (rnrs bytevectors)
   #:use-module (rnrs io ports)
-  #:export (union-build))
+  #:export (union-build
+
+            warn-about-collision))
 
 ;;; Commentary:
 ;;;
@@ -76,14 +78,29 @@ identical, #f otherwise."
                                    (or (eof-object? n1)
                                        (loop))))))))))))))
 
+(define (warn-about-collision files)
+  "Handle the collision among FILES by emitting a warning and choosing the
+first one of THEM."
+  (format (current-error-port)
+          "~%warning: collision encountered:~%~{  ~a~%~}"
+          files)
+  (let ((file (first files)))
+    (format (current-error-port) "warning: choosing ~a~%" file)
+    file))
+
 (define* (union-build output inputs
                       #:key (log-port (current-error-port))
                       (create-all-directories? #f)
-                      (symlink symlink))
+                      (symlink symlink)
+                      (resolve-collision warn-about-collision))
   "Build in the OUTPUT directory a symlink tree that is the union of all the
 INPUTS, using SYMLINK to create symlinks.  As a special case, if
 CREATE-ALL-DIRECTORIES?, creates the subdirectories in the output directory to
-make sure the caller can modify them later."
+make sure the caller can modify them later.
+
+When two or more regular files collide, call RESOLVE-COLLISION with the list
+of colliding files and use the one that it returns; or, if RESOLVE-COLLISION
+returns #f, skip the faulty file altogether."
 
   (define (symlink* input output)
     (format log-port "`~a' ~~> `~a'~%" input output)
@@ -92,17 +109,10 @@ make sure the caller can modify them later."
   (define (resolve-collisions output dirs files)
     (cond ((null? dirs)
            ;; The inputs are all files.
-           (format (current-error-port)
-                   "~%warning: collision encountered:~%~{~a~%~}"
-                   files)
-
-           (let ((file (first files)))
-             ;; TODO: Implement smarter strategies.
-             (format (current-error-port)
-                     "warning: arbitrarily choosing ~a~%"
-                     file)
-
-             (symlink* file output)))
+           (match (resolve-collision files)
+             (#f #f)
+             ((? string? file)
+              (symlink* file output))))
 
           (else
            ;; The inputs are a mixture of files and directories
diff --git a/guix/discovery.scm b/guix/discovery.scm
index 7b57579023..2b627d108e 100644
--- a/guix/discovery.scm
+++ b/guix/discovery.scm
@@ -17,7 +17,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix discovery)
-  #:use-module (guix ui)
+  #:use-module (guix i18n)
   #:use-module (guix modules)
   #:use-module (guix combinators)
   #:use-module (guix build syscalls)
@@ -25,7 +25,8 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 vlist)
   #:use-module (ice-9 ftw)
-  #:export (scheme-modules
+  #:export (scheme-files
+            scheme-modules
             fold-modules
             all-modules
             fold-module-public-variables))
@@ -85,13 +86,18 @@ DIRECTORY is not accessible."
                 (lambda args
                   (let ((errno (system-error-errno args)))
                     (unless (= errno ENOENT)
-                      (warning (G_ "cannot access `~a': ~a~%")
-                               directory (strerror errno)))
+                      (format (current-error-port) ;XXX
+                              (G_ "cannot access `~a': ~a~%")
+                              directory (strerror errno)))
                     '())))))
 
-(define* (scheme-modules directory #:optional sub-directory)
+(define* (scheme-modules directory #:optional sub-directory
+                         #:key (warn (const #f)))
   "Return the list of Scheme modules available under DIRECTORY.
-Optionally, narrow the search to SUB-DIRECTORY."
+Optionally, narrow the search to SUB-DIRECTORY.
+
+WARN is called when a module could not be loaded.  It is passed the module
+name and the exception key and arguments."
   (define prefix-len
     (string-length directory))
 
@@ -103,31 +109,32 @@ Optionally, narrow the search to SUB-DIRECTORY."
                       (resolve-interface module))
                     (lambda args
                       ;; Report the error, but keep going.
-                      (warn-about-load-error module args)
+                      (warn module args)
                       #f))))
               (scheme-files (if sub-directory
                                 (string-append directory "/" sub-directory)
                                 directory))))
 
-(define (fold-modules proc init path)
+(define* (fold-modules proc init path #:key (warn (const #f)))
   "Fold over all the Scheme modules present in PATH, a list of directories.
 Call (PROC MODULE RESULT) for each module that is found."
   (fold (lambda (spec result)
           (match spec
             ((? string? directory)
-             (fold proc result (scheme-modules directory)))
+             (fold proc result (scheme-modules directory #:warn warn)))
             ((directory . sub-directory)
              (fold proc result
-                   (scheme-modules directory sub-directory)))))
+                   (scheme-modules directory sub-directory
+                                   #:warn warn)))))
         '()
         path))
 
-(define (all-modules path)
+(define* (all-modules path #:key (warn (const #f)))
   "Return the list of package modules found in PATH, a list of directories to
 search.  Entries in PATH can be directory names (strings) or (DIRECTORY
 . SUB-DIRECTORY) pairs, in which case modules are searched for beneath
 SUB-DIRECTORY."
-  (fold-modules cons '() path))
+  (fold-modules cons '() path #:warn warn))
 
 (define (fold-module-public-variables proc init modules)
   "Call (PROC OBJECT RESULT) for each variable exported by one of MODULES,
diff --git a/guix/gexp.scm b/guix/gexp.scm
index 2deec253ff..bedb387edb 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -1258,7 +1258,8 @@ This yields an 'etc' directory containing these two files."
                           files))))))
 
 (define* (directory-union name things
-                          #:key (copy? #f) (quiet? #f))
+                          #:key (copy? #f) (quiet? #f)
+                          (resolve-collision 'warn-about-collision))
   "Return a directory that is the union of THINGS, where THINGS is a list of
 file-like objects denoting directories.  For example:
 
@@ -1266,6 +1267,10 @@ file-like objects denoting directories.  For example:
 
 yields a directory that is the union of the 'guile' and 'emacs' packages.
 
+Call RESOLVE-COLLISION when several files collide, passing it the list of
+colliding files.  RESOLVE-COLLISION must return the chosen file or #f, in
+which case the colliding entry is skipped altogether.
+
 When HARD-LINKS? is true, create hard links instead of symlinks.  When QUIET?
 is true, the derivation will not print anything."
   (define symlink
@@ -1289,12 +1294,16 @@ is true, the derivation will not print anything."
      (computed-file name
                     (with-imported-modules '((guix build union))
                       (gexp (begin
-                              (use-modules (guix build union))
+                              (use-modules (guix build union)
+                                           (srfi srfi-1)) ;for 'first' and 'last'
+
                               (union-build (ungexp output)
                                            '(ungexp things)
 
                                            #:log-port (ungexp log-port)
-                                           #:symlink (ungexp symlink)))))))))
+                                           #:symlink (ungexp symlink)
+                                           #:resolve-collision
+                                           (ungexp resolve-collision)))))))))
 
 
 ;;;
diff --git a/guix/git.scm b/guix/git.scm
index 103749d0e2..9e89cc0062 100644
--- a/guix/git.scm
+++ b/guix/git.scm
@@ -28,9 +28,11 @@
   #:use-module (rnrs bytevectors)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-35)
   #:export (%repository-cache-directory
+            update-cached-checkout
             latest-repository-commit))
 
 (define %repository-cache-directory
@@ -68,11 +70,6 @@ make sure no empty directory is left behind."
     (lambda _
       (false-if-exception (rmdir directory)))))
 
-(define (repository->head-sha1 repo)
-  "Return the sha1 of the HEAD commit in REPOSITORY as a string."
-  (let ((oid (reference-target (repository-head repo))))
-    (oid->string (commit-id (commit-lookup repo oid)))))
-
 (define (url+commit->name url sha1)
   "Return the string \"<REPO-NAME>-<SHA1:7>\" where REPO-NAME is the name of
 the git repository, extracted from URL and SHA1:7 the seven first digits
@@ -82,21 +79,9 @@ of SHA1 string."
     (last (string-split url #\/)) ".git" "")
    "-" (string-take sha1 7)))
 
-(define* (copy-to-store store cache-directory #:key url repository)
-  "Copy CACHE-DIRECTORY recursively to STORE.  URL and REPOSITORY are used to
-create the store directory name."
-  (define (dot-git? file stat)
-    (and (string=? (basename file) ".git")
-         (eq? 'directory (stat:type stat))))
-
-  (let* ((commit (repository->head-sha1 repository))
-         (name   (url+commit->name url commit)))
-    (values (add-to-store store name #t "sha256" cache-directory
-                          #:select? (negate dot-git?))
-            commit)))
-
 (define (switch-to-ref repository ref)
-  "Switch to REPOSITORY's branch, commit or tag specified by REF."
+  "Switch to REPOSITORY's branch, commit or tag specified by REF.  Return the
+OID (roughly the commit hash) corresponding to REF."
   (define obj
     (match ref
       (('branch . branch)
@@ -122,7 +107,38 @@ create the store directory name."
                                        (string-append "refs/tags/" tag))))
          (object-lookup repository oid)))))
 
-  (reset repository obj RESET_HARD))
+  (reset repository obj RESET_HARD)
+  (object-id obj))
+
+(define* (update-cached-checkout url
+                                 #:key
+                                 (ref '(branch . "origin/master"))
+                                 (cache-directory
+                                  (%repository-cache-directory)))
+  "Update the cached checkout of URL to REF in CACHE-DIRECTORY.  Return two
+values: the cache directory name, and the SHA1 commit (a string) corresponding
+to REF.
+
+REF is pair whose key is [branch | commit | tag] and value the associated
+data, respectively [<branch name> | <sha1> | <tag name>]."
+  (with-libgit2
+   (let* ((cache-dir     (url-cache-directory url cache-directory))
+          (cache-exists? (openable-repository? cache-dir))
+          (repository    (if cache-exists?
+                             (repository-open cache-dir)
+                             (clone* url cache-dir))))
+     ;; Only fetch remote if it has not been cloned just before.
+     (when cache-exists?
+       (remote-fetch (remote-lookup repository "origin")))
+     (let ((oid (switch-to-ref repository ref)))
+
+       ;; Reclaim file descriptors and memory mappings associated with
+       ;; REPOSITORY as soon as possible.
+       (when (module-defined? (resolve-interface '(git repository))
+                              'repository-close!)
+         (repository-close! repository))
+
+       (values cache-dir (oid->string oid))))))
 
 (define* (latest-repository-commit store url
                                    #:key
@@ -137,23 +153,16 @@ data, respectively [<branch name> | <sha1> | <tag name>].
 
 Git repositories are kept in the cache directory specified by
 %repository-cache-directory parameter."
-  (with-libgit2
-   (let* ((cache-dir     (url-cache-directory url cache-directory))
-          (cache-exists? (openable-repository? cache-dir))
-          (repository    (if cache-exists?
-                             (repository-open cache-dir)
-                             (clone* url cache-dir))))
-     ;; Only fetch remote if it has not been cloned just before.
-     (when cache-exists?
-       (remote-fetch (remote-lookup repository "origin")))
-     (switch-to-ref repository ref)
-
-     ;; Reclaim file descriptors and memory mappings associated with
-     ;; REPOSITORY as soon as possible.
-     (when (module-defined? (resolve-interface '(git repository))
-                            'repository-close!)
-       (repository-close! repository))
+  (define (dot-git? file stat)
+    (and (string=? (basename file) ".git")
+         (eq? 'directory (stat:type stat))))
 
-     (copy-to-store store cache-dir
-                    #:url url
-                    #:repository repository))))
+  (let*-values (((checkout commit)
+                 (update-cached-checkout url
+                                         #:ref ref
+                                         #:cache-directory cache-directory))
+                ((name)
+                 (url+commit->name url commit)))
+    (values (add-to-store store name #t "sha256" checkout
+                          #:select? (negate dot-git?))
+            commit)))
diff --git a/guix/modules.scm b/guix/modules.scm
index bf656bb241..65928f67f2 100644
--- a/guix/modules.scm
+++ b/guix/modules.scm
@@ -25,6 +25,7 @@
   #:use-module (ice-9 match)
   #:export (missing-dependency-error?
             missing-dependency-module
+            missing-dependency-search-path
 
             file-name->module-name
             module-name->file-name
@@ -47,7 +48,8 @@
 ;; The error corresponding to a missing module.
 (define-condition-type &missing-dependency-error &error
   missing-dependency-error?
-  (module  missing-dependency-module))
+  (module      missing-dependency-module)
+  (search-path missing-dependency-search-path))
 
 (define (colon-symbol? obj)
   "Return true if OBJ is a symbol that starts with a colon."
@@ -132,7 +134,8 @@ depends on."
          (module-file-dependencies file))
         (#f
          (raise (condition (&missing-dependency-error
-                            (module module))))))))
+                            (module module)
+                            (search-path load-path))))))))
 
 (define* (module-closure modules
                          #:key
diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index d8b80efe8e..4f519e6f33 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -194,15 +194,18 @@ denote ranges as interpreted by 'matching-generations'."
 
 (define* (build-and-use-profile store profile manifest
                                 #:key
+                                allow-collisions?
                                 bootstrap? use-substitutes?
                                 dry-run?)
   "Build a new generation of PROFILE, a file name, using the packages
-specified in MANIFEST, a manifest object."
+specified in MANIFEST, a manifest object.  When ALLOW-COLLISIONS? is true,
+do not treat collisions in MANIFEST as an error."
   (when (equal? profile %current-profile)
     (ensure-default-profile))
 
   (let* ((prof-drv (run-with-store store
                      (profile-derivation manifest
+                                         #:allow-collisions? allow-collisions?
                                          #:hooks (if bootstrap?
                                                      '()
                                                      %default-profile-hooks)
@@ -408,6 +411,8 @@ Install, remove, or upgrade packages in a single transaction.\n"))
   -p, --profile=PROFILE  use PROFILE instead of the user's default profile"))
   (newline)
   (display (G_ "
+      --allow-collisions do not treat collisions in the profile as an error"))
+  (display (G_ "
       --bootstrap        use the bootstrap Guile to build the profile"))
   (display (G_ "
       --verbose          produce verbose output"))
@@ -544,6 +549,10 @@ kind of search path~%")
                  (lambda (opt name arg result arg-handler)
                    (values (alist-cons 'verbose? #t result)
                            #f)))
+         (option '("allow-collisions") #f #f
+                 (lambda (opt name arg result arg-handler)
+                   (values (alist-cons 'allow-collisions? #t result)
+                           #f)))
          (option '(#\s "search") #t #f
                  (lambda (opt name arg result arg-handler)
                    (values (cons `(query search ,(or arg ""))
@@ -831,13 +840,15 @@ processed, #f otherwise."
   (let* ((user-module  (make-user-module '((guix profiles) (gnu))))
          (manifest     (load* file user-module))
          (bootstrap?   (assoc-ref opts 'bootstrap?))
-         (substitutes? (assoc-ref opts 'substitutes?)))
+         (substitutes? (assoc-ref opts 'substitutes?))
+         (allow-collisions? (assoc-ref opts 'allow-collisions?)))
     (if dry-run?
         (format #t (G_ "would install new manifest from '~a' with ~d entries~%")
                 file (length (manifest-entries manifest)))
         (format #t (G_ "installing new manifest from '~a' with ~d entries~%")
                 file (length (manifest-entries manifest))))
     (build-and-use-profile store profile manifest
+                           #:allow-collisions? allow-collisions?
                            #:bootstrap? bootstrap?
                            #:use-substitutes? substitutes?
                            #:dry-run? dry-run?)))
@@ -856,6 +867,7 @@ processed, #f otherwise."
   (define dry-run? (assoc-ref opts 'dry-run?))
   (define bootstrap? (assoc-ref opts 'bootstrap?))
   (define substitutes? (assoc-ref opts 'substitutes?))
+  (define allow-collisions? (assoc-ref opts 'allow-collisions?))
   (define profile  (or (assoc-ref opts 'profile) %current-profile))
   (define transform (options->transformation opts))
 
@@ -894,6 +906,7 @@ processed, #f otherwise."
       (show-manifest-transaction store manifest step3
                                  #:dry-run? dry-run?)
       (build-and-use-profile store profile new
+                             #:allow-collisions? allow-collisions?
                              #:bootstrap? bootstrap?
                              #:use-substitutes? substitutes?
                              #:dry-run? dry-run?))))
diff --git a/guix/self.scm b/guix/self.scm
new file mode 100644
index 0000000000..c9e4a4250e
--- /dev/null
+++ b/guix/self.scm
@@ -0,0 +1,599 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017, 2018 Ludovic Courtès <ludo@gnu.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 self)
+  #:use-module (guix config)
+  #:use-module (guix i18n)
+  #:use-module (guix modules)
+  #:use-module (guix gexp)
+  #:use-module (guix store)
+  #:use-module (guix monads)
+  #:use-module (guix discovery)
+  #:use-module (guix packages)
+  #:use-module (guix sets)
+  #:use-module (guix utils)
+  #:use-module (guix modules)
+  #:use-module (guix build utils)
+  #:use-module ((guix build compile) #:select (%lightweight-optimizations))
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (ice-9 match)
+  #:export (make-config.scm
+            compiled-guix
+            guix-derivation
+            reload-guix))
+
+
+;;;
+;;; Dependency handling.
+;;;
+
+(define* (false-if-wrong-guile package
+                               #:optional (guile-version (effective-version)))
+  "Return #f if PACKAGE depends on the \"wrong\" major version of Guile (e.g.,
+2.0 instead of 2.2), otherwise return PACKAGE."
+  (let ((guile (any (match-lambda
+                      ((label (? package? dep) _ ...)
+                       (and (string=? (package-name dep) "guile")
+                            dep)))
+                    (package-direct-inputs package))))
+    (and (or (not guile)
+             (string-prefix? guile-version
+                             (package-version guile)))
+         package)))
+
+(define (package-for-guile guile-version . names)
+  "Return the package with one of the given NAMES that depends on
+GUILE-VERSION (\"2.0\" or \"2.2\"), or #f if none of the packages matches."
+  (let loop ((names names))
+    (match names
+      (()
+       #f)
+      ((name rest ...)
+       (match (specification->package name)
+         (#f
+          (loop rest))
+         ((? package? package)
+          (or (false-if-wrong-guile package)
+              (loop rest))))))))
+
+(define specification->package
+  ;; Use our own variant of that procedure because that of (gnu packages)
+  ;; would traverse all the .scm files, which is wasteful.
+  (let ((ref (lambda (module variable)
+               (module-ref (resolve-interface module) variable))))
+    (match-lambda
+      ("guile"      (ref '(gnu packages commencement) 'guile-final))
+      ("guile-json" (ref '(gnu packages guile) 'guile-json))
+      ("guile-ssh"  (ref '(gnu packages ssh)   'guile-ssh))
+      ("guile-git"  (ref '(gnu packages guile) 'guile-git))
+      ("libgcrypt"  (ref '(gnu packages gnupg) 'libgcrypt))
+      ("zlib"       (ref '(gnu packages compression) 'zlib))
+      ("gzip"       (ref '(gnu packages compression) 'gzip))
+      ("bzip2"      (ref '(gnu packages compression) 'bzip2))
+      ("xz"         (ref '(gnu packages compression) 'xz))
+      ("guix"       (ref '(gnu packages package-management)
+                         'guix-register)))))
+
+
+;;;
+;;; Derivations.
+;;;
+
+;; Node in a DAG of build tasks.  Each node maps to a derivation, but it's
+;; easier to express things this way.
+(define-record-type <node>
+  (node name modules source dependencies compiled)
+  node?
+  (name          node-name)                       ;string
+  (modules       node-modules)                    ;list of module names
+  (source        node-source)                     ;list of source files
+  (dependencies  node-dependencies)               ;list of nodes
+  (compiled      node-compiled))                  ;node -> lowerable object
+
+(define (node-fold proc init nodes)
+  (let loop ((nodes nodes)
+             (visited (setq))
+             (result init))
+    (match nodes
+      (() result)
+      ((head tail ...)
+       (if (set-contains? visited head)
+           (loop tail visited result)
+           (loop tail (set-insert head visited)
+                 (proc head result)))))))
+
+(define (node-modules/recursive nodes)
+  (node-fold (lambda (node modules)
+               (append (node-modules node) modules))
+             '()
+             nodes))
+
+(define* (closure modules #:optional (except '()))
+  (source-module-closure modules
+                         #:select?
+                         (match-lambda
+                           (('guix 'config)
+                            #f)
+                           ((and module
+                                 (or ('guix _ ...) ('gnu _ ...)))
+                            (not (member module except)))
+                           (rest #f))))
+
+(define module->import
+  ;; Return a file-name/file-like object pair for the specified module and
+  ;; suitable for 'imported-files'.
+  (match-lambda
+    ((module '=> thing)
+     (let ((file (module-name->file-name module)))
+       (list file thing)))
+    (module
+        (let ((file (module-name->file-name module)))
+          (list file
+                (local-file (search-path %load-path file)))))))
+
+(define* (scheme-node name modules #:optional (dependencies '())
+                      #:key (extra-modules '()) (extra-files '())
+                      (extensions '())
+                      parallel? guile-for-build)
+  "Return a node that builds the given Scheme MODULES, and depends on
+DEPENDENCIES (a list of nodes).  EXTRA-MODULES is a list of additional modules
+added to the source, and EXTRA-FILES is a list of additional files.
+EXTENSIONS is a set of full-blown Guile packages (e.g., 'guile-json') that
+must be present in the search path."
+  (let* ((modules (append extra-modules
+                          (closure modules
+                                   (node-modules/recursive dependencies))))
+         (module-files (map module->import modules))
+         (source (imported-files (string-append name "-source")
+                                 (append module-files extra-files))))
+    (node name modules source dependencies
+          (compiled-modules name source modules
+                            (map node-source dependencies)
+                            (map node-compiled dependencies)
+                            #:extensions extensions
+                            #:parallel? parallel?
+                            #:guile-for-build guile-for-build))))
+
+(define (file-imports directory sub-directory pred)
+  "List all the files matching PRED under DIRECTORY/SUB-DIRECTORY.  Return a
+list of file-name/file-like objects suitable as inputs to 'imported-files'."
+  (map (lambda (file)
+         (list (string-drop file (+ 1 (string-length directory)))
+               (local-file file #:recursive? #t)))
+       (find-files (string-append directory "/" sub-directory) pred)))
+
+(define (scheme-modules* directory sub-directory)
+  "Return the list of module names found under SUB-DIRECTORY in DIRECTORY."
+  (let ((prefix (string-length directory)))
+    (map (lambda (file)
+           (file-name->module-name (string-drop file prefix)))
+         (scheme-files (string-append directory "/" sub-directory)))))
+
+(define* (compiled-guix source #:key (version %guix-version)
+                        (name (string-append "guix-" version))
+                        (guile-version (effective-version))
+                        (guile-for-build (guile-for-build guile-version))
+                        (libgcrypt (specification->package "libgcrypt"))
+                        (zlib (specification->package "zlib"))
+                        (gzip (specification->package "gzip"))
+                        (bzip2 (specification->package "bzip2"))
+                        (xz (specification->package "xz"))
+                        (guix (specification->package "guix")))
+  "Return a file-like object that contains a compiled Guix."
+  (define guile-json
+    (package-for-guile guile-version
+                       "guile-json"
+                       "guile2.2-json"
+                       "guile2.0-json"))
+
+  (define guile-ssh
+    (package-for-guile guile-version
+                       "guile-ssh"
+                       "guile2.2-ssh"
+                       "guile2.0-ssh"))
+
+  (define guile-git
+    (package-for-guile guile-version
+                       "guile-git"
+                       "guile2.0-git"))
+
+
+  (define dependencies
+    (match (append-map (lambda (package)
+                         (cons (list "x" package)
+                               (package-transitive-inputs package)))
+                       (list guile-git guile-json guile-ssh))
+      (((labels packages _ ...) ...)
+       packages)))
+
+  (define *core-modules*
+    (scheme-node "guix-core"
+                 '((guix)
+                   (guix monad-repl)
+                   (guix packages)
+                   (guix download)
+                   (guix discovery)
+                   (guix profiles)
+                   (guix build-system gnu)
+                   (guix build-system trivial)
+                   (guix build profiles)
+                   (guix build gnu-build-system))
+
+                 ;; Provide a dummy (guix config) with the default version
+                 ;; number, storedir, etc.  This is so that "guix-core" is the
+                 ;; same across all installations and doesn't need to be
+                 ;; rebuilt when the version changes, which in turn means we
+                 ;; can have substitutes for it.
+                 #:extra-modules
+                 `(((guix config)
+                    => ,(make-config.scm #:libgcrypt
+                                         (specification->package
+                                          "libgcrypt"))))
+
+                 #:guile-for-build guile-for-build))
+
+  (define *extra-modules*
+    (scheme-node "guix-extra"
+                 (filter-map (match-lambda
+                               (('guix 'scripts _ ..1) #f)
+                               (name name))
+                             (scheme-modules* source "guix"))
+                 (list *core-modules*)
+                 #:extensions dependencies
+                 #:guile-for-build guile-for-build))
+
+  (define *package-modules*
+    (scheme-node "guix-packages"
+                 `((gnu packages)
+                   ,@(scheme-modules* source "gnu/packages"))
+                 (list *core-modules* *extra-modules*)
+                 #:extensions dependencies
+                 #:extra-files                    ;all the non-Scheme files
+                 (file-imports source "gnu/packages"
+                               (lambda (file stat)
+                                 (and (eq? 'regular (stat:type stat))
+                                      (not (string-suffix? ".scm" file))
+                                      (not (string-suffix? ".go" file))
+                                      (not (string-prefix? ".#" file))
+                                      (not (string-suffix? "~" file)))))
+                 #:guile-for-build guile-for-build))
+
+  (define *system-modules*
+    (scheme-node "guix-system"
+                 `((gnu system)
+                   (gnu services)
+                   ,@(scheme-modules* source "gnu/system")
+                   ,@(scheme-modules* source "gnu/services"))
+                 (list *package-modules* *extra-modules* *core-modules*)
+                 #:extensions dependencies
+                 #:extra-files
+                 (file-imports source "gnu/system/examples" (const #t))
+                 #:guile-for-build
+                 guile-for-build))
+
+  (define *cli-modules*
+    (scheme-node "guix-cli"
+                 (scheme-modules* source "/guix/scripts")
+                 (list *core-modules* *extra-modules* *package-modules*
+                       *system-modules*)
+                 #:extensions dependencies
+                 #:guile-for-build guile-for-build))
+
+  (define *config*
+    (scheme-node "guix-config"
+                 '()
+                 #:extra-modules
+                 `(((guix config)
+                    => ,(make-config.scm #:libgcrypt libgcrypt
+                                         #:zlib zlib
+                                         #:gzip gzip
+                                         #:bzip2 bzip2
+                                         #:xz xz
+                                         #:guix guix
+                                         #:package-name
+                                         %guix-package-name
+                                         #:package-version
+                                         version
+                                         #:bug-report-address
+                                         %guix-bug-report-address
+                                         #:home-page-url
+                                         %guix-home-page-url)))
+                 #:guile-for-build guile-for-build))
+
+  (directory-union name
+                   (append-map (lambda (node)
+                                 (list (node-source node)
+                                       (node-compiled node)))
+
+                               ;; Note: *CONFIG* comes first so that it
+                               ;; overrides the (guix config) module that
+                               ;; comes with *CORE-MODULES*.
+                               (list *config*
+                                     *cli-modules*
+                                     *system-modules*
+                                     *package-modules*
+                                     *extra-modules*
+                                     *core-modules*))
+
+                   ;; Silently choose the first entry upon collision so that
+                   ;; we choose *CONFIG*.
+                   #:resolve-collision 'first
+
+                   ;; When we do (add-to-store "utils.scm"), "utils.scm" must
+                   ;; be a regular file, not a symlink.  Thus, arrange so that
+                   ;; regular files appear as regular files in the final
+                   ;; output.
+                   #:copy? #t
+                   #:quiet? #t))
+
+
+;;;
+;;; Generating (guix config).
+;;;
+
+(define %dependency-variables
+  ;; (guix config) variables corresponding to dependencies.
+  '(%libgcrypt %libz %xz %gzip %bzip2 %nix-instantiate
+    %sbindir %guix-register-program))
+
+(define %persona-variables
+  ;; (guix config) variables that define Guix's persona.
+  '(%guix-package-name
+    %guix-version
+    %guix-bug-report-address
+    %guix-home-page-url))
+
+(define %config-variables
+  ;; (guix config) variables corresponding to Guix configuration (storedir,
+  ;; localstatedir, etc.)
+  (sort (filter pair?
+                (module-map (lambda (name var)
+                              (and (not (memq name %dependency-variables))
+                                   (not (memq name %persona-variables))
+                                   (cons name (variable-ref var))))
+                            (resolve-interface '(guix config))))
+        (lambda (name+value1 name+value2)
+          (string<? (symbol->string (car name+value1))
+                    (symbol->string (car name+value2))))))
+
+(define* (make-config.scm #:key libgcrypt zlib gzip xz bzip2 guix
+                          (package-name "GNU Guix")
+                          (package-version "0")
+                          (bug-report-address "bug-guix@gnu.org")
+                          (home-page-url "https://gnu.org/s/guix"))
+
+  ;; Hack so that Geiser is not confused.
+  (define defmod 'define-module)
+
+  (scheme-file "config.scm"
+               #~(begin
+                   (#$defmod (guix config)
+                     #:export (%guix-package-name
+                               %guix-version
+                               %guix-bug-report-address
+                               %guix-home-page-url
+                               %sbindir
+                               %libgcrypt
+                               %libz
+                               %gzip
+                               %bzip2
+                               %xz
+                               %nix-instantiate))
+
+                   ;; XXX: Work around <http://bugs.gnu.org/15602>.
+                   (eval-when (expand load eval)
+                     #$@(map (match-lambda
+                               ((name . value)
+                                #~(define-public #$name #$value)))
+                             %config-variables)
+
+                     (define %guix-package-name #$package-name)
+                     (define %guix-version #$package-version)
+                     (define %guix-bug-report-address #$bug-report-address)
+                     (define %guix-home-page-url #$home-page-url)
+
+                     (define %sbindir
+                       ;; This is used to define '%guix-register-program'.
+                       ;; TODO: Use a derivation that builds nothing but the
+                       ;; C++ part.
+                       #+(and guix (file-append guix "/sbin")))
+
+                     (define %guix-register-program
+                       (or (getenv "GUIX_REGISTER")
+                           (and %sbindir
+                                (string-append %sbindir "/guix-register"))))
+
+                     (define %gzip
+                       #+(and gzip (file-append gzip "/bin/gzip")))
+                     (define %bzip2
+                       #+(and bzip2 (file-append bzip2 "/bin/bzip2")))
+                     (define %xz
+                       #+(and xz (file-append xz "/bin/xz")))
+
+                     (define %libgcrypt
+                       #+(and libgcrypt
+                              (file-append libgcrypt "/lib/libgcrypt")))
+                     (define %libz
+                       #+(and zlib
+                              (file-append zlib "/lib/libz")))
+
+                     (define %nix-instantiate     ;for (guix import snix)
+                       "nix-instantiate")))))
+
+
+
+;;;
+;;; Building.
+;;;
+
+(define (imported-files name files)
+  ;; This is a non-monadic, simplified version of 'imported-files' from (guix
+  ;; gexp).
+  (define build
+    (with-imported-modules (source-module-closure
+                            '((guix build utils)))
+      #~(begin
+          (use-modules (ice-9 match)
+                       (guix build utils))
+
+          (mkdir (ungexp output)) (chdir (ungexp output))
+          (for-each (match-lambda
+                      ((final-path store-path)
+                       (mkdir-p (dirname final-path))
+
+                       ;; Note: We need regular files to be regular files, not
+                       ;; symlinks, as this makes a difference for
+                       ;; 'add-to-store'.
+                       (copy-file store-path final-path)))
+                    '#$files))))
+
+  (computed-file name build))
+
+(define* (compiled-modules name module-tree modules
+                           #:optional
+                           (dependencies '())
+                           (dependencies-compiled '())
+                           #:key
+                           (extensions '())       ;full-blown Guile packages
+                           parallel?
+                           guile-for-build)
+  ;; This is a non-monadic, enhanced version of 'compiled-file' from (guix
+  ;; gexp).
+  (define build
+    (with-imported-modules (source-module-closure
+                            '((guix build compile)
+                              (guix build utils)))
+      #~(begin
+          (use-modules (srfi srfi-26)
+                       (ice-9 match)
+                       (ice-9 format)
+                       (ice-9 threads)
+                       (guix build compile)
+                       (guix build utils))
+
+          (define (regular? file)
+            (not (member file '("." ".."))))
+
+          (define (report-load file total completed)
+            (display #\cr)
+            (format #t
+                    "loading...\t~5,1f% of ~d files" ;FIXME: i18n
+                    (* 100. (/ completed total)) total)
+            (force-output))
+
+          (define (report-compilation file total completed)
+            (display #\cr)
+            (format #t "compiling...\t~5,1f% of ~d files" ;FIXME: i18n
+                    (* 100. (/ completed total)) total)
+            (force-output))
+
+          (define (process-directory directory output)
+            (let ((files  (find-files directory "\\.scm$"))
+                  (prefix (+ 1 (string-length directory))))
+              ;; Hide compilation warnings.
+              (parameterize ((current-warning-port (%make-void-port "w")))
+                (compile-files directory #$output
+                               (map (cut string-drop <> prefix) files)
+                               #:workers (parallel-job-count)
+                               #:report-load report-load
+                               #:report-compilation report-compilation))))
+
+          (setvbuf (current-output-port) _IONBF)
+          (setvbuf (current-error-port) _IONBF)
+
+          (set! %load-path (cons #+module-tree %load-path))
+          (set! %load-path
+            (append '#+dependencies
+                    (map (lambda (extension)
+                           (string-append extension "/share/guile/site/"
+                                          (effective-version)))
+                         '#+extensions)
+                    %load-path))
+
+          (set! %load-compiled-path
+            (append '#+dependencies-compiled
+                    (map (lambda (extension)
+                           (string-append extension "/lib/guile/"
+                                          (effective-version)
+                                          "/site-ccache"))
+                         '#+extensions)
+                    %load-compiled-path))
+
+          ;; Load the compiler modules upfront.
+          (compile #f)
+
+          (mkdir #$output)
+          (chdir #+module-tree)
+          (process-directory "." #$output))))
+
+  (computed-file name build
+                 #:guile guile-for-build
+                 #:options
+                 `(#:local-build? #f              ;allow substitutes
+
+                   ;; Don't annoy people about _IONBF deprecation.
+                   #:env-vars (("GUILE_WARN_DEPRECATED" . "no")))))
+
+
+;;;
+;;; Building.
+;;;
+
+(define (guile-for-build version)
+  "Return a derivation for Guile 2.0 or 2.2, whichever matches the currently
+running Guile."
+  (define canonical-package                       ;soft reference
+    (module-ref (resolve-interface '(gnu packages base))
+                'canonical-package))
+
+  (match version
+    ("2.2.2"
+     ;; Gross hack to avoid ABI incompatibilities (see
+     ;; <https://bugs.gnu.org/29570>.)
+     (module-ref (resolve-interface '(gnu packages guile))
+                 'guile-2.2.2))
+    ("2.2"
+     (canonical-package (module-ref (resolve-interface '(gnu packages guile))
+                                    'guile-2.2/fixed)))
+    ("2.0"
+     (canonical-package (specification->package "guile@2.0")))))
+
+(define* (guix-derivation source version
+                          #:optional (guile-version (effective-version)))
+  "Return, as a monadic value, the derivation to build the Guix from SOURCE
+for GUILE-VERSION.  Use VERSION as the version string."
+  (define (shorten version)
+    (if (and (string-every char-set:hex-digit version)
+             (> (string-length version) 9))
+        (string-take version 9)                   ;Git commit
+        version))
+
+  (define guile
+    (guile-for-build guile-version))
+
+  (mbegin %store-monad
+    (set-guile-for-build guile)
+    (lower-object (compiled-guix source
+                                 #:version version
+                                 #:name (string-append "guix-"
+                                                       (shorten version))
+                                 #:guile-version (match guile-version
+                                                   ("2.2.2" "2.2")
+                                                   (version version))
+                                 #:guile-for-build guile))))
diff --git a/guix/upstream.scm b/guix/upstream.scm
index caaa0e44e4..9e1056f7a7 100644
--- a/guix/upstream.scm
+++ b/guix/upstream.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015 Alex Kost <alezost@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -153,7 +153,8 @@ correspond to the same version."
   (cons (resolve-interface '(guix gnu-maintenance))
         (all-modules (map (lambda (entry)
                             `(,entry . "guix/import"))
-                          %load-path))))
+                          %load-path)
+                     #:warn warn-about-load-error)))
 
 (define %updaters
   ;; The list of publically-known updaters.