Add (guix inferior) and (guix scripts repl).

* guix/inferior.scm, guix/scripts/repl.scm, tests/inferior.scm: New
files.
* Makefile.am (MODULES): Add 'guix/scripts/repl.scm' and
'guix/inferior.scm'.
(SCM_TESTS): Add 'tests/inferior.scm'.
* doc/guix.texi (Invoking guix repl): New node.

1 files changed, 197 insertions, 0 deletions

diff --git a/guix/inferior.scm b/guix/inferior.scm
new file mode 100644
index 0000000000..629c2c4313
--- /dev/null
+++ b/guix/inferior.scm
@@ -0,0 +1,197 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 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 inferior)
+  #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-9 gnu)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 popen)
+  #:export (inferior?
+            open-inferior
+            close-inferior
+            inferior-eval
+            inferior-object?
+
+            inferior-package?
+            inferior-package-name
+            inferior-package-version
+
+            inferior-packages
+            inferior-package-synopsis
+            inferior-package-description))
+
+;;; Commentary:
+;;;
+;;; This module provides a way to spawn Guix "inferior" processes and to talk
+;;; to them.  It allows us, from one instance of Guix, to interact with
+;;; another instance of Guix coming from a different commit.
+;;;
+;;; Code:
+
+;; Inferior Guix process.
+(define-record-type <inferior>
+  (inferior pid socket version)
+  inferior?
+  (pid      inferior-pid)
+  (socket   inferior-socket)
+  (version  inferior-version))                    ;REPL protocol version
+
+(define (inferior-pipe directory command)
+  "Return an input/output pipe on the Guix instance in DIRECTORY.  This runs
+'DIRECTORY/COMMAND repl' if it exists, or falls back to some other method if
+it's an old Guix."
+  (let ((pipe (with-error-to-port (%make-void-port "w")
+                (lambda ()
+                  (open-pipe* OPEN_BOTH
+                              (string-append directory "/" command)
+                              "repl" "-t" "machine")))))
+    (if (eof-object? (peek-char pipe))
+        (begin
+          (close-pipe pipe)
+
+          ;; Older versions of Guix didn't have a 'guix repl' command, so
+          ;; emulate it.
+          (open-pipe* OPEN_BOTH "guile"
+                      "-L" (string-append directory "/share/guile/site/"
+                                          (effective-version))
+                      "-C" (string-append directory "/share/guile/site/"
+                                          (effective-version))
+                      "-C" (string-append directory "/lib/guile/"
+                                          (effective-version) "/site-ccache")
+                      "-c"
+                      (object->string
+                       `(begin
+                          (primitive-load ,(search-path %load-path
+                                                        "guix/scripts/repl.scm"))
+                          ((@ (guix scripts repl) machine-repl))))))
+        pipe)))
+
+(define* (open-inferior directory #:key (command "bin/guix"))
+  "Open the inferior Guix in DIRECTORY, running 'DIRECTORY/COMMAND repl' or
+equivalent.  Return #f if the inferior could not be launched."
+  (define pipe
+    (inferior-pipe directory command))
+
+  (setvbuf pipe _IOLBF)
+  (match (read pipe)
+    (('repl-version 0 rest ...)
+     (let ((result (inferior 'pipe pipe (cons 0 rest))))
+       (inferior-eval '(use-modules (guix)) result)
+       (inferior-eval '(use-modules (gnu)) result)
+       (inferior-eval '(define %package-table (make-hash-table))
+                      result)
+       result))
+    (_
+     #f)))
+
+(define (close-inferior inferior)
+  "Close INFERIOR."
+  (close-pipe (inferior-socket inferior)))
+
+;; Non-self-quoting object of the inferior.
+(define-record-type <inferior-object>
+  (inferior-object address appearance)
+  inferior-object?
+  (address     inferior-object-address)
+  (appearance  inferior-object-appearance))
+
+(define (write-inferior-object object port)
+  (match object
+    (($ <inferior-object> _ appearance)
+     (format port "#<inferior-object ~a>" appearance))))
+
+(set-record-type-printer! <inferior-object> write-inferior-object)
+
+(define (inferior-eval exp inferior)
+  "Evaluate EXP in INFERIOR."
+  (define sexp->object
+    (match-lambda
+      (('value value)
+       value)
+      (('non-self-quoting address string)
+       (inferior-object address string))))
+
+  (write exp (inferior-socket inferior))
+  (newline (inferior-socket inferior))
+  (match (read (inferior-socket inferior))
+    (('values objects ...)
+     (apply values (map sexp->object objects)))
+    (('exception key objects ...)
+     (apply throw key (map sexp->object objects)))))
+
+
+;;;
+;;; Inferior packages.
+;;;
+
+(define-record-type <inferior-package>
+  (inferior-package inferior name version id)
+  inferior-package?
+  (inferior   inferior-package-inferior)
+  (name       inferior-package-name)
+  (version    inferior-package-version)
+  (id         inferior-package-id))
+
+(define (write-inferior-package package port)
+  (match package
+    (($ <inferior-package> _ name version)
+     (format port "#<inferior-package ~a@~a ~a>"
+             name version
+             (number->string (object-address package) 16)))))
+
+(set-record-type-printer! <inferior-package> write-inferior-package)
+
+(define (inferior-packages inferior)
+  "Return the list of packages known to INFERIOR."
+  (let ((result (inferior-eval
+                 '(fold-packages (lambda (package result)
+                                   (let ((id (object-address package)))
+                                     (hashv-set! %package-table id package)
+                                     (cons (list (package-name package)
+                                                 (package-version package)
+                                                 id)
+                                           result)))
+                                 '())
+                 inferior)))
+    (map (match-lambda
+           ((name version id)
+            (inferior-package inferior name version id)))
+         result)))
+
+(define (inferior-package-field package getter)
+  "Return the field of PACKAGE, an inferior package, accessed with GETTER."
+  (let ((inferior (inferior-package-inferior package))
+        (id       (inferior-package-id package)))
+    (inferior-eval `(,getter (hashv-ref %package-table ,id))
+                   inferior)))
+
+(define* (inferior-package-synopsis package #:key (translate? #t))
+  "Return the Texinfo synopsis of PACKAGE, an inferior package.  When
+TRANSLATE? is true, translate it to the current locale's language."
+  (inferior-package-field package
+                          (if translate?
+                              '(compose (@ (guix ui) P_) package-synopsis)
+                              'package-synopsis)))
+
+(define* (inferior-package-description package #:key (translate? #t))
+  "Return the Texinfo description of PACKAGE, an inferior package.  When
+TRANSLATE? is true, translate it to the current locale's language."
+  (inferior-package-field package
+                          (if translate?
+                              '(compose (@ (guix ui) P_) package-description)
+                              'package-description)))