Add (guix repl).

* guix/scripts/repl.scm: Use (guix repl).
(self-quoting?, machine-repl): Remove.
* guix/repl.scm: New file.
* Makefile.am (MODULES): Add it.

1 files changed, 86 insertions, 0 deletions

diff --git a/guix/repl.scm b/guix/repl.scm
new file mode 100644
index 0000000000..5cff5c71e9
--- /dev/null
+++ b/guix/repl.scm
@@ -0,0 +1,86 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2018, 2019 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 repl)
+  #:use-module (rnrs bytevectors)
+  #:use-module (ice-9 match)
+  #:export (send-repl-response
+            machine-repl))
+
+;;; Commentary:
+;;;
+;;; This module implements the "machine-readable" REPL provided by
+;;; 'guix repl -t machine'.  It's a lightweight module meant to be
+;;; embedded in any Guile process providing REPL functionality.
+;;;
+;;; Code:
+
+(define (self-quoting? x)
+  "Return #t if X is self-quoting."
+  (letrec-syntax ((one-of (syntax-rules ()
+                            ((_) #f)
+                            ((_ pred rest ...)
+                             (or (pred x)
+                                 (one-of rest ...))))))
+    (one-of symbol? string? pair? null? vector?
+            bytevector? number? boolean?)))
+
+
+(define (send-repl-response exp output)
+  "Write the response corresponding to the evaluation of EXP to PORT, an
+output port."
+  (define (value->sexp value)
+    (if (self-quoting? value)
+        `(value ,value)
+        `(non-self-quoting ,(object-address value)
+                           ,(object->string value))))
+
+  (catch #t
+    (lambda ()
+      (let ((results (call-with-values
+                         (lambda ()
+                           (primitive-eval exp))
+                       list)))
+        (write `(values ,@(map value->sexp results))
+               output)
+        (newline output)
+        (force-output output)))
+    (lambda (key . args)
+      (write `(exception ,key ,@(map value->sexp args)))
+      (newline output)
+      (force-output output))))
+
+(define* (machine-repl #:optional
+                       (input (current-input-port))
+                       (output (current-output-port)))
+  "Run a machine-usable REPL over ports INPUT and OUTPUT.
+
+The protocol of this REPL is meant to be machine-readable and provides proper
+support to represent multiple-value returns, exceptions, objects that lack a
+read syntax, and so on.  As such it is more convenient and robust than parsing
+Guile's REPL prompt."
+  (write `(repl-version 0 0) output)
+  (newline output)
+  (force-output output)
+
+  (let loop ()
+    (match (read input)
+      ((? eof-object?) #t)
+      (exp
+       (send-repl-response exp output)
+       (loop)))))