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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018, 2019, 2020 Ludovic Courtès <>
;;; 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
;;; 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 <>.
(define-module (guix repl)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-26)
#:use-module (ice-9 match)
#:export (send-repl-response
;;; 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? keyword? pair? null? array?
number? boolean? char?)))
(define repl-prompt
;; Current REPL prompt or #f.
(make-parameter #f))
(define (stack->frames stack)
"Return STACK's frames as a list."
(unfold (cute >= <> (stack-length stack))
(cut stack-ref stack <>)
(define* (send-repl-response exp output
#:key (version '(0 0)))
"Write the response corresponding to the evaluation of EXP to PORT, an
output port. VERSION is the client's protocol version we are targeting."
(define (value->sexp value)
(if (self-quoting? value)
`(value ,value)
`(non-self-quoting ,(object-address value)
,(object->string value))))
(define (frame->sexp frame)
`(,(frame-procedure-name frame)
,(match (frame-source frame)
((_ (? string? file) (? integer? line) . (? integer? column))
(list file line column))
'(#f #f #f)))))
(define (handle-exception key . args)
(define reply
(match version
((0 1 (? positive?) _ ...)
;; Protocol (0 1 1) and later.
(let ((stack (if (repl-prompt)
(make-stack #t handle-exception (repl-prompt))
(make-stack #t))))
`(exception (arguments ,key ,@(map value->sexp args))
(stack ,@(map frame->sexp (stack->frames stack))))))
;; Protocol (0 0).
`(exception ,key ,@(map value->sexp args)))))
(write reply output)
(newline output)
(force-output output))
(catch #t
(lambda ()
(let ((results (call-with-values
(lambda ()
(primitive-eval exp))
(write `(values ,@(map value->sexp results))
(newline output)
(force-output output)))
(const #t)
(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."
(define tag
(make-prompt-tag "repl-prompt"))
(define (loop exp version)
(match exp
((? eof-object?) #t)
(send-repl-response exp output
#:version version)
(loop (read input) version))))
(write `(repl-version 0 1 1) output)
(newline output)
(force-output output)
;; In protocol version (0 0), clients would not send their supported
;; protocol version. Thus, the code below checks for two case: (1) a (0 0)
;; client that directly sends an expression to evaluate, and (2) a more
;; recent client that sends (() repl-version ...). This form is chosen to
;; be unambiguously distinguishable from a regular Scheme expression.
(call-with-prompt tag
(lambda ()
(parameterize ((repl-prompt tag))
(match (read input)
((() 'repl-version version ...)
(loop (read input) version))
(loop exp '(0 0))))))
(const #f)))