2b0a370d00
* guix/repl.scm (repl-prompt): New variable. (stack->frames): New procedure. (send-repl-response)[frame->sexp, handle-exception]: New procedure. Pass HANDLE-EXCEPTION as a pre-unwind handler. (machine-repl): Define 'tag'. Bump protocol version to (0 1 1). Wrap 'loop' call in 'call-with-prompt'.
143 lines
4.8 KiB
Scheme
143 lines
4.8 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (guix repl)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-26)
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#:use-module (ice-9 match)
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#:export (send-repl-response
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machine-repl))
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;;; Commentary:
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;;;
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;;; This module implements the "machine-readable" REPL provided by
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;;; 'guix repl -t machine'. It's a lightweight module meant to be
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;;; embedded in any Guile process providing REPL functionality.
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;;;
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;;; Code:
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(define (self-quoting? x)
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"Return #t if X is self-quoting."
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(letrec-syntax ((one-of (syntax-rules ()
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((_) #f)
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((_ pred rest ...)
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(or (pred x)
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(one-of rest ...))))))
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(one-of symbol? string? keyword? pair? null? array?
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number? boolean? char?)))
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(define repl-prompt
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;; Current REPL prompt or #f.
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(make-parameter #f))
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(define (stack->frames stack)
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"Return STACK's frames as a list."
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(unfold (cute >= <> (stack-length stack))
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(cut stack-ref stack <>)
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1+
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0))
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(define* (send-repl-response exp output
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#:key (version '(0 0)))
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"Write the response corresponding to the evaluation of EXP to PORT, an
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output port. VERSION is the client's protocol version we are targeting."
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(define (value->sexp value)
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(if (self-quoting? value)
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`(value ,value)
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`(non-self-quoting ,(object-address value)
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,(object->string value))))
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(define (frame->sexp frame)
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`(,(frame-procedure-name frame)
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,(match (frame-source frame)
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((_ (? string? file) (? integer? line) . (? integer? column))
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(list file line column))
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(_
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'(#f #f #f)))))
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(define (handle-exception key . args)
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(define reply
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(match version
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((0 1 (? positive?) _ ...)
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;; Protocol (0 1 1) and later.
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(let ((stack (if (repl-prompt)
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(make-stack #t handle-exception (repl-prompt))
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(make-stack #t))))
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`(exception (arguments ,key ,@(map value->sexp args))
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(stack ,@(map frame->sexp (stack->frames stack))))))
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(_
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;; Protocol (0 0).
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`(exception ,key ,@(map value->sexp args)))))
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(write reply output)
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(newline output)
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(force-output output))
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(catch #t
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(lambda ()
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(let ((results (call-with-values
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(lambda ()
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(primitive-eval exp))
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list)))
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(write `(values ,@(map value->sexp results))
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output)
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(newline output)
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(force-output output)))
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(const #t)
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handle-exception))
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(define* (machine-repl #:optional
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(input (current-input-port))
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(output (current-output-port)))
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"Run a machine-usable REPL over ports INPUT and OUTPUT.
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The protocol of this REPL is meant to be machine-readable and provides proper
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support to represent multiple-value returns, exceptions, objects that lack a
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read syntax, and so on. As such it is more convenient and robust than parsing
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Guile's REPL prompt."
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(define tag
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(make-prompt-tag "repl-prompt"))
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(define (loop exp version)
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(match exp
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((? eof-object?) #t)
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(exp
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(send-repl-response exp output
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#:version version)
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(loop (read input) version))))
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(write `(repl-version 0 1 1) output)
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(newline output)
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(force-output output)
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;; In protocol version (0 0), clients would not send their supported
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;; protocol version. Thus, the code below checks for two case: (1) a (0 0)
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;; client that directly sends an expression to evaluate, and (2) a more
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;; recent client that sends (() repl-version ...). This form is chosen to
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;; be unambiguously distinguishable from a regular Scheme expression.
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(call-with-prompt tag
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(lambda ()
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(parameterize ((repl-prompt tag))
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(match (read input)
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((() 'repl-version version ...)
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(loop (read input) version))
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(exp
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(loop exp '(0 0))))))
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(const #f)))
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