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#lang racket/base
(require racket/match
"stack-checkpoint.rkt"
"util.rkt")
(provide get-interaction)
;; Note: We handle eof-object? and exn:fail:network? by doing an exit
;; and letting the exit-handler in run.rkt cleanup the TCP connection.
;; This handles the case where e.g. the user kills the REPL buffer and
;; its process on the client/Emacs side. We used to have code here in
;; an effort support lang/datalog using eof as an expression separator
;; -- but that just causes an endless loop 100% CPU spike with an
;; abandoned tcp-input-port. So give up on that, reverting issue #305.
(define (get-interaction prompt)
;; Using with-handlers here would be a mistake; see #543.
(call-with-exception-handler
(λ (e)
(cond [(exn:fail:network? e)
(log-racket-mode-info "get-interaction: exn:fail:network")
(exit 'get-interaction-exn:fail:network)]
[else e]))
(λ ()
(define in ((current-get-interaction-input-port)))
(unless (already-more-to-read? in) ;#311
(display-prompt prompt))
(match (with-stack-checkpoint
((current-read-interaction) prompt in))
[(? eof-object?)
(log-racket-mode-info "get-interaction: eof")
(exit 'get-interaction-eof)]
[v
(zero-column!)
v]))))
(define (already-more-to-read? in)
;; Is there already at least one more read-able expression on in?
;;
;; - Use a "peeking read" so that, if the answer is yes, we don't
;; actually consume it (which could cause #449).
;;
;; - Use a thread + channel + sync/timeout so that, if the answer is
;; no because there is only a partial sexp -- e.g. "(+ 1" -- we
;; don't get stuck here.
(define ch (make-channel))
(thread
(λ ()
(channel-put ch
(with-handlers ([exn:fail? (λ _ #f)])
(let* ([buf (make-bytes 4096 0)]
[len (peek-bytes-avail!* buf 0 #f in)]
[bstr (subbytes buf 0 len)]
[v (read (open-input-bytes bstr))])
(not (eof-object? v)))))))
(sync/timeout 0.01 ch))
(define (display-prompt str)
(fresh-line)
(display str)
(display "> ")
(flush-output))
|
