72 lines
2.7 KiB

#lang racket/base
(require "../src/data.rkt"
(module+ test
(require rackunit))
(define (thread-values . thunks)
(parameterize-break #t
(define the-exn (box #f))
(define original-thread (current-thread))
(define (break e)
(when (box-cas! the-exn #f e)
(break-thread original-thread))
(sleep 0))
(define-values (threads channels)
(for/fold ([ts null]
[chs null]
#:result (values (reverse ts) (reverse chs)))
([th thunks])
(define ch (make-channel))
(define t
(thread (λ ()
(with-handlers ([exn? break])
(channel-put ch (th))))))
(values (cons t ts) (cons ch chs))))
(with-handlers ([exn:break? (λ (_)
(for ([t threads]) (kill-thread t))
(if (unbox the-exn)
(raise (unbox the-exn))
(error 'thread-values "a thread broke, but without reporting its exception")))])
(for/list ([ch channels])
(channel-get ch))))))
(module+ test
; check that they actually execute concurrently
(define ch (make-channel))
(check-equal? (let-values ([(a b)
(λ ()
(channel-put ch 'a)
(channel-get ch)))
(λ ()
(channel-get ch)
(channel-put ch 'b))))])
(list a b))
'(b a))
; check that it assigns the correct value to the correct variable
(check-equal? (let-values ([(a b)
(λ () (sleep 0) 'a)
(λ () 'b))])
(list a b))
'(a b))
; check that exceptions are passed to the original thread, and other threads are killed
;; TODO: if the other thread was making an HTTP request, could it be left stuck open by the kill?
(check-equal? (let* ([x "!"]
(with-handlers ([exn:fail:user? (λ (e) (exn-message e))])
(λ () (sleep 0) (set! x "?") (println "this side effect should not happen"))
(λ () (raise-user-error "catch me"))))])
(string-append res x))
"catch me!"))