On Jan 29, Robby Findler wrote:
> You are suggesting that planet and drscheme collaborate directly via
> some parameter that planet exports that tells it to parse the line
> but return a dummy info if the package is not installed? (and use
> various security measures to forbid network access in addition)
>
> I think that makes sense.
No, I'm saying that if you forbid network access (via a security
guard), then you don't even need to extend planet. It was a little
tricky since the first thing I tried got caught by planet (see big
comment), but the following should be a fine version. It seems to me
like this works even better than a planet hook, since it will work
with any kind of network hook in the resolver (for example, some
future (require (url ...)) thing or whatever).
Any ideas about a good place to dump lang-related functions like this?
(More will be necessary, since the currentl available functionality is
pretty low level, and should be wrapped for more convenient user
consumption.)
#lang scheme/base
(define (call-without-network thunk on-network-attempt)
;; Could be done by throwing some specific exception and testing for its
type
;; in the with-handlers, but planet will catch network errors and re-raise
;; its own errors. (If it catches only `exn:fail:network?' then this could
;; be done with a separate kind of exception, but what if planet changes to
;; catch all errors?)
(define orig-security (current-security-guard))
(define connection-attempted #f)
(with-handlers ([exn? (lambda (e)
(if connection-attempted
(on-network-attempt)
(raise e)))])
(parameterize ([current-security-guard
(make-security-guard
orig-security
(lambda (what path modes) #t)
(lambda (what host port mode)
(set! connection-attempted #t)
(error 'poof "poof")))])
(thunk))))
(define (lang-text str #:allow-network [net-ok? #f])
(define (get-it)
(let* ([i (open-input-string str)]
[l (read-language i (lambda () #f))]
[l (and l (substring str 0 (file-position i)))]
[l (and l (regexp-match #px"^\\s*#(?:!|lang ) *(.*\\S)\\s*$" l))]
[l (and l (cadr l))])
l))
(if net-ok? (get-it) (call-without-network get-it (lambda () #f))))
(lang-text "#lang at-exp scheme/base")
(lang-text "#lang reader (lib \"scribble/reader.ss\")")
(lang-text "#lang reader (planet planet/test-connection/test-connection)")
(lang-text "#lang reader (planet planet/test-connection/test-connection)"
#:allow-network #t)
(lang-text "#lang reader (planet planet/test-connection/test-connection)")
--
((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://barzilay.org/ Maze is Life!
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