[racket] module+ test... (require rackunit) results in unbound identifier when used in macro

From: Carl Eastlund (carl.eastlund at gmail.com)
Date: Wed Jan 8 17:37:26 EST 2014

I do not suggest rebinding the whole body like that; it could be seriously
problematic if the user refers to something not viable to the macro
definition.  What you need to rebind is the name "rackunit" itself passed
to require so that it has the context of the macro application.  That way
the names bound by the require will be visible to the macro user.
On Jan 8, 2014 5:29 PM, "Stephen Chang" <stchang at ccs.neu.edu> wrote:

> The problem is that check-true (and check-false) are not in scope (as
> you discovered) during expansion. Here is one way to fix your problem
> by recapturing the test expressions to have the proper context. You
> can also use syntax-local-introduce instead of the lambda (someone
> correct me if this is not proper usage).
>
> #lang racket
> (require (for-syntax syntax/parse))
>
> (define-syntax (define/test stx)
>   (syntax-parse stx
>     [(_ (id arg ...) body ... #:test test-body ...)
>      (with-syntax ([id-str (symbol->string (syntax->datum #'id))]
>                    [(new-test-body ...)
>                     (map
>                      (λ (s) (datum->syntax #'here (syntax->datum s)))
>                      (syntax->list #'(test-body ...)))])
>        #'(begin
>            (define (id arg ...) body ...)
>            (print id-str)
>            (module+ test
>              (require rackunit)
>              (test-case id-str
>                         new-test-body ...))))]))
>
> (define/test (my-fn a b c)
>   (print a)
>   (print b)
>   (print c)
>   #:test
>   (check-true #t)
>   (check-false #t))
>
> On Wed, Jan 8, 2014 at 4:53 PM, Scott Klarenbach <scott at pointyhat.ca>
> wrote:
> > I have the following macro:
> >
> > (define-syntax (define/test stx)
> >   (syntax-parse stx
> > [(_ (id arg ...) body ... #:test test-body ...)
> > (with-syntax ([id-str (symbol->string (syntax->datum #'id))])
> >   #'(begin
> >   (define (id arg ...) body ...)
> >   (print id-str)
> >   (module+ test
> > (require rackunit)
> > (test-case id-str
> >   test-body ...))))]))
> >
> > Which handles some testing boilerplate and allows me to use it like so:
> >
> > (define/test (my-fn a b c)
> >   (print a)
> >   (print b)
> >   (print c)
> >   #:test
> >   (check-true #t)
> >   (check-false #t))
> >
> > The problem is that the (require rackunit) expression inside of (module+
> > test) is not being picked up after macro expansion.  Running either the
> code
> > or the tests (via raco test) results in: unbound identifier check-true.
> >
> > Adding (module+ (require rackunit)) to the top of the file solves the
> > problem and both the file and tests run as expected.
> >
> > What am I missing?
> >
> > Thanks.
> > --
> > Talk to you soon,
> >
> > Scott Klarenbach
> >
> > PointyHat Software Corp.
> > www.pointyhat.ca
> > p 604-568-4280
> > e scott at pointyhat.ca
> > 200-1575 W. Georgia
> > Vancouver, BC V6G2V3
> >
> > _______________________________________
> > To iterate is human; to recur, divine
> >
> > ____________________
> >   Racket Users list:
> >   http://lists.racket-lang.org/users
> >
>
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