Hello everyone,
I am working on this project: https://gitlab.com/HiPhish/MsgPack.rkt/
I am writing test cases and I ran into a problem with my ‘ext’ structure. It is
declared in the file ‘msgpack/main.rkt’, which is required in the file
‘msgpack/pack.rkt’ (also in ‘msgpack/unpack.rkt’). For my test case the test
file looks like this:
(require
quickcheck
rackunit/quickcheck
(file "../../msgpack/main.rkt")
(file "../../msgpack/pack.rkt"))
(check-property
(property ()
(let ([obj (ext #x01 (bytes #x02))])
(bytes=? (call-with-output-bytes (λ (out) (pack obj out)))
(bytes-append (bytes #xD4 (ext-type obj))
(ext-data obj))))))
Here is what happens from my understanding: when I required ‘main.rkt’ the
structure declaration got evaluated, creating all the functions that go along
with it, including ‘ext’ and ‘ext?’. Then when I required the ‘pack.rkt’ file
those declarations got evaluated again and created a new set of ext-related
functions that just happen to have the same name. This is why I the object I’m
trying to pack falls through all the ‘cont’ cases.
This isn’t limited to the test file, I also tried the following on the REPL
with the same results:
Welcome to Racket v6.9.
> (require msgpack msgpack/pack)
> (define e (ext 1 (bytes 2 3)))
> (define out (open-output-bytes))
> (pack e out)
; Type not supported by MessagePack [,bt for context]
> (pack-ext e out)
; pack-ext: contract violation
; expected: ext?
; given: #<ext>
; in: the 1st argument of
; (->
; ext?
; (and/c output-port? (not/c port-closed?))
; any)
; contract from:
; <pkgs>/msgpack-rkt/msgpack/pack.rkt
; blaming: top-level
; (assuming the contract is correct)
; at: <pkgs>/msgpack-rkt/msgpack/pack.rkt:53.5
; [,bt for context]
> ,bt
; pack-ext: contract violation
; expected: ext?
; given: #<ext>
; in: the 1st argument of
; (->
; ext?
; (and/c output-port? (not/c port-closed?))
; any)
; contract from:
; <pkgs>/msgpack-rkt/msgpack/pack.rkt
; blaming: top-level
; (assuming the contract is correct)
; at: <pkgs>/msgpack-rkt/msgpack/pack.rkt:53.5
; context...:
;
/usr/local/Cellar/minimal-racket/6.9/share/racket/collects/racket/contract/private/blame.rkt:159:0:
raise-blame-error16
;
/usr/local/Cellar/minimal-racket/6.9/share/racket/collects/racket/contract/private/arrow-val-first.rkt:357:18
;
/usr/local/Cellar/minimal-racket/6.9/share/racket/pkgs/xrepl-lib/xrepl/xrepl.rkt:1448:0
;
/usr/local/Cellar/minimal-racket/6.9/share/racket/collects/racket/private/misc.rkt:88:7
>
Adding a ‘#:prefab’ to the end of the struct declaration does not solve the
problem. What am I doing wrong? Both the packing and unpacking need the ‘ext’
type for conformance with MessagePack. Do I have to make a large umbrella
module that provides the entire API? I would prefer is users could just
‘require’ parts of the library as they need them (i.e. only ‘(require
msgpack/pack)’ if you only want to unpack data).
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