Error in ZnZincServerAdaptor when extracting the body in a multipart/mixed request

[eMaringolo]

When Seaside tries to extract the body from a multipart/mixed request it causes an error since the rule used in ZnZincServerAdaptor>>requestBodyFor: aZincRequest to determine the body assumes the request entity might be a bytearray instead of a ZnMultiPartFormDataEntity

requestBodyFor: aZincRequest
  ^ (aZincRequest method ~= #TRACE 
    and: [ aZincRequest hasEntity
      and: [ aZincRequest entity isEmpty not
        and: [ (aZincRequest entity contentType matches: ZnMimeType applicationFormUrlEncoded) not
          and: [ (aZincRequest entity contentType matches: ZnMimeType multiPartFormData) not ] ] ] ])
            ifTrue: [
              "Seaside wants to do its own text conversions"
	      aZincRequest entity bytes asString ] "<-- ZnMultiPartFormDataEntity does not understand #bytes"
	    ifFalse: [ String new ]

How to reproduce

Create a REST Restful handler at /rest with the following route

multipartMixed
	<post>
	<path: '/multipart1'>

Run the following request against the handler:

curl -X POST -H 'Content-type:multipart/mixed' \
   -F "text=Plain content;type=text/plain" \
   -F 'json={"foo": [1, true], "baz": "bar"};type=application/json'  \
   http://localhost:8080/rest/multipart1

[eMaringolo]

It is not clear to me whether there is a bug in the handling, or the request is malformed.

[theseion]

I that piece of code needs to be improved. I've stumbled over the same thing when implementing streaming requests. The conditional is just not flexible enough to handle all possible cases.

[eMaringolo]

The "proper" solution I see is to reify the body as an entity, which for most cases will be a simple one (as it is now) or a composite/multipart one (for cases like this), so if it's multipart we return a WAMultipartBody or a WASimpleBody (names TBD) .

Anything else could be done as a workaround, like putting each "part" in the postFields, but if we made it this far without supporting it, I'd do it right from the beginning.