request.GetBody() breaks the request object

[bcomnes]

I tracked down a bug in the implementation of request.GetBody I think.

I wrote a failing test to demonstrate the bug:

https://gist.github.com/bcomnes/4ffddcd270e8721267efa4b9e2ed89b8#file-http_test-go

The example is pretty contrived, but if you use a custom roundTripper and get ahold of the req object generated by go-openapi before you give it to transport.RoundTrup and call req.GetBody, it causes the client operation ClientRequestWriterFunc to write out any BodyParam to the req.Body again, doubling/tripling the req.Body etc. The length of the req.Body basically grows to n x req.ContentLength where n is the number of times you call req.GetBody before reading req.Body.

At this point the req object is toast, since the length of the Body no longer matches the ContentLengh. Passing it to transport.RoundTrip fails with this error:

'https://github.com/golang/go/blob/61170f85e62f1326d42c4dbd8aa17ab4a1305a87/src/net/http/transfer.go#L387-L389

The contents of the Body returned by req.GetBody is perfect, even if you call req.GetBody multiple times. Its only req.Body that is affected. This only applies when you have body parameters.

Bug

Calling .GetBody() should not cause the Body to be written to again by ClientRequestWriterFunc

Possible resolution

If you have any ideas of where this is happening, I would love to hear them. I would like to PR the failing test for you, and start hunting down an actual fix. I am open to any suggestions if you have them.

[casualjim]

I think this is the reason: https://github.com/go-openapi/runtime/blob/master/client/request.go#L216

The first 2 options that come to mind are:

• the buffer needs to be reset on every call to get body, or at least it should start reading after the currently captured offset
• wrap the entire thing in a sync.Once so that it only executes once which is probably closer to intent

[bcomnes]

Very cool! Thank you for those. I am willing to try to find and PR a fix in, unless you prefer to do it.

[casualjim]

Cool, looking forward to your PR