Malformed multipart/form-data upload - koa servers are unable to process it

[dylanpyle]

I'm going to close this immediately, since I haven't conclusively isolated this to React Native, but figured I should document it in case someone else hits this behavior.

There seems to be some sort of incompatibility between the multipart/form-data request generated by React Native's XHR and fetch implementations, and the request body expected by all the koa middleware's I've tested (koa-body, koa-better-body, koa-multer). This causes the server to silently fail to parse the body, about 50-75% of the time.

It doesn't seem to be a race condition or similar — replaying the same requests will deterministically either succeed or fail, depending on the request body.

Here's a request that fails:
headers
body

And one that succeeds:
headers
body

The only client I found that caused this specific failure mode was the JavaScript XHR / fetch API in React Native. I haven't figured out whether the misbehavior here is on the client or server, but I've managed to avoid it by switching my client to use RNFetchBlob instead.

Cross-post: koajs/koa-body#45

[dylanpyle]

Turns out this was the same issue as #11342 — now resolved!