echo "HTTP/1.1 100 Continue" before any response data to downstream

Hello!

Recently I found some HTTP client (like curl) will complain "Illegal or missing hexadecimal sequence in chunked-encoding" when sending request to OpenResty which has some configurations like this:

location / {
    content_by_lua_block {
        ngx.print("hello")
    }
}

Sends request like this:

curl -v http://127.0.0.1:8080/ --upload-file /path/to/file

When I discard the request body explicitly (ngx.req.discard_body). Everything is OK.

I'm not sure whether this is the callers' responsibility to discard the request body explicitly. Or ngx_lua can do this implicitly (send HTTP/1.1 100 Continue before any data). What's your opinion?

Reproduce the issue with the shown curl --upload-file request and the content_by_lua_block using ngx.print, then compare it with the explicit ngx.req.discard_body case. Read the request-body and response handling entry points around these APIs and clarify the expected HTTP behavior; done means an agreed handling path with a regression test for the reported client failure.