Unknown Content-Encoding value and zero-lenght string CURLOPT_ACCEPT_ENCODING

From: Fujii Hironori via curl-library <curl-library_at_lists.haxx.se>
Date: Thu, 28 Oct 2021 16:39:20 +0900

Hi,

Monaco Editor Samples is using their own HTTP server 'yaserver' which sends
an invalid 'Content-Encoding: utf8' header.
<https://github.com/microsoft/monaco-editor-samples>
<https://github.com/alexdima/yaserver>

If I invoke curl command, it reports no error for the unknown encoding.
> curl -v http://localhost:8888/

However, if I invoke curl commnad with '--compressed' switch, it reports
'CURLE_BAD_CONTENT_ENCODING' error.
~~~
$ curl -v --compressed http://localhost:8888/
* Trying 127.0.0.1:8888...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8888 (#0)
> GET / HTTP/1.1
> Host: localhost:8888
> User-Agent: curl/7.68.0
> Accept: */*
> Accept-Encoding: deflate, gzip, br
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Content-Encoding: utf8
< Content-Type: text/html
< Expires: Thu, 28 Oct 2021 07:06:19 GMT
< ETag: e54e50d368dc1cf7edcfd55ca1226c7c
< Content-Length: 5736
< Date: Thu, 28 Oct 2021 07:06:14 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
<
* Unrecognized content encoding type. libcurl understands deflate, gzip, br
content encodings.
* Closing connection 0
curl: (61) Unrecognized content encoding type. libcurl understands deflate,
gzip, br content encodings.
~~~

According to <
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding>
'identity' value "is always considered as acceptable, even if omitted."
Why doesn't curl treat the unknown encoding as identity if
CURLOPT_ACCEPT_ENCODING is set to ""?
I want the zero-length string CURLOPT_ACCEPT_ENCODING to accept both
compressed and non-compressed encodings.

WebKit WinCairo port is using libcurl as the network stack, and it sets
CURLOPT_ACCEPT_ENCODING to "".
So, it can't load the content. However, Google Chrome and Firefox can load
the invalid encoding.

Should WinCairo set the CURLOPT_ACCEPT_ENCODING explicitly to the following
instead of "" ?

> curl_easy_setopt(m_handle, CURLOPT_ACCEPT_ENCODING, "identity, deflate,
gzip, br");

-- Fujii

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Received on 2021-10-28