Curl: Improve Accept-Encoding comment #3215
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jtojnar
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Apr 13, 2024
While researching how the `decode_content` option is meant to be used and looking into the Guzzle source code I stumbled over this part of the code, because it was non-obvious to me that providing an empty string to `CURLOPT_ENCODING` does not *disable* the decoding, but instead enables *all* decoders.
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guzzle@1d46cec tried to improve the comment but the new content implies an empty header will be sent. That is not the case. Quoting from <https://curl.se/libcurl/c/CURLOPT_HTTPHEADER.html>: If you add a header with no content as in 'Accept:' (no data on the right side of the colon), the internally used header is disabled/removed. Let’s clarify the point is removing the header to get the default '*' <https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding#sect2>: *: Matches any content encoding not already listed in the header. This is the default value if the header is not present. This directive does not suggest that any algorithm is supported but indicates that no preference is expressed. As that was probably intended by the original change that introduced this: guzzle@1a9ad6b
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Guzzle does not send `Accept-Encoding` header by default. That is equivalent to sending `Accept-Encoding: *`: https://www.rfc-editor.org/rfc/rfc9110#field.accept-encoding> Most servers will probably return an uncompressed body in response to that, which can be considered wasteful, and can trigger crawler detection systems: #1481 Others might even opt to use a compression method that is not supported by the system (e.g. when libcurl is not compiled with brotli support). Let’s force Guzzle to let curl send `Accept-Encoding` header reflecting which compression methods it supports: guzzle/guzzle#3215
This was referenced Apr 13, 2024
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1d46cec tried to improve the comment but the new content implies an empty header will be sent.
That is not the case. Quoting from https://curl.se/libcurl/c/CURLOPT_HTTPHEADER.html:
Let’s clarify the point is removing the header to get the default '*'
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding#sect2:
As was probably intended by the original change that introduced this: 1a9ad6b