HTTP contacts proxy when asked to get localhost URL despite this making no sense and no_proxy envvar forbids it

[dlakelan]

Julia 1.7.0-beta4
HTTP.jl 0.9.13

When using WGLMakie it uses HTTP to attempt to access a URL that points to the localhost 127.0.0.1, HTTP decides to request this URL through the proxy. It seems to me HTTP should never contact a proxy for a request pointing at the localhost (either the name "localhost" or any ipv4 in "127.0.0.0/8" or the Ipv6 "::1" ). However it should especially not do this because I have listed 127.0.0.0/8 in the no_proxy and NO_PROXY environment variables:

julia> scatter(rand(4))
Error showing value of type Makie.FigureAxisPlot:
ERROR: HTTP.ExceptionRequest.StatusError(503, "GET", "http://127.0.0.1:9284/assetserver/65c7b14432db03331e0c19fc9cc39592adb2b936-JSServe.js", HTTP.Messages.Response:
"""
HTTP/1.1 503 Service Unavailable
Server: squid/4.12
Mime-Version: 1.0
Date: Sun, 29 Aug 2021 18:02:26 GMT
Content-Type: text/html;charset=utf-8
Content-Length: 3786
X-Squid-Error: ERR_CONNECT_FAIL 111
Vary: Accept-Language
Content-Language: en

Here are the relevant environment variables:

no_proxy=127.0.0.0/8,localhost, lan, 10.79.1.0/24, fd56:9122:70e4:1::/64
https_proxy=http://aldproxy.lan:3128
NO_PROXY=127.0.0.0/8,localhost, lan, 10.79.1.0/24, fd56:9122:70e4:1::/64
HTTPS_PROXY=http://aldproxy.lan:3128
HTTP_PROXY=http://aldproxy.lan:3128
http_proxy=http://aldproxy.lan:3128

[quinnj]

Sorry for the slow response here, but here's what I can tell is happening:

• Your no_proxy variable is actually "127.0.0.0/8", which doesn't match the host in the request that was sent ("127.0.0.1"); obviously they're very close and both refer to local loopback addresses, but currently the proxy check is fairly simple and relies on either exact host matching or at least a "dot suffix" match (e.g. noproxy=.google.com will match gmail.google.com)

It does seem from looking around that you never want to proxy localhost requests, so I'm proposing in a forthcoming PR that we ignore proxying when the request host is some form of localhost.

[quinnj]

Fixed in #833