Set proxies according to the *_PROXY environment variables

[hkalexling]

The [protocol]_PROXY and NO_PROXY environment variables are commonly used to configure proxies in applications. Wget and Emacs are two examples. Python's requests library also respects HTTP_PROXY and HTTPS_PROXY out of the box.

It would be great if we could have a helper method like HTTP::Proxy::Client.use_env that would do the followings

1. When used, it would automatically load the appropriate settings from ENV and create the corresponding HTTP::Proxy::Client objects.
2. It would then monkey-patch the HTTP::Client class in the standard library so that the clients use the appropriate proxies in all requests.

Here's an example implementation I used in my project. I will be happy to submit a PR if you think it's a good idea.

[kojix2]

Looks good for me! :+1:

However, the get_proxy method could return nil, resulting in the following error

In src/utils/proxy.cr:33:26

 33 | client.set_proxy get_proxy uri
                       ^--------
Error: expected argument #1 to 'HTTP::Client#set_proxy' to be HTTP::Proxy::Client, not (HTTP::Proxy::Client | Nil)

This error can of course be easily avoided

        if prxy = get_proxy(uri)
          client.set_proxy prxy
        end

Thanks!

[mamantoha]

Hi @hkalexling @kojix2 I apologize for the delay in addressing this issue. Could you please create a pull request for this? I would greatly appreciate it. Thank you.

[kojix2]

Long time no see.

For some reason, the above code didn't work on Crest. I haven't looked into why. I wrote a workaround like this:

module Crest
  class Request
    def initialize(
      method : Symbol,
      url : String,
      form = {} of String => String,
      **args
    )
      previous_def
      url = URI.parse(@url)
      no_proxy = ENV["no_proxy"]? || ENV["NO_PROXY"]?
      return if no_proxy && no_proxy.split(",").includes?(url.host)
      key = "#{url.scheme}_proxy"
      proxy_ = ENV[key.downcase]? || ENV[key.upcase]?
      return if proxy_.nil?
      uri = URI.parse proxy_
      @p_addr = uri.host
      @p_port = uri.port
      @p_user = uri.user
      @p_pass = uri.password
      set_proxy!(@p_addr, @p_port, @p_user, @p_pass)
    end
  end
end

However, this workaround breaks as soon as the signature of the Crest::Request#initialize method changes. It would be better to handle it on the https_proxy side.

[mamantoha]

@kojix2 Which specific piece of code are you referring to?