added support for rubies between 2.1 and 2.5 (polyfills)

lib/httpx.rb

@@ -2,6 +2,8 @@
 
 require "httpx/version"
 
+require "httpx/extensions"
+
 require "httpx/errors"
 require "httpx/callbacks"
 require "httpx/loggable"

lib/httpx/extensions.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+unless String.method_defined?(:+@)
+  # Backport for +"", to initialize unfrozen strings from the string literal.
+  #
+  module LiteralStringExtensions
+    def +@
+      frozen? ? dup : self
+    end
+  end
+  String.__send__(:include, LiteralStringExtensions)
+end
+
+unless Numeric.method_defined?(:positive?)
+  # Ruby 2.3 Backport (Numeric#positive?)
+  #
+  module PosMethods
+    def positive?
+      self > 0
+    end
+  end
+  Numeric.__send__(:include, PosMethods)
+end
+unless Numeric.method_defined?(:negative?)
+  # Ruby 2.3 Backport (Numeric#negative?)
+  #
+  module NegMethods
+    def negative?
+      self < 0
+    end
+  end
+  Numeric.__send__(:include, NegMethods)
+end

lib/httpx/io.rb

@@ -139,9 +139,12 @@ module HTTPX
   end
 
   class SSL < TCP
+    TLS_OPTIONS = OpenSSL::SSL::SSLContext.instance_methods.include?(:alpn_protocols) ? 
+        { alpn_protocols: %w[h2 http/1.1] } : {}
+
     def initialize(_, _, options)
       @ctx = OpenSSL::SSL::SSLContext.new
-      @ctx.set_params(options.ssl)
+      @ctx.set_params(TLS_OPTIONS.merge(options.ssl))
       super
       @state = :negotiated if @keep_open
     end

lib/httpx/options.rb

@@ -41,7 +41,7 @@ module HTTPX
       defaults = {
         :debug                    => ENV.key?("HTTPX_DEBUG") ? $stderr : nil,
         :debug_level              => (ENV["HTTPX_DEBUG"] || 1).to_i,
-        :ssl                      => { alpn_protocols: %w[h2 http/1.1] },
+        :ssl                      => {},
         :http2_settings           => { settings_enable_push: 0 },
         :fallback_protocol        => "http/1.1", 
         :timeout                  => Timeout.new,

lib/httpx/plugins/proxy/socks4.rb

@@ -33,7 +33,8 @@ module HTTPX
               throw(:called)
             else
               response = ErrorResponse.new("socks error: #{status}", 0) 
-              while (req, _ = @pending.shift)
+              until @pending.empty?
+                req, _ = @pending.shift
                 emit(:response, req, response)
               end
             end

lib/httpx/plugins/proxy/socks5.rb

@@ -89,7 +89,8 @@ module HTTPX
 
           def on_error_response(error)
             response = ErrorResponse.new(error, 0) 
-            while (req, _ = @pending.shift)
+            until @pending.empty?
+              req, _ = @pending.shift
               emit(:response, req, response)
             end
           end

test/http2_test.rb

@@ -17,7 +17,9 @@ class HTTP2Test < HTTPTest
   include Plugins::FollowRedirects
   include Plugins::Cookies
   include Plugins::Compression
-  include Plugins::PushPromise
+  if OpenSSL::SSL::SSLContext.instance_methods.include?(:alpn_protocols)
+    include Plugins::PushPromise
+  end
 
   private
 

test/options_test.rb

@@ -65,7 +65,7 @@ class OptionsSpec < Minitest::Test
       :body_threshold_size => 114_688,
       :form               => {:bar => "bar"},
       :timeout            => Timeout.new,
-      :ssl                => {:foo => "bar", :alpn_protocols => %w[h2 http/1.1] },
+      :ssl                => {:foo => "bar" },
       :http2_settings     => { :settings_enable_push => 0 },
       :fallback_protocol  => "http/1.1",
       :headers            => {"Foo" => "foo", "Accept" => "xml", "Bar" => "bar"},

test/support/requests/io.rb

@@ -23,7 +23,7 @@ module Requests
       TCPSocket.new(uri.host, uri.port)
     when "https"
       ctx = OpenSSL::SSL::SSLContext.new
-      ctx.alpn_protocols = %w[h2 http/1.1]
+      ctx.alpn_protocols = %w[h2 http/1.1] if ctx.respond_to?(:alpn_protocols)
       sock = OpenSSL::SSL::SSLSocket.new(TCPSocket.new(uri.host, uri.port), ctx)
       sock.hostname = uri.host
       sock.sync_close = true

test/support/requests/response_body.rb

@@ -38,7 +38,7 @@ module Requests
         attr_reader :file
 
         def initialize(response, **)
-          @file = Tempfile.new
+          @file = Tempfile.new("httpx-test")
         end
 
         def write(data)