Allow HTTP::Client to use ipv6 addresses (crystal-lang#6147)

Fixes crystal-lang#5514

spec/std/http/client/client_spec.cr

@@ -121,6 +121,16 @@ module HTTP
       end
     end
 
+    it "sends the host header ipv6 with brackets" do
+      server = HTTP::Server.new do |context|
+        context.response.print context.request.headers["Host"]
+      end
+      address = server.bind_unused_port "::1"
+      spawn { server.listen }
+
+      HTTP::Client.get("http://[::1]:#{address.port}/").body.should eq("[::1]:#{address.port}")
+    end
+
     it "doesn't read the body if request was HEAD" do
       resp_get = TestServer.open("localhost", 0, 0) do |server|
         client = Client.new("localhost", server.local_address.port)

spec/std/uri_spec.cr

@@ -19,6 +19,7 @@ end
 describe "URI" do
   assert_uri("http://www.example.com", scheme: "http", host: "www.example.com")
   assert_uri("http://www.example.com:81", scheme: "http", host: "www.example.com", port: 81)
+  assert_uri("http://[::1]:81", scheme: "http", host: "[::1]", port: 81)
   assert_uri("http://www.example.com/foo", scheme: "http", host: "www.example.com", path: "/foo")
   assert_uri("http://www.example.com/foo?q=1", scheme: "http", host: "www.example.com", path: "/foo", query: "q=1")
   assert_uri("http://www.example.com?q=1", scheme: "http", host: "www.example.com", query: "q=1")
@@ -32,6 +33,12 @@ describe "URI" do
   assert_uri("/foo?q=1", path: "/foo", query: "q=1")
   assert_uri("mailto:[email protected]", scheme: "mailto", path: nil, opaque: "[email protected]")
 
+  describe "hostname" do
+    it { URI.parse("http://www.example.com/foo").hostname.should eq("www.example.com") }
+    it { URI.parse("http://[::1]/foo").hostname.should eq("::1") }
+    it { URI.parse("/foo").hostname.should be_nil }
+  end
+
   describe "full_path" do
     it { URI.parse("http://www.example.com/foo").full_path.should eq("/foo") }
     it { URI.parse("http://www.example.com").full_path.should eq("/") }

src/http/client.cr

@@ -651,7 +651,8 @@ class HTTP::Client
     socket = @socket
     return socket if socket
 
-    socket = TCPSocket.new @host, @port, @dns_timeout, @connect_timeout
+    hostname = @host.starts_with?('[') && @host.ends_with?(']') ? @host[1..-2] : @host
+    socket = TCPSocket.new hostname, @port, @dns_timeout, @connect_timeout
     socket.read_timeout = @read_timeout if @read_timeout
     socket.sync = false
     @socket = socket

src/uri.cr

@@ -119,6 +119,16 @@ class URI
   def initialize(@scheme = nil, @host = nil, @port = nil, @path = nil, @query = nil, @user = nil, @password = nil, @fragment = nil, @opaque = nil)
   end
 
+  # Returns the host part of the URI and unwrap brackets for IPv6 addresses.
+  #
+  # ```
+  # URI.parse("http://[::1]/bar").hostname # => "::1"
+  # URI.parse("http://[::1]/bar").host     # => "[::1]"
+  # ```
+  def hostname
+    host.try { |host| host.starts_with?('[') && host.ends_with?(']') ? host[1..-2] : host }
+  end
+
   # Returns the full path of this URI.
   #
   # ```