fix for loop on resolution and retry on new connection

A certain behaviour was observed, when performing some tests using the
hackernews script, where after a failed request on a non-initiated
connection, a new DNS resolution would be emitted, although the
connection still had other IPs to try on. This led to a cascading
behaviour where the DNS response would fill up the connection with the
same repeated IPs and trigger coalescing, which would loop indefinitely
after emitting the resolve event.

This was fixed by not allowing DNS resolution on already resolved names,
to propagate to connections which already contain the advertised IPs.

This seems to address the github issue 5, which description matches the
observed behaviour.

lib/httpx/extensions.rb

@@ -83,22 +83,41 @@ module HTTPX
   end
 
   module ArrayExtensions
-    refine Array do
+    module FilterMap
+      refine Array do
 
-      def filter_map
-        return to_enum(:filter_map) unless block_given?
+        def filter_map
+          return to_enum(:filter_map) unless block_given?
 
-        each_with_object([]) do |item, res|
-          processed = yield(item)
-          res << processed if processed
+          each_with_object([]) do |item, res|
+            processed = yield(item)
+            res << processed if processed
+          end
         end
       end unless Array.method_defined?(:filter_map)
+    end
 
-      def sum(accumulator = 0, &block)
-        values = block_given? ? map(&block) : self
-        values.inject(accumulator, :+)
+    module Sum
+      refine Array do
+        def sum(accumulator = 0, &block)
+          values = block_given? ? map(&block) : self
+          values.inject(accumulator, :+)
+        end
       end unless Array.method_defined?(:sum)
     end
+
+    module Intersect
+      refine Array do
+        def intersect?(arr)
+          if size < arr.size
+            smaller = self
+          else
+            smaller, arr = arr, self
+          end
+          (array & smaller).size > 0
+        end
+      end unless Array.method_defined?(:intersect?)
+    end
   end
 
   module IOExtensions

lib/httpx/plugins/compression.rb

@@ -72,7 +72,7 @@ module HTTPX
       end
 
       module ResponseBodyMethods
-        using ArrayExtensions
+        using ArrayExtensions::FilterMap
 
         attr_reader :encodings
 

lib/httpx/pool.rb

@@ -7,7 +7,7 @@ require "httpx/resolver"
 
 module HTTPX
   class Pool
-    using ArrayExtensions
+    using ArrayExtensions::FilterMap
     extend Forwardable
 
     def_delegator :@timers, :after

lib/httpx/resolver/multi.rb

@@ -6,7 +6,7 @@ require "resolv"
 module HTTPX
   class Resolver::Multi
     include Callbacks
-    using ArrayExtensions
+    using ArrayExtensions::FilterMap
 
     attr_reader :resolvers
 

lib/httpx/resolver/resolver.rb

@@ -8,6 +8,8 @@ module HTTPX
     include Callbacks
     include Loggable
 
+    using ArrayExtensions::Intersect
+
     RECORD_TYPES = {
       Socket::AF_INET6 => Resolv::DNS::Resource::IN::AAAA,
       Socket::AF_INET => Resolv::DNS::Resource::IN::A,
@@ -48,6 +50,10 @@ module HTTPX
       addresses.map! do |address|
         address.is_a?(IPAddr) ? address : IPAddr.new(address.to_s)
       end
+
+      # double emission check
+      return if connection.addresses && !addresses.intersect?(connection.addresses)
+
       log { "resolver: answer #{connection.origin.host}: #{addresses.inspect}" }
       if @pool && # if triggered by early resolve, pool may not be here yet
          !connection.io &&
@@ -56,8 +62,12 @@ module HTTPX
          addresses.first.to_s != connection.origin.host.to_s
         log { "resolver: A response, applying resolution delay..." }
         @pool.after(0.05) do
-          connection.addresses = addresses
-          emit(:resolve, connection)
+          # double emission check
+          unless connection.addresses && addresses.intersect?(connection.addresses)
+
+            connection.addresses = addresses
+            emit(:resolve, connection)
+          end
         end
       else
         connection.addresses = addresses

lib/httpx/response.rb

@@ -310,9 +310,12 @@ module HTTPX
 
   class ErrorResponse
     include Loggable
+    extend Forwardable
 
     attr_reader :request, :error
 
+    def_delegator :@request, :uri
+
     def initialize(request, error, options)
       @request = request
       @error = error

lib/httpx/transcoder/body.rb

@@ -9,7 +9,7 @@ module HTTPX::Transcoder
     module_function
 
     class Encoder
-      using HTTPX::ArrayExtensions
+      using HTTPX::ArrayExtensions::Sum
       extend Forwardable
 
       def_delegator :@raw, :to_s

sig/response.rbs

@@ -96,6 +96,7 @@ module HTTPX
   class ErrorResponse
     include _Response
     include Loggable
+    extend Forwardable
 
     @options: Options
     @error: Exception
@@ -104,6 +105,8 @@ module HTTPX
 
     def status: () -> (Integer | _ToS)
 
+    def uri: () -> URI::Generic
+
     private
 
     def initialize: (Request, Exception, options) -> untyped