passing a flag for resolvers, where you can choose to use cache or not, which is helpful for tests

lib/httpx/options.rb

@@ -61,6 +61,7 @@ module HTTPX
         :transport_options => nil,
         :persistent => false,
         :resolver_class => (ENV["HTTPX_RESOLVER"] || :native).to_sym,
+        :resolver_options => { cache: true },
       }
 
       defaults.merge!(options)

lib/httpx/resolver/https.rb

@@ -158,7 +158,7 @@ module HTTPX
           next unless connection # probably a retried query for which there's an answer
 
           @connections.delete(connection)
-          Resolver.cached_lookup_set(hostname, addresses)
+          Resolver.cached_lookup_set(hostname, addresses) if @resolver_options.cache
           emit_addresses(connection, addresses.map { |addr| addr["data"] })
         end
       end

lib/httpx/resolver/native.rb

@@ -237,7 +237,7 @@ module HTTPX
           end
         else
           @connections.delete(connection)
-          Resolver.cached_lookup_set(connection.origin.host, addresses)
+          Resolver.cached_lookup_set(connection.origin.host, addresses) if @resolver_options.cache
           emit_addresses(connection, addresses.map { |addr| addr["data"] })
         end
       end

lib/httpx/resolver/resolver_mixin.rb

@@ -38,7 +38,7 @@ module HTTPX
       def early_resolve(connection, hostname: connection.origin.host)
         addresses = connection.addresses ||
                     ip_resolve(hostname) ||
-                    Resolver.cached_lookup(hostname) ||
+                    (@resolver_options.cache && Resolver.cached_lookup(hostname)) ||
                     system_resolve(hostname)
         return unless addresses
 

lib/httpx/resolver/system.rb

@@ -14,10 +14,13 @@ module HTTPX
 
     def initialize(options)
       @options = Options.new(options)
-      roptions = @options.resolver_options
+      @resolver_options = Resolver::Options.new(@options.resolver_options)
       @state = :idle
-      @resolver = Resolv::DNS.new(roptions.nil? ? nil : roptions)
-      @resolver.timeouts = roptions[:timeouts] if roptions
+      resolv_options = @resolver_options.to_h
+      timeouts = resolv_options.delete(:timeouts)
+      resolv_options.delete(:cache)
+      @resolver = Resolv::DNS.new(resolv_options.empty? ? nil : resolv_options)
+      @resolver.timeouts = timeouts if timeouts
     end
 
     def closed?