Use vio_is_connected to check connected state

Author: csfrancis

ext/mysql2/client.c

@@ -26,7 +26,8 @@ static ID intern_brackets, intern_merge, intern_merge_bang, intern_new_with_args
   }
 
 #if defined(HAVE_MYSQL_NET_VIO) || defined(HAVE_ST_NET_VIO)
-  #define CONNECTED(wrapper) (wrapper->client->net.vio != NULL && wrapper->client->net.fd != -1)
+  my_bool vio_is_connected(Vio *vio);
+  #define CONNECTED(wrapper) (wrapper->client->net.vio != NULL && wrapper->client->net.fd != -1 && vio_is_connected(wrapper->client->net.vio))
 #elif defined(HAVE_MYSQL_NET_PVIO) || defined(HAVE_ST_NET_PVIO)
   #define CONNECTED(wrapper) (wrapper->client->net.pvio != NULL && wrapper->client->net.fd != -1)
 #endif

spec/mysql2/client_spec.rb

@@ -573,7 +573,7 @@ def run_gc
       end
       expect do
         @client.query("SELECT SLEEP(1)")
-      end.to raise_error(Mysql2::Error, /Lost connection to MySQL server/)
+      end.to raise_error(Mysql2::Error, 'MySQL client is not connected')
 
       if RUBY_PLATFORM !~ /mingw|mswin/
         expect do
@@ -582,6 +582,19 @@ def run_gc
       end
     end
 
+    it "should detect a closed connection" do
+      connection_id = @client.thread_id
+      Thread.new do
+        sleep(0.1)
+        Mysql2::Client.new(DatabaseCredentials['root']).tap do |supervisor|
+          supervisor.query("KILL #{connection_id}")
+        end.close
+      end
+      expect(@client.query("SELECT 1").first["1"]).to eql(1)
+      sleep(0.2)
+      expect(@client.closed?).to be true
+    end
+
     if RUBY_PLATFORM !~ /mingw|mswin/
       it "should not allow another query to be sent without fetching a result first" do
         @client.query("SELECT 1", async: true)