Change default charset encoding to utf8mb4 for full UTF-8 support

Author: clue

README.md

@@ -175,11 +175,10 @@ authentication. You can explicitly pass a custom timeout value in seconds
 $factory->createConnection('localhost?timeout=0.5');
 ```
 
-By default, the connection uses the `utf8` charset encoding. Note that
-MySQL's `utf8` encoding (also known as `utf8mb3`) predates what is now
-known as UTF-8 and for historical reasons doesn't support emojis and
-other characters. If you want full UTF-8 support, you can pass the
-charset encoding like this:
+By default, the connection provides full UTF-8 support (using the
+`utf8mb4` charset encoding). This should usually not be changed for most
+applications nowadays, but for legacy reasons you can change this to use
+a different ASCII-compatible charset encoding like this:
 
 ```php
 $factory->createConnection('localhost?charset=utf8mb4');
@@ -291,11 +290,10 @@ timeout) like this:
 $factory->createLazyConnection('localhost?idle=0.1');
 ```
 
-By default, the connection uses the `utf8` charset encoding. Note that
-MySQL's `utf8` encoding (also known as `utf8mb3`) predates what is now
-known as UTF-8 and for historical reasons doesn't support emojis and
-other characters. If you want full UTF-8 support, you can pass the
-charset encoding like this:
+By default, the connection provides full UTF-8 support (using the
+`utf8mb4` charset encoding). This should usually not be changed for most
+applications nowadays, but for legacy reasons you can change this to use
+a different ASCII-compatible charset encoding like this:
 
 ```php
 $factory->createLazyConnection('localhost?charset=utf8mb4');

src/Factory.php

@@ -143,11 +143,10 @@ public function __construct(LoopInterface $loop = null, ConnectorInterface $conn
      * $factory->createConnection('localhost?timeout=0.5');
      * ```
      *
-     * By default, the connection uses the `utf8` charset encoding. Note that
-     * MySQL's `utf8` encoding (also known as `utf8mb3`) predates what is now
-     * known as UTF-8 and for historical reasons doesn't support emojis and
-     * other characters. If you want full UTF-8 support, you can pass the
-     * charset encoding like this:
+     * By default, the connection provides full UTF-8 support (using the
+     * `utf8mb4` charset encoding). This should usually not be changed for most
+     * applications nowadays, but for legacy reasons you can change this to use
+     * a different ASCII-compatible charset encoding like this:
      *
      * ```php
      * $factory->createConnection('localhost?charset=utf8mb4');
@@ -183,7 +182,7 @@ public function createConnection(
                 isset($parts['user']) ? rawurldecode($parts['user']) : 'root',
                 isset($parts['pass']) ? rawurldecode($parts['pass']) : '',
                 isset($parts['path']) ? rawurldecode(ltrim($parts['path'], '/')) : '',
-                isset($args['charset']) ? $args['charset'] : 'utf8'
+                isset($args['charset']) ? $args['charset'] : 'utf8mb4'
             );
         } catch (\InvalidArgumentException $e) {
             return \React\Promise\reject($e);
@@ -363,11 +362,10 @@ public function createConnection(
      * $factory->createLazyConnection('localhost?idle=0.1');
      * ```
      *
-     * By default, the connection uses the `utf8` charset encoding. Note that
-     * MySQL's `utf8` encoding (also known as `utf8mb3`) predates what is now
-     * known as UTF-8 and for historical reasons doesn't support emojis and
-     * other characters. If you want full UTF-8 support, you can pass the
-     * charset encoding like this:
+     * By default, the connection provides full UTF-8 support (using the
+     * `utf8mb4` charset encoding). This should usually not be changed for most
+     * applications nowadays, but for legacy reasons you can change this to use
+     * a different ASCII-compatible charset encoding like this:
      *
      * ```php
      * $factory->createLazyConnection('localhost?charset=utf8mb4');

tests/ResultQueryTest.php

@@ -361,7 +361,7 @@ public function testSelectCharsetDefaultsToUtf8()
         $connection->query('SELECT @@character_set_client')->then(function (QueryResult $command) {
             $this->assertCount(1, $command->resultRows);
             $this->assertCount(1, $command->resultRows[0]);
-            $this->assertSame('utf8', reset($command->resultRows[0]));
+            $this->assertSame('utf8mb4', reset($command->resultRows[0]));
         });
 
         $connection->quit();