Shorten default string length

- Introduce varcharmax config item, this default eventually should be increased to 255, when MySQL 5.6 support is dropped
- Config item can be kept to retain legacy support
- Only apply to mysql driver, previously was impacting other drivers
- Source true config values, previously was sourcing hard coded "mysql" connection values

config/database.php

@@ -53,16 +53,17 @@ return [
         ],
 
         'mysql' => [
-            'driver'    => 'mysql',
-            'engine'    => 'InnoDB',
-            'host'      => 'localhost',
-            'port'      => 3306,
-            'database'  => 'database',
-            'username'  => 'root',
-            'password'  => '',
-            'charset'   => 'utf8mb4',
-            'collation' => 'utf8mb4_unicode_ci',
-            'prefix'    => '',
+            'driver'     => 'mysql',
+            'engine'     => 'InnoDB',
+            'host'       => 'localhost',
+            'port'       => 3306,
+            'database'   => 'database',
+            'username'   => 'root',
+            'password'   => '',
+            'charset'    => 'utf8mb4',
+            'collation'  => 'utf8mb4_unicode_ci',
+            'prefix'     => '',
+            'varcharmax' => 191,
         ],
 
         'pgsql' => [

modules/system/ServiceProvider.php

@@ -1,5 +1,6 @@
 <?php namespace System;
 
+use Db;
 use App;
 use View;
 use Event;
@@ -84,9 +85,7 @@ class ServiceProvider extends ModuleServiceProvider
     public function boot()
     {
         // Fix UTF8MB4 support for MariaDB < 10.2 and MySQL < 5.7
-        if (Config::get('database.connections.mysql.charset') === 'utf8mb4') {
-            Schema::defaultStringLength(191);
-        }
+        $this->applyDatabaseDefaultStringLength();
 
         // Fix use of Storage::url() for local disks that haven't been configured correctly
         foreach (Config::get('filesystems.disks') as $key => $config) {
@@ -564,4 +563,24 @@ class ServiceProvider extends ModuleServiceProvider
     {
         View::share('appName', Config::get('app.name'));
     }
+
+    /**
+     * Fix UTF8MB4 support for old versions of MariaDB (<10.2) and MySQL (<5.7)
+     */
+    protected function applyDatabaseDefaultStringLength()
+    {
+        if (Db::getDriverName() !== 'mysql') {
+            return;
+        }
+
+        $defaultStrLen = Db::getConfig('varcharmax', null);
+
+        if ($defaultStrLen === null && Db::getConfig('charset') === 'utf8mb4') {
+            $defaultStrLen = 191;
+        }
+
+        if ($defaultStrLen !== null) {
+            Schema::defaultStringLength((int) $defaultStrLen);
+        }
+    }
 }