Merge branch '6.0' into 6.1

* 6.0:
  [DI] fix tests
  [FrameworkBundle] fix merge
  [FrameworkBundle] Filter out trans paths that are covered by a parent folder path
  [Form] fix tests
  [Serializer] Fixed framework.serializer.default_context is not working for JsonEncoder
  [Ldap] Do not run ldap_set_option on failed connection
  Correct compare float data
  Bugfix: add \UnitEnum as a result of get() method
  Fix AbstractFormLoginAuthenticator return types (fixes #47571).
  Run composer with --ignore-platform-req=php+
  [FrameworkBundle] Fix a phpdoc in mailer assertions

Author: nicolas-grekas

Adapter/ExtLdap/Connection.php

@@ -155,18 +155,18 @@ private function connect()
             }
         }
 
-        $this->connection = ldap_connect($this->config['connection_string']);
+        if (false === $connection = ldap_connect($this->config['connection_string'])) {
+            throw new LdapException('Invalid connection string: '.$this->config['connection_string']);
+        } else {
+            $this->connection = $connection;
+        }
 
         foreach ($this->config['options'] as $name => $value) {
             if (!\in_array(ConnectionOptions::getOption($name), self::PRECONNECT_OPTIONS, true)) {
                 $this->setOption($name, $value);
             }
         }
 
-        if (false === $this->connection) {
-            throw new LdapException('Could not connect to Ldap server: '.ldap_error($this->connection));
-        }
-
         if ('tls' === $this->config['encryption'] && false === @ldap_start_tls($this->connection)) {
             throw new LdapException('Could not initiate TLS connection: '.ldap_error($this->connection));
         }