Don't serialize database connection info

This make sense to me but I don't have much expertise in this area. I think @chx can maybe review the patch.

It's not clear to me why we're serializing anything at all.

What in a PDO/Connection object can be serialized/unserialized?

All we should need is a pointer to the connection to use (pseudo code):

function serialize() {
  return array('key' => $this->key, 'target' => $this->target);
}
function unserialize($serialized) {
  $info = unserialize($serialized);
  $this->key = $info['key'];
  $this->target = $info['target'];
  // Most ideally though, instead:
  $this = Database::getConnection($info['key'], $info['target']);
}

Perhaps that means that we shouldn't pass around actual PDO connection objects, but wrapper objects instead?

What in a PDO/Connection object can be serialized/unserialized?

Note: The connection object no longer extends the PDO connection but wraps it, but yeah

+++ b/core/lib/Drupal/Core/Database/Connection.php
@@ -1249,7 +1249,7 @@ public function quote($string, $parameter_type = \PDO::PARAM_STR) {
-    unset($connection->connection, $connection->schema, $connection->driverClasses);
+    unset($connection->connection, $connection->connectionOptions, $connection->schema, $connection->driverClasses);

For example things like the prefix also depends on the settings.php and driver_class

Does #9 mean this needs work? Patch in #7 still applies.

Added a related issue

@olli
Its great that you found out this problem, good catch!

Expanded the test coverage and covered the additional properties.

+++ b/core/modules/system/src/Tests/Database/ConnectionUnitTest.php
@@ -235,6 +235,11 @@ public function testConnectionSerialization() {
+    $not_serialized_properties = ['connection', 'connectionOptions', 'schema', 'prefixes', 'prefixReplace', 'driverClasses'];
+    foreach ($not_serialized_properties as $property) {
+      $this->assertIdentical(FALSE, strpos($serialized, $property));
+    }

This is a little weak test, but given that both connection and connectionOptions are in there and it passes it _should_ be okay.

Might be better to check for it with '' to at least delimit properly.

Leaving at code needs review for now, but tending to RTBC.

That is a good idea.

On top of that I also wrote a test which actually changes the db settings under the hood and ensure they change after the serialize().

Great test! RTBC - if tests pass!

Thank you!

Nice find. Committed/pushed to 8.0.x, thanks!