Require $platform in AbstractSchemaManager::__construct()

[morozov]

Q	A
Type	bug
BC Break	yes

Problem Statement

The Connection::getDatabasePlatform() method called from within AbstractSchemaManager::__construct() can throw a DBALException which is neither handled nor declared via @throws.

dbal/src/Schema/AbstractSchemaManager.php

Lines 47 to 54 in 23e8d5d

	/**
	* Constructor. Accepts the Connection instance to manage the schema for.
	*/
	public function __construct(Connection $conn, ?AbstractPlatform $platform = null)
	{
	$this->_conn = $conn;
	$this->_platform = $platform ?? $this->_conn->getDatabasePlatform();
	}

Not only the method throws a non-documented exception, the exception propagates undocumented to Driver::getSchemaManager() which instantiates a schema manager.

Implementations of the Driver interface cannot throw a DBALException because it doesn't belong to this level of abstraction.

Solution

Instantiate the platform in the wrapper layer and avoid the potential exception. The wrapper connection remains as lazy as it was before.

Additional notes

1. Although the code like $this->driver->getSchemaManager($this, $this->getDatabasePlatform()) may look awkward, this weirdness is not caused by this change. The reason is that the wrapper connection is quite a god object, and the very fact that other components depend on it (e.g. instead of a driver connection) is the real issue.
2. No upgrade path is provided. On the one hand, schema managers are supposed to be accessed via the wrapper connection; on the other, adding a new argument to an interface method (even optional) is a BC break.