Jira issue originally created by user mkuckert:
in the method Doctrine\DBAL\Schema\MySqlSchemaManager::getPortableTableColumnDefinition the index "comment" in the array $tableColumn is accessed without ensuring that this index is set. This leads to an Undefined index: comment warning in EALL-environments.
This method is triggered e.g. by the Doctrine\ORM\Tools\SchemaTool getUpdateSchemaSql method.
Comment created by @beberlei:
Can't really explain this, the key has to be existant. This is only called with information from MysqlPlatform#getListTableColumnsSQL().
Comment created by mkuckert:
I've just found the issue. The main problem is the usage of 'DESCRIBE ' . $table; in the getListTableColumnsSQL, if there's no $database set. describe does not return the comment column, but 'show full columns from ' . $table; does.
At the basis of the missing $database value was my own DBAL\Driver implementation not properly returning the currently connected database. So $database was NULL and the alternate code path was executed, so resulting in no comment-property.
Seems like an uncovered code path instead of a bug in a real environment.
Issue was closed with resolution "Fixed"
Special case fixed for 2.4