In SQL Developer 4.0 EA 1, my User Defined Extension of type "Editor" started having multiple tabs show up in the PL/SQL editor window, rather than having just one tab:
<item type="editor" node="PlSqlBaseNode" vertical="false">
<![CDATA[SELECT object_type, line, error_type, message, text
FROM TABLE(sysadmin.reports.reviewCode(:OBJECT_OWNER, :OBJECT_NAME, :OBJECT_TYPE))
ORDER BY line NULLS FIRST]]>
There was only one tab in SQL Developer 3....
Another bug, somewhat related to above: when editing source in a PL/SQL window, you can highlight the text of another PL/SQL object, like a package, and use Popup Describe to bring up its source code. But, when an Editor user defined extension is in place, like one above, rather than getting the source code in the popup window, you only get the user defined extension. Can this be fixed, too (SQL Developer 3 had the same bug).