Hello,
SQL Developer version: 21.4.2
Windows 7 / 10
SQL Developer's GUI may hang after closing the source and/or destination connections from a not-yet-closed Database Diff report, if the passwords are not saved along with the connections.
If the passwords are saved along with the connections, apparently the source connection will be reopened automatically. If they are not, SQL Developer will prompt for the password of the source connection, or at least attempt to do so.
The above screenshot is from a Windows 7 box; the Connection Information dialog does not even get entirely displayed before the GUI freezes. Things seem to go a little better on Windows 10: the Connection Information dialog opens and it works, unless the ESC key is pressed in order to prevent from the connection reopening: at that stage, the GUI freezes.
Bottom line: seemingly the Database Diff report tool requires its source and/or destination connections to remain open, hence it should be closed before these connections; doing it the other way around may result in the GUI hanging.
Thread dump
sqldev-full_thread_dump.txt.gz (5.46 KB)(From the above test using Windows 7.)
Regards,