according to Stof, this bug https://github.com/sensio/SensioGeneratorBundle/issues/21 comes from the doctrine tools implementation:
in the dialog, i first specified that i want a field id of type integer. the result was
Duplicate definition of column 'id' on entity 'Liip\DemoBundle\Entity\Event' in a field or discriminator column mapping.
and no file was created.
The dialog should tell me i can not create a field named id. (Or better ask first if i want my id column named id or something else.)
It would be nice if it would write some file even if its not valid, with a warning on top. As it is, i lost all my work of specifying fields. (Luckily was just playing around)