Frankly, I am not sure it's a bug or by design. Anyways, you will do a best judgement. I set up a non hideable column with the columns group. I would expect this non hidable column always appears when its parent group column appears. Though there is a scenario to get the group column shown, but its child non hideable column hidden. Please follow the steps to reproduce the issue.
Steps to reproduce the problem:
Run the code sample
Go to the header Columns menu and uncheck "Group"
Then check the "Test2" or "Test3"
The result that was expected:
I would expect the non hidable "Test1" column appear as well.
It is easy to implement the behavior that I need. Just set up a show listener for the Group column where forcibly show the Test1 column. But the reason I have posted the thread is ensuring it's a bug or by design.
I think the group should still be hideable unless you explicitly add hideable="false" to the group header. What the above example should mean is that if the group is displayed then the column that is not hideable should always be shown.