What should it show as proper message. Did you trash the category and then delete it or did you trash it only. If you trash and do not delete, the category is still inside the database. It is just set to trashed. If you want to erase it you need to use the search tools inside the category manager and inside the dropdown - Select Status - choose trashed as status. You will see here that the category is still there. If so choose the category and click on Empty Trash. You can now create a new one with same name and that message will not show up.

@franzpeter
I know Joomla very well, I know trash/empty trash and all in very much deep. My suggestion was for the million of other users, who could face that issue.

I and my less-than-knowledgeable admin clients get frustrated by this.
Changing the message to

a Trashed category has the same alias and must be deleted first.

or

a Published category has the same alias.

would be extremely helpful and would increase Joomla's uptake by
non-technical people.

Cheers
Paul

On Thursday, April 23, 2015, Aasim Ali > wrote:

@franzpeter https://github.com/franzpeter
I know Joomla very well, I know trash/empty trash and all in very much
deep. My suggestion was for the million of other users, who could face that
issue.

—
Reply to this email directly or view it on GitHub
#6823 (comment).

I wouldn't make different messages depending on the publish state of the existing category. But it may be indeed helpful to improve the message so it gives a hint to check the trashed items.
@brianteeman What do you think?

I don't have a computer at the moment (finally getting ti repaired) I will
try to remember to take a look next week when I get it back but if I don't
comment please remind me. With age comes wisdom but also a lack of memory

Hi Brian and issue tracker friends. It's the first time I post, so forgive me if I violate any rules. I just want 2 things:

1. To agree with this post in that the more descriptive error message would be helpful for newbs. It took me a little while to figure out that the trashed things remain and the trash must be emptied in order to re-use the aliases.
2. I also want to add a related issue (wasn't sure whether to poste to this thread or open a new one...) I'm using joomla 3.4.1 in an xampp server and I cannot empty the trashed categories from the Category Manager Trash. I select all the trashed categories, then click on empty trash, but nothing happens. No success message, no error message, nothing. The screen just blinks and the trashed categories remain visible.

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   _{This comment was created with the J!Tracker Application at issues.joomla.org/joomla-cms/6823.}

Please see #6863

@inesrosas please create a new issue for your second point