Add Tag Dialog: Corrupt key/value added silently with "Recent tags with existing key" enabled

[skyper]

What steps will reproduce the problem?

1. Create new layer
2. Add a node (A) and select it
3. Open Add Tag Dialog and set "Recent tags with existing key" in context menu to "enable"
4. Add tag crossing=uncontrolled to A
5. Add another node (B) and select it
6. Add tags crossing=unmarked and crossing:barrier=no to B
7. select A and open Add Tag Dialog
8. double click on crossing=unmarked

What is the expected result?

The warning about overwriting an existing tag and crossing=unmarked on A after "OK"

What happens instead?

crossing:barrier=unmarked is silently added to A

Please provide any additional information below. Attach a screenshot if possible.

Might be a regression. Mark this as critical as adding corrupt tags is bad.

Tried to save it into a session but the add tag history is not saved.

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-02-12 00:06:43 +0100 (Wed, 12 Feb 2020)
Revision:15845
Build-Date:2020-02-12 02:30:56
URL:https://josm.openstreetmap.de/svn/trunk

[GerdP]

deleted, I skipped step 3. Sorry for the noise.

[skyper]

Best is, to disable "Recent tags with existing key" to be on the save side.

[simon04]

In 15885/josm:

fix #18709 - Add Tag Dialog: disable auto completion during use of recent tags