Add support for footway=traffic_island in the validator

[bxl-forever]

What steps will reproduce the problem?

1. Create a highway=footway with footway=traffic_island
2. Upload
3. Validator warning: "Value of footway should either be access_aisle, crossing or sidewalk.[…]"

What is the expected result?

footway=traffic_island is now an established tag and has been documented in the wiki.
It should be added to the list of correct values for footway:* and not trigger a warning.
Thanks.

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

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2022-01-02 21:24:43 +0100 (Sun, 02 Jan 2022)
Revision:18360
Build-Date:2022-01-02 20:26:19
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (18360 en) Linux Arch Linux
Memory Usage: 920 MB / 3924 MB (230 MB allocated, but free)
Java version: 11.0.14.1+1, Oracle Corporation, OpenJDK 64-Bit Server VM
[redacted for privacy]

[skyper]

Well, the three supported values are approved. All other including traffic_island are not even mentioned on ​key:footway but, please, do not simply add them to the list without indication between approved values and values only in use, thanks. Best would be a proposal for the new values.

Regarding traffic_island I see an overlap with crossing which should be clarified. Additionally, numbers of the value are currently quite low with 1534 objects or 0.03%.

At the moment, I can propose to change the wording of the warning like Uncommon value … or even split it into two, one for the actual deprecated values and one for uncommon values.

[JeroenHoek]

We can add traffic_island to key:footway; with over 1500 uses that is fair enough by now.

For this issue I have already submitted a patch in #21235. That was put on hold in order to clarify the sidewalk=none deprecation. Now that that is resolved, that patch could be reconsidered.

The issue here is not that other values for footway=* should all be approved first, but that JOSM shouldn't apply a whitelist to a key that essentially supports user-defined values. What JOSM should do (and does) is check the blacklist for a few values that should be used with sidewalk=* instead. My patch adds footway=separate to the blacklist for that purpose.

[skyper]

Closed as duplicate of #21235.
Right, I forgot about #21235. For JOSM core 1500 uses is low.

[JeroenHoek]

For JOSM core 1500 uses is low.

Too low to actively support it via core presets, I can somewhat agree to that (although I would draw the line at 1000 for many tag-values). But it seems quite high enough (properly documented too) to stop warning people that they may have used an invalid value. It is not an obvious misspelling or misused value (like left which tends to mean that someone used footway=left instead of sidewalk=left).

Whitelisting a user-defined key actively harms adoption of new values; whereas if I decide to create a new highway=floob now I get no warning at all. As noted in #21235, that whitelist is no longer needed now that the active checks on actual invalid footway=* values (left, right, etc.) are there.