[Patch] There should be a validator warning for the deprecated key building:roof

[goodidea]

The key building:roof=* is deprecated (according to the wiki in favor of roof:material=*, see ​https://wiki.openstreetmap.org/wiki/Key:building:roof). There should be a validator warning for this deprecated key.

A note: a saw this key not only with material values, but also with roof shape values, e.g. building:roof=flat (or gabled/hipped/...). According to taginfo, espacially the tag building:roof=flat is still used 10627 times! See ​https://taginfo.openstreetmap.org/keys/building:roof#values. So maybe the warning text of the validator should not only specify roof:material=* as a replacement (like in the wiki), but also roof:shape=* ...

One more note: At the moment there is already a validator warning for another similar deprecated key building:roof:shape=*, see https://josm.openstreetmap.de/changeset/17942/josm.

[taylor.smock]

That looks more like a case for an automated edit. Have you looked into doing that (there are some good practices for that on the wiki)? It does take community buy-in, but will be much faster.

One caveat is that the values may no longer be correct, since buildings tend to be reroofed from time to time.

As an alternative, you can make a maproulette tag fix challenge that changes the tag to match current tagging standards, and have the community fix it.

I'm kind of disinclined to add it to the deprecated list, since it doesn't look like the tag is being actively added.

[goodidea]

Not sure if an automated (mechanical) edit would be good ... I changed today approx. 30 tags in my city (all with building:roof=flat), and at least in 5 cases the roof shape wasn't correct and it was tagged in 2011. I assume the satellite images back then (2011) were not good enough. I saw via Bing, for example, that some of them were gabled (and I also know most of these buildings by sight).

Another problem for a mechanical edit: taginfo shows some values like “pitched” that are not common for roof:shape. And the material values ​​do not always seem to correspond to the current standards for roof:material=*. (By the way, it's also strange that the most common value is building:roof=metal – 136583x – ... metal roofs aren't exactly the most common thing.)

For me, it would have been a big advantage if the JOSM validator would warn about this – I do mappings since a long time and a lot with buildings in my city (and in my region), but I never noticed this tag before – I must have always overlooked it, so I had already added roof:shape=flat to some buildings that already had this building:roof=flat tag. A validator warning would have helped me discover this earlier ... Today I noticed this key for the first time by chance and that's why I wrote this report, because I was a bit surprised by it (and also that there was no validator warning, which is generally the case for deprecated tags).

I don't quite understand why it shouldn't be included in the validator – it's still used 422,178 times. And building:roof:shape=* is also included in the validator, so why not building:roof=*? Seems somehow inconsistent to me.

Regarding usage: the tag history shows increasing usage until 2022, and only since then has it slowly declined – quite slowly (​https://taghistory.raifer.tech/?#***/building%3Aroof/). Maybe other users won't notice it either... And Osmose, for example, doesn't warn about it either (useful in Vespucci) because it uses the JOSM validator for his warnings about deprecated tags as far as I know – i.e. you don't see a warning in Vespucci either. So adding it in the JOSM validator would have a double effect.

Of course, there could be an additional maproulette tag fix challenge, but a validator warning would be helpful in any case – in addition and apart from that (and would probably not be a big effort, I assume).

[skyper]

First task would be to remove building:roof=* from the two external presets for Indonesia: Presets/BuildingsIndonesia and Presets/HOT-PDC_InAWARE_Project_Indonesia.
Maybe some more of tags of these two presets should be checked, too.
I already have added @harrymahar to Cc but I do not have a full email address or user name for Kate Chapman.

Looking at the numbers and it rather slow decrease over the last years, I think the warning would make sense within core. Nevertheless, here is a patch which could be used, wether in core or as an external rule.

/* #24033 */
*[building:roof] {
  throwWarning: tr("{0} is deprecated", "{0.key}");
  suggestAlternative: "roof:material";
  suggestAlternative: "roof:shape";
  group: tr("deprecated tagging");
}