Unknown construction=* values hide construction roads

[imagico]

Similar to #4568 we have another weird catch-all interpretation of tags in display of construction roads. When a highway=construction is tagged with a construction value we do not explicitly interpret like construction=foo we do not render them - while we do render them if there is no construction=* tagged at all:

Reason is this:

openstreetmap-carto/style/roads.mss

Line 1227 in 4d1b5ff

[construction = null][zoom >= 14],

As a general principle we tend to ignore unknown tags, i.e. construction=foo should be interpreted as if no construction=* is tagged to allow mappers the freedom to invent new tags without that being punished by us interpreting it as explicitly invalid. Even if we'd want to enforce a limited set of highway types the resulting feedback through hiding is confusing.

[matkoniecz]

another option is hiding bare highway=construction (see #4723)

It is also confusing when highway=construction construction=ant_tunnel will be rendered and highway=ant_tunnel will not be (example hopefully fictional)

[imagico]

Yes, that would be an option. It would however incentivize adding a made up/guessed construction=* value for it to show up in cases where the type of road is - at the construction stage - not possible to determine for the mapper. 221k of 304k highway=construction ways have a construction=* tag.

[mvglasow]

If the type of road cannot be determined during construction, I would suggest tagging the road highway=construction, construction=road. Similar to how highway=road is used for a road of an unknown type, and consistent with how we tag other road types under construction. This hopefully gets rendered (if not, it should).