Requiring OSM attribution at runtime

[opk12]

Motivation

The Quick Start is explicit that the OpenStreetMap attribution is mandatory. In the common case that OSM's official tile server is used, the lib can check at runtime to provide an attribution, to benefit the developer and OSM.

Suggested solution

What about providing a default attribution, or giving an error, if the domain is any of tile.openstreetmap.org or tile.osm.org and the attribution is absent?

Additional context

I am an OSM contributor and hear cases of missing attribution with the OSM official tile server every now and then; so many that a repo was recently set up to keep track of them, and this includes cases where Leaflet is used.

[mourner]

Actually, providing a default OSM attribution when none is provided and tile.openstreetmap.org is used sounds like a neat idea. It's a common pitfall and this seems rather harmless — people who need the attribution to be empty for whatever reason (e.g. attribution is on a different visible part of the page) can do so explicitly by passing attribution: ''. This can be considered a breaking change though. @jonkoops @Falke-Design @IvanSanchez what do you guys think?

[IvanSanchez]

@mourner Given the sheer amount of Leaflet users that (a) are newbies and (b) use OSM tiles, this seems like a nice idea indeed. The cost in terms of codebase size is negligible IMO.

(There is an alternative, which I can call "The OpenLayers Way": provide a L.TileLayer.OSM, a la leaflet-providers. But I think it goes against Leaflet tradition of tile URL templates all around)

Disclaimer: I have been in the OSMF (loooong ago), so I'm understandably biased in favour of OSM.

[matkoniecz]

tile.openstreetmap.org or tile.osm.org

likely the same for a.tile.openstreetmap.org / b.tile.openstreetmap.org / c.tile.openstreetmap.org deprecated addressing ( openstreetmap/operations#737 )

Disclaimer: I am really active in OSM community

[jonkoops]

I think we could parse the URL of the tile-server in general and match it against a couple of known domains:

const url = new URL('https://tile.openstreetmap.org/{z}/{x}/{y}.png');
const osmHosts = ['tile.openstreetmap.org', 'tile.osm.org'];
const isOsmUrl = osmHosts.some((host) => url.hostname.endsWith(host));

[Falke-Design]

I think adding the attribution automatically can be our part to the OSM Community.

This can be considered a breaking change though

Let us add it in v2 and then it is no problem.

const url = new URL('https://tile.openstreetmap.org/{z}/{x}/{y}.png');

Instead of creating a URL object, we could just check if the url-string contains the hosts. Maybe we should create a performance test. If the URL is faster or only slightly slower, let us use the URL object because it is cleaner.

I would suggest to label it as accepted and good first issue Good for newcomers

[IvanSanchez]

Instead of creating a URL object, we could just check if the url-string contains the hosts. Maybe we should create a performance test.

It's a one-off check (when a L.TileLayer is instantiated), so I wouldn't worry about perf issues.

I say URL() plus regexp.

[jieter]

I understand the importance of attribution, but I think adding attribution in the leaflet attribution control is not required. It can also be attributed in another part of the page right?

Would a Leaflet user be able to do that if this change is added?

[matkoniecz]

people who need the attribution to be empty for whatever reason (e.g. attribution is on a different visible part of the page) can do so explicitly by passing attribution: ''.

#9228 (comment)

[opk12]

I understand the importance of attribution, but I think adding attribution in the leaflet attribution control is not required. It can also be attributed in another part of the page right?

Sure, the official OSMF attribution guidelines make it clear that, by the time the user sees the map, she must have already been exposed to the attribution, as we can infer from this:

The base requirement in ODbL is attribution that is “…reasonably calculated to make any Person that uses, views, accesses, interacts with, or is otherwise exposed to the Produced Work aware that Content was obtained from [OpenStreetMap] …”.