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max_native_zoom not working for TileLayer

See original GitHub issue

I was trying to serve a local TileLayer that only contains zoom 19 tiles with the following piece of code:

from ipyleaflet import Map, basemap_to_tiles

test = basemap_to_tiles(
    {
        "url": "http://localhost:8000/{z}/{y}/{x}.png",
        "max_zoom":21,
        "min_zoom":19,
        "max_native_zoom":19
    },
)

m = Map(
    center=[38.73855512843848, -9.129069282806583],
    zoom=19,
    max_zoom=21,
    basemap=test,
)
m

without any success, the output is an empty map. I started looking for the problem and I noticed that the request for the tiles was being made for zoom 18, instead of zoom 19, and since I don’t have any I couldn’t load any image.

Went on playing with the source code and once I changed the TileLayer max_native_zoom to 19, now I was getting the request for zoom 19.

class TileLayer(RasterLayer):
      _view_name = Unicode('LeafletTileLayerView').tag(sync=True)
      _model_name = Unicode('LeafletTileLayerModel').tag(sync=True)

      bottom = Bool(True).tag(sync=True)
      url = Unicode('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png').tag(sync=True)
      min_zoom = Int(0).tag(sync=True, o=True)
      max_zoom = Int(18).tag(sync=True, o=True)
      min_native_zoom = Int(0).tag(sync=True, o=True)
      # Had to change max_native zoom directly in the source code from 18 to 19
      # max_native_zoom = Int(18).tag(sync=True, o=True) 
      max_native_zoom = Int(19).tag(sync=True, o=True) 
      tile_size = Int(256).tag(sync=True, o=True)
      attribution = Unicode('Map data (c) <a href="https://openstreetmap.org">OpenStreetMap</a> contributors').tag(
      ⦙   sync=True, o=True)
      detect_retina = Bool(False).tag(sync=True, o=True)
      no_wrap = Bool(False).tag(sync=True, o=True)
      tms = Bool(False).tag(sync=True, o=True)
      show_loading = Bool(False).tag(sync=True)
      loading = Bool(False, read_only=True).tag(sync=True)

      _load_callbacks = Instance(CallbackDispatcher, ())

From this point onwards I stopped understanding where the bug(if it is even a bug) comes from. Maybe JS implementation is not taking into account user param for max_native_zoom which makes the request wrong?

Note: Did not play with min_native_zoom, but most likely it suffers from the same problem