Nothing rendering with `_getVectorTilePromise` custom implementation

[slutske22]

Nothing rendering with `_getVectorTilePromise` custom implementation

[IvanSanchez]

The code expects that promise to resolve to a vector tile, and not to the geojsonvt instance (which holds multiple tiles, at least in the general case). Leverage .getTile() on the geojsonvt instance.

[slutske22]

@IvanSanchez sorry to bother on what is more of a question than an issue, but I don't see how this is supposed to work exactly. I try something like

return vt.getTile(z, y, x) // where z, y, x comes from the coord argument

I get the error Cannot read properties of null (reading 'layers'). I dug into some of the source code and examples, and I see that _getVectorTilePromise is sometimes written to return an object with a .layers and .coords property. So I tried this:

return { layers: vt.getTile(z, x, y), coords }

But that gives the error Cannot read properties of undefined (reading 'length'). That appears to be erroring on the .features property from within the vectorgrid source code. When I check the GeoJSON being fed to geojsonvt, it seems to be a correct .features array:

Apparently sometimes the getTile function returns null. I fixed that with a check:

// With check to make sure function returns a non-null value
 return (
      vt.getTile(z, x, y)?.features ?? {
        features: [],
        numFeatures: 0,
        numPoints: 0,
        numSimplified: 0,
        source: [],
        transformed: true,
        ...coords
      }
    );

Which supresses the errors. But still, nothing renders here.

What am I doing wrong in this case? (Sandbox is updated to show the new code)

[IvanSanchez]

Read https://github.com/Leaflet/Leaflet.VectorGrid/blob/master/src/slicerWebWorker.js (or an old workerless version of the Slicer). Debug and compare how the slicer works versus how your code works.