Error occur when converting or decoding of mvt-render-test tiles

[Salkin975]

When converting MVT tiles and subsequently testing them with the decoder tests, the following errors occur:

TypeError: Cannot read properties of null (reading '0')
 - /src/vector/flat/stringFlatVector.ts:16:28

TypeError: Cannot read properties of null (reading 'length')
 - /src/vector/fsst-dictionary/stringFsstDictionaryVector.ts:102:59

RangeError: byte length of Float64Array should be a multiple of 8
 - /src/encodings/decodingUtils.ts:115:16

Error: Only delta encoding is supported for transforming length to offset streams yet.
 - /src/encodings/integerStreamDecoder.ts:308:15

Error: FastPFor is not implemented yet.
 - /src/encodings/integerDecodingUtils.ts:130:11

I am unable to determine whether this is an issue with the conversion or the decoding process.

The java decoder also seems to fail:

Decoding failed:                                                                                         
org.apache.commons.lang3.NotImplementedException: Not implemented yet.
        at org.maplibre.mlt.decoder.GeometryDecoder.decodeGeometryColumn(GeometryDecoder.java:55)
        at org.maplibre.mlt.decoder.MltDecoder.decodeMltLayer(MltDecoder.java:88)
        at org.maplibre.mlt.decoder.MltDecoder.parseBasicMVTEquivalent(MltDecoder.java:29)
        at org.maplibre.mlt.decoder.MltDecoder.decodeMlTile(MltDecoder.java:42)
        at org.maplibre.mlt.cli.Decode.main(Decode.java:73)

These are the base mvt-tiles as well as the converted mlt-tiles with wich the errors occur

FaultyTiles.zip

@TimSylvester

[TimSylvester]

Assuming you included tessellation in the encoding, the Java decoder exception is expected.

I haven't been keeping up with the state of the TypeScript decoder. It looks like some null checks are needed, but I can't tell if this is due to unsupported cases or invalid data. @HarelM?

[HarelM]

@Salkin975 keep me honest here:
The source of the faulty tiles are from the maplibre-gl-js repo render tests, converted to MVT in order to try running the render tests with MLT instead of MVT (to flush out bugs early on).
As part of this process, the above tiles failed decoding with the js version.
When we tried to decode them with the Java decoder it also failed.
So the question is if there's a bug in both Java decoder and JS decoder, or is the bug in the Java encoder.
Unfortunately, I lack the knowledge to answer this question.
@TimSylvester is there a way for you to check that the encoding is creating valid tiles?

[TimSylvester]

I think it's a bug or lack of support in the JS decoder. I will look into eliminating that Java exception.

[HarelM]

Thanks for looking into this @TimSylvester!
Please update here once the java code can decode these tiles and we'll take it up from there to solve the ts decoder when we have a java reference in our hands.

[TimSylvester]

These all decode successfully for me now. But if I enable tessellation, the geometry comparison fails, so there appears to be an encoder or decoder bug related to that.

% .../encode.jar --mvt *.mvt --outlines ALL --enable-fsst --enable-fastpfor --compare-all --verbose
Converting 14-4357-6245.mvt
Tiles match
Converting 14-8802-5374.mvt
Tiles match
Converting 4-9579-5520.mvt
Tiles match
Converting 7-70-42.mvt
Tiles match
Converting  counties-7-37-48.mvt
Tiles match

[HarelM]

Thanks for the update! Keep us posted on what you find.