Fix stale tiles being shown when calling VectorTileSource#setTiles while the map is moving

[vanilla-lake]

Fix stale tiles being shown when calling VectorTileSource#setTiles while the map is moving

Before this PR, when calling VectorTileSource#setTiles, the source cache was cleared before the TileJSON was reloaded asynchronously. If the map was moving while VectorTileSource#setTiles was called, it was possible for the cache to be repopulated with the old tiles if VectorTileSource#loadTile happened to be called before the TileJSON had been reloaded. This was due to the VectorTileSource#tiles property, which is used by VectorTileSource#loadTile, only being updated asynchronously after the TileJSON had reloaded.

Launch Checklist

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.
• Write tests for all new functionality.
• Manually test the debug page.
• Add an entry inside this element for inclusion in the maplibre-gl-js changelog: <changelog></changelog>.

[github-actions]

Bundle size report:

Size Change: +5 B
Total Size Before: 194 kB
Total Size After: 194 kB

Output file	Before	After	Change
maplibre-gl.js	184 kB	184 kB	+5 B
maplibre-gl.css	9.5 kB	9.5 kB	0 B

ℹ️ View Details

Source file	Before	After	Change
rollup/build/tsc/src/source/vector_tile_source.js	1.11 kB	1.11 kB	-1 B

[HarelM]

Besides the comment above I think this looks good.
I think that someone else should go over it besides me though... @birkskyum @wipfli

[birkskyum]

Thanks! With the latest commit it lgtm.

[vanilla-lake]

No problem! 😄

[HarelM]

@vanilla-lake I'm running the benchmark and i see the following error in the console:

I have a feeling this is related to this change.
Can you please check if this is caused by this PR by any chance?
To see this do: npm run start-bench and open the browser at http://localhost:9966/bench/versions and wait for a while.

[wipfli]

I think I saw a similar error message with the headless version npm run benchmarks. Also there, you have to wait a while until this happens.

[birkskyum]

I see this sourceCaches error as well on the commit before this (c8e8345), and I see it immediately when going to the workertransfer test

[vanilla-lake]

The issue is indeed related to the changes in this PR. Sorry about that... I created PR #984 which should hopefully resolve the issue.

[khmm12]

@vanilla-lake the issue is also reproducible in "real world" if you destroy the map instance during JSON request.

UPDATE: How deep does the rabbit hole go? (c)

#1099

[vanilla-lake]

Thanks for the fix @khmm12! Your fix seems correct, since calling SourceCache.onRemove() will call VectorTileSource.onRemove() which will itself cancel _tileJSONRequest.

This error could happen anytime there is a vector tile source and Map.style becomes null or undefined. As far as I can see, the only ways this can happen is if Map.setStyle() is called with a null or undefined argument. In this case, Style._remove() should be called on the existing style from Map._updateStyle(), now cancelling any pending TileJSON requests thanks to your fix.