[6.1.0rc2] With a GeoJSON of type "MultiPolygon", the chart "Deck.gl Polygon" shows only the first geometry

[herve-lg]

Bug description

For your information, this bug https://github.com/apache/superset/issues/38660#issuecomment-4064750312 is still present in version 6.1.0rc2.

Screenshots/recordings

No response

Superset version

master / latest-dev

Python version

3.11

Node version

18 or greater

Browser

Chrome

Additional context

No response

Checklist

• I have searched Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

[dosubot]

Hi @herve-lg! I'm Dosu and I’m helping the superset team.

This is a confirmed, still-open bug. The root cause is in getPointsFromPolygon.ts — the function only extracts coordinates[0] from the geometry, so for MultiPolygon types, only the first polygon (e.g., Corsica for France) gets rendered. The type definitions also explicitly only support 'Polygon', not 'MultiPolygon' [1].

PR #38595 (merged March 2026) improved nested GeoJSON parsing but did not address MultiPolygon support, so this persists in 6.1.0rc2. The issue is also tracked in #32127, where a maintainer acknowledged plans to fix it as part of a deck.gl chart refactor, though no timeline has been set [2].

Workarounds in the meantime:

• Use the Deck.gl GeoJSON chart — it renders all MultiPolygon geometries correctly, though it lacks metric-based fill for choropleth visualization
• Split MultiPolygons into separate Polygon rows — works but causes data duplication and metric calculation issues

To reply, just mention @dosu.

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