Return dimension-appropriate empty geometries from overlay operations#696
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peterstace merged 1 commit intomasterfrom Feb 12, 2026
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Change `GeometryCollection.Dimension()` to return -1 for empty geometry collections (previously 0), distinguishing them from empty Points. This is consistent with GEOS. Update overlay operations (Union, Intersection, Difference, SymmetricDifference) to return empty geometries matching the expected result dimension (e.g. POLYGON EMPTY instead of GEOMETRYCOLLECTION EMPTY).
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Description
Change
GeometryCollection.Dimension()to return -1 for empty geometry collections (previously 0), distinguishing them from empty Points. This is consistent with GEOS.Update overlay operations (Union, Intersection, Difference, SymmetricDifference) to return empty geometries matching the expected result dimension (e.g. POLYGON EMPTY instead of GEOMETRYCOLLECTION EMPTY).
Check List
Have you:
Added unit tests? Yes.
Add cmprefimpl tests? (if appropriate?) N/A
Updated release notes? (if appropriate?) Yes.
Updated the README.md (if new functionality is added?) N/A
Fixes