Fixes #899, #902: fix dask zonal.stats() bug, add dask+cupy backend, edge-case tests#911
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brendancol merged 3 commits intomasterfrom Feb 27, 2026
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The conditions `if 'mean' or 'std' or 'var' in stats_funcs` always evaluated to True because the string 'mean' is truthy. This caused compute_sum, compute_count, and compute_sum_squares to always be set, wasting work on every dask zonal.stats() call regardless of which stats were requested. Fix: use `any(s in stats_funcs for s in (...))` for correct membership testing. Add regression tests covering 7 stat subsets on both numpy and dask backends to exercise each compute flag independently.
… semantics Replaces the numpy-only, input-mutating apply() with a proper multi-backend implementation (numpy, cupy, dask+numpy, dask+cupy) that returns a new DataArray instead of mutating the input. Uses ArrayTypeFunctionMapping for dispatch and .data.dtype for validation to avoid materializing dask/cupy arrays.
Add _stats_dask_cupy() that converts dask+cupy blocks to numpy via map_blocks(x.get()) then delegates to the existing _stats_dask_numpy pipeline. Wire it into the ArrayTypeFunctionMapping dispatcher. Add five new edge-case test groups (18 test cases across backends): - all-NaN zone: documents per-backend empty-zone behavior - single-cell zones: std/var must be 0, not NaN - negative zone IDs: exercises sort-and-stride with negatives - nodata wipes zone: all finite values match nodata_values - zone in subset of blocks: zone present in only some dask chunks
brendancol
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Summary
_stats_dask_numpy()boolean short-circuit bug whereif 'mean' or 'std' or 'var' in stats_funcsalways evaluated toTrue(the string'mean'is truthy), causingcompute_sum,compute_count, andcompute_sum_squaresto be set on every call regardless of requested statsany(s in stats_funcs for s in ('mean', 'std', 'var'))for correct membership testing_stats_dask_cupy()backend (Add zonal.stats() dask+cupy backend #902): converts dask+cupy blocks to numpy viamap_blocks(x.get())then delegates to the existing_stats_dask_numpypipeline_stats_dask_cupyinto theArrayTypeFunctionMappingdispatcher (replacingnot_implemented_func)'dask+cupy'totest_default_statsandtest_zone_ids_statsparametrize lists, fix skip guards to use'cupy' in backendnodata_valuesTest plan
test_stats_subset_columns— 7 parametrized stat subsets on numpy and dask+numpytest_default_statsandtest_zone_ids_stats— now includedask+cupybackendtest_zonal.pysuite passes (106 tests)