Fix datashader failing with single-category Categorical#539
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Fix datashader failing with single-category Categorical#539
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When a pd.Categorical column has only 1 category, datashader's ds.by() still produces a 3D DataArray requiring a color_key. The >1 guard was causing color_key to be None and groups to fall back to count-based aggregation, both leading to errors or incorrect output. Changes: - Change color_key guard from >1 to >0 for both shapes and points - Change groups guard from >1 to >=1 for both shapes and points - Use _hex_no_alpha in points color_key construction for consistency Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
color_vector.categories.values can contain named colors like "lightgreen", not just hex strings. Only apply _hex_no_alpha when the value starts with "#". Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
… test The test_datashader_single_group_named_color test didn't reproduce a failure on main (it only caught an intermediate regression within this PR), so remove it. Add the issue URL and detailed docstrings to the two tests that do reproduce the #483 bug on main. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The condition `groups is None or len(groups) >= 1` was always true since groups is either None or a non-empty list. Simplify to just `col_for_color is not None`, which makes the intent clearer: use categorical/reduction aggregation when there's a color column, otherwise fall back to plain count aggregation. Also note: render_labels does not use datashader, so despite the #483 issue title mentioning labels, this bug only affects shapes and points. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The color_key construction logic was duplicated between _render_shapes and _render_points. Extract into a shared helper that also caches the categories lookup and keeps the hex-vs-named-color guard in one place. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #539 +/- ##
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+ Coverage 83.83% 84.00% +0.16%
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Files 8 9 +1
Lines 2568 2600 +32
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+ Hits 2153 2184 +31
- Misses 415 416 +1
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Summary
render_labelswith DataShader fails when coloring by a pd.Categorical with only 1 category #483: datashader raisesValueErrorwhen rendering shapes/points with apd.Categoricalcolumn that has only 1 categorycolor_keyguard from> 1to> 0so a single-category Categorical still produces a valid color key for datashadergroupsguard from> 1to>= 1so a single group uses categorical aggregation instead of falling back to count-based heatmap_hex_no_alphain pointscolor_keyconstruction for consistency with the shapes pathTest plan
test_plot_datashader_single_categoryfor shapestest_plot_datashader_single_category_pointsfor pointsmain)🤖 Generated with Claude Code