fix(Medium2D): fix subdivision when merged geometry is a polygon with holes

[weiliangjin2021]

Greptile Overview

Greptile Summary

Fixed handling of polygons with holes (interiors) in the subdivide() function. When merged geometry results in a polygon with holes, the function now properly converts it into a PolySlab with subtraction operations using GeometryGroup. The fix also includes a refactoring of evaluate_inf_shape() to extract coordinate processing into a helper function for better code organization.

• Fixed shapely_to_polyslab() helper function in utils_2d.py:125 to handle polygons with interior holes by creating a ClipOperation with difference operation
• Refactored evaluate_inf_shape() in base.py:724 to use _processed_coords() helper for cleaner coordinate processing
• Added comprehensive test case test_subdivide_geometry_group_with_polygon_holes() that verifies the fix by checking for ClipOperation with difference operation in finalized structures
• Updated CHANGELOG.md with user-facing description of the fix

Confidence Score: 4/5

• This PR is safe to merge with minor type annotation issue
• The core logic fix is sound and properly handles polygon holes via subtraction operations. Comprehensive test coverage validates the fix. However, the return type annotation of shapely_to_polyslab() is incorrect - it declares -> PolySlab but can return ClipOperation when holes exist. This won't cause runtime issues since the outer function expects Geometry, but it creates type checking inconsistency.
• Pay close attention to tidy3d/components/geometry/utils_2d.py due to type annotation mismatch

Important Files Changed

File Analysis

Filename	Score	Overview
tidy3d/components/geometry/base.py	5/5	Refactored evaluate_inf_shape() to extract coordinate processing into helper function for better code organization
tidy3d/components/geometry/utils_2d.py	4/5	Fixed handling of polygons with holes by converting them to subtraction operations; has incorrect return type annotation
tests/test_components/test_geometry.py	5/5	Added comprehensive test for subdivide with geometry groups containing polygon holes

Sequence Diagram

sequenceDiagram
    participant Sim as Simulation
    participant Sub as subdivide()
    participant STP as shapely_to_polyslab()
    participant Geo as Geometry
    participant CO as ClipOperation
    
    Sim->>Sub: subdivide(geom, structures)
    Note over Sub: Process geometry with<br/>neighboring structures
    Sub->>Sub: Convert shapely polygons<br/>to multipolygon
    
    loop For each polygon
        Sub->>STP: shapely_to_polyslab(polygon, axis, center)
        
        alt Polygon has no holes
            STP->>Geo: Create PolySlab with exterior vertices
            Geo-->>STP: Return PolySlab
        else Polygon has holes (interiors)
            STP->>Geo: Create PolySlab with exterior vertices
            STP->>Geo: Create PolySlab for each interior
            STP->>Geo: Create GeometryGroup from interiors
            STP->>CO: polyslab - GeometryGroup
            Note over CO: Creates ClipOperation<br/>with operation="difference"
            CO-->>STP: Return ClipOperation
        end
        
        STP-->>Sub: Return Geometry (PolySlab or ClipOperation)
    end
    
    Sub-->>Sim: Return list of (Geometry, Structure, Structure)
    Note over Sim: Finalized structures contain<br/>ClipOperation with difference operation

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Diff Coverage

Diff: origin/develop...HEAD, staged and unstaged changes

• tidy3d/components/geometry/base.py (100%)
• tidy3d/components/geometry/utils_2d.py (100%)

Summary

• Total: 17 lines
• Missing: 0 lines
• Coverage: 100%

[dmarek-flex]

LGTM! 🖖