FXC-3795 improving type hints for Tidy3dBaseModel

[dmarek-flex]

Testing out better type hints for these commonly used method, especially updated_copy

Greptile Overview

Updated On: 2025-10-22 14:25:57 UTC

Greptile Summary

This PR modernizes type hints in Tidy3dBaseModel by replacing explicit Tidy3dBaseModel return types with the Self type from typing_extensions. This affects 11 methods including copy(), updated_copy(), and several from_*() classmethods. The change enables type checkers to correctly infer that when a subclass (e.g., Simulation, Structure) calls these methods, they return instances of the subclass rather than the base class. This improves IDE autocomplete, catches type errors earlier, and follows modern Python typing best practices. Since Self is a pure type-checking construct available via typing_extensions, this change has zero runtime impact and maintains full backward compatibility while significantly improving the developer experience across the entire Tidy3D codebase.

Changed Files

Filename	Score	Overview
tidy3d/components/base.py	5/5	Updated return type annotations from Tidy3dBaseModel to Self for 11 methods to improve type inference for subclasses

Confidence score: 5/5

• This PR is extremely safe to merge with no risk of runtime issues or breaking changes
• Score reflects that Self is a pure type-checking construct with zero runtime behavior changes and is fully compatible with pydantic v1 via typing_extensions
• No files require special attention; this is a straightforward typing improvement that benefits the entire codebase

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Diff Coverage

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

• tidy3d/components/base.py (100%)

Summary

• Total: 7 lines
• Missing: 0 lines
• Coverage: 100%

[dmarek-flex]

@yaugenst-flex Not sure about best way to put it in the docstring. But that approach is what AI suggested

[yaugenst-flex]

Thanks @dmarek-flex this is useful! The Self in the docstrings is fine I think, it's definitely correct. We'll have to see how confusing it is in the docs.
Note that we should add typing_extensions as an explicit dependency if we require it, even though it's already available as a transient dependency.