Fix rx.cond literal string typing

[Alek99]

Summary

Preserve literal string unions in rx.cond overloads so expressions like rx.cond(State.condition, "green", "red") type as Var[Literal["green", "red"]] instead of widening to Var[str].

This fixes Pyright errors when passing conditional literal values to props typed as Literal[...] | Var[Literal[...]], such as Radix color_scheme.

Fixes #6538

Validation

• uv run ruff format packages/reflex-components-core/src/reflex_components_core/core/cond.py tests/units/components/core/test_cond.py
• uv run ruff check packages/reflex-components-core/src/reflex_components_core/core/cond.py tests/units/components/core/test_cond.py
• PYRIGHT_PYTHON_FORCE_VERSION=latest uv run pyright tests/units/components/core/test_cond.py packages/reflex-components-core/src/reflex_components_core/core/cond.py --pythonversion 3.14
• uv run pytest tests/units/components/core/test_cond.py

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing fix-cond-literal-typing (73af84e) with main (1224c43)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[greptile-apps]

Greptile Summary

Adds three new @overload signatures to rx.cond that use a TypeVar bound to LiteralString so expressions like rx.cond(State.flag, "green", "red") infer Var[Literal["green", "red"]] rather than widening to Var[str], eliminating Pyright errors on props typed as Literal[...] | Var[Literal[...]]. Runtime behaviour is untouched — only the type stubs change.

• Introduces LITERAL_STRING_S = TypeVar("LITERAL_STRING_S", bound=LiteralString) and three overloads covering (literal, literal), (literal, Var[U]), and (Var[T], literal) combinations.
• Updates the test fixture to explicitly separate literal_var_str (inferred Var[Literal["a"]]) from widened_var_str = cast(Var[str], …), addressing the type-annotation self-consistency issue raised in a prior review.

Confidence Score: 5/5

Safe to merge — changes are purely additive type-checker stubs with no runtime impact.

The three new overloads correctly use a LiteralString-bound TypeVar to capture literal string types without affecting the implementation body. The test updates properly distinguish Var[Literal["a"]] from Var[str] using cast, resolving the self-consistency issue flagged in a prior review. No logic paths, serialization, or runtime behaviour is altered.

No files require special attention.

Important Files Changed

Filename	Overview
packages/reflex-components-core/src/reflex_components_core/core/cond.py	Adds three new overloads using a LiteralString-bound TypeVar to preserve literal string unions through rx.cond; runtime logic is unchanged
tests/units/components/core/test_cond.py	Renames var_str to literal_var_str/widened_var_str (using cast) to distinguish Var[Literal["a"]] from Var[str] in assert_type checks, fixing the self-consistency issue flagged in a prior review
packages/reflex-components-core/news/6545.bugfix.md	Changelog entry describing the literal string type preservation fix

_{Reviews (3): Last reviewed commit: "Address review feedback on rx.cond liter..." | Re-trigger Greptile}