fastapi - 💡(How to fix) Fix Ensure pydantic_extra_types Color encoder path is covered in tests

Describe the bug

The new jsonable_encoder() coverage for pydantic_extra_types.color.Color can be skipped in the default test environment, so the modern color-type branch added in fastapi/encoders.py may not be exercised by normal test runs.

On current master (ecace74), this command passes one color case and skips the pydantic_extra_types.color case because pydantic_extra_types is not installed in the default test environment:

$ uv run pytest tests/test_jsonable_encoder.py::test_encode_color -q -rs
.s                                                                       [100%]
=========================== short test summary info ===========================
SKIPPED [1] tests\test_jsonable_encoder.py:328: pydantic_extra_types.color not available
1 passed, 1 skipped in 0.44s

To Reproduce

1. Check out current master.
2. Run:

uv run pytest tests/test_jsonable_encoder.py::test_encode_color -q -rs

Expected behavior

The newly added pydantic_extra_types.color.Color encoder path should be covered in at least one required CI/test environment, or the optional-extra coverage should live in an explicit extra-specific test job.

Suggested solution

One of these would make the coverage explicit:

• Add pydantic-extra-types >=2.0.0 to the tests dependency group, or
• Add an extra-specific CI/test job that installs fastapi[standard] or fastapi[all] and requires the pydantic_extra_types.color branch to run.

Environment

• FastAPI commit: ecace74
• Python via uv run: CPython 3.11.15 on Windows
• Test command: uv run pytest tests/test_jsonable_encoder.py::test_encode_color -q -rs

Additional context

This is a low-severity coverage issue, not a runtime import failure. The runtime code intentionally treats pydantic_extra_types as optional.