Use typing_extensions.TypeAlias for PYI026 fixes on pre-3.10

[charliermarsh]

Closes #6695.

[Skylion007]

I wonder if it would be more useful to generalize this into a generic backport import helper.

IE. something that would automatically downgrade typing.TypeAlias. Alternatively, I wonder if you could use the pyupgrade import rules logic here and always apply that rule, but only to this specific import. It would either be a NOOP or automatically fix the import if the import was moved to the typing module.

That also has the added benefit of only having to maintain the version when a new import was introduced in one place (the pyupgrade rules).

[Skylion007]

The logic could even be folded into the helper which inserts the import if you do it pyupgrade way.

[Skylion007]

Note that, in some cases, it may be preferable to continue importing members from typing_extensions even after they're added to the Python standard library, as typing_extensions can backport bugfixes and optimizations from later Python versions. This rule thus avoids flagging imports from typing_extensions in such cases.

Seems like more reason to use the helper from this rule here: https://beta.ruff.rs/docs/rules/deprecated-import/

[charliermarsh]

Nice idea, I will look into it separately. There are a few other places where this would be useful, like PYI019 which suggests typing.Self.

[charliermarsh]

Yup agreed. (I did check if that applied to TypeAlias and it does not.)

[charliermarsh]

Adding a TODO, I may look into it tonight.

[github-actions]

PR Check Results

Ecosystem

ℹ️ ecosystem check detected changes. (+0, -2, 0 error(s))

typeshed (+0, -2)

- stdlib/builtins.pyi:1666:1: PYI026 Use `typing.TypeAlias` for type alias, e.g., `_SupportsSomeKindOfPow: typing.TypeAlias = _SupportsPow2[Any, Any] | _SupportsPow3NoneOnly[Any, Any] | _SupportsPow3[Any, Any, Any]`
- stdlib/builtins.pyi:218:1: PYI026 Use `typing.TypeAlias` for type alias, e.g., `_LiteralInteger: typing.TypeAlias = _PositiveInteger | _NegativeInteger | Literal[0]`

Rules changed: 1

Rule	Changes	Additions	Removals
PYI026	2	0	2

Benchmark

Linux

group                                      main                                   pr
-----                                      ----                                   --
formatter/large/dataset.py                 1.02      3.9±0.02ms    10.4 MB/sec    1.00      3.9±0.02ms    10.5 MB/sec
formatter/numpy/ctypeslib.py               1.01    821.1±3.88µs    20.3 MB/sec    1.00    815.5±3.47µs    20.4 MB/sec
formatter/numpy/globals.py                 1.00     85.7±0.46µs    34.4 MB/sec    1.00     85.4±0.42µs    34.6 MB/sec
formatter/pydantic/types.py                1.04  1654.8±54.56µs    15.4 MB/sec    1.00  1589.8±18.72µs    16.0 MB/sec
linter/all-rules/large/dataset.py          1.00     12.2±0.04ms     3.3 MB/sec    1.02     12.5±0.39ms     3.3 MB/sec
linter/all-rules/numpy/ctypeslib.py        1.00      3.3±0.01ms     5.1 MB/sec    1.00      3.3±0.04ms     5.1 MB/sec
linter/all-rules/numpy/globals.py          1.04   484.5±27.63µs     6.1 MB/sec    1.00    465.6±1.25µs     6.3 MB/sec
linter/all-rules/pydantic/types.py         1.01      6.4±0.03ms     4.0 MB/sec    1.00      6.3±0.02ms     4.1 MB/sec
linter/default-rules/large/dataset.py      1.01      6.5±0.02ms     6.2 MB/sec    1.00      6.5±0.04ms     6.3 MB/sec
linter/default-rules/numpy/ctypeslib.py    1.01  1450.3±21.12µs    11.5 MB/sec    1.00  1433.9±13.44µs    11.6 MB/sec
linter/default-rules/numpy/globals.py      1.02    171.1±6.06µs    17.2 MB/sec    1.00    168.0±2.16µs    17.6 MB/sec
linter/default-rules/pydantic/types.py     1.01      3.0±0.01ms     8.6 MB/sec    1.00      2.9±0.04ms     8.7 MB/sec

Windows

group                                      main                                    pr
-----                                      ----                                    --
formatter/large/dataset.py                 1.00      4.7±0.21ms     8.7 MB/sec     1.00      4.7±0.24ms     8.7 MB/sec
formatter/numpy/ctypeslib.py               1.00   972.0±41.74µs    17.1 MB/sec     1.00   975.2±41.60µs    17.1 MB/sec
formatter/numpy/globals.py                 1.00     98.4±5.11µs    30.0 MB/sec     1.06   104.7±17.17µs    28.2 MB/sec
formatter/pydantic/types.py                1.01  1970.1±172.06µs    12.9 MB/sec    1.00  1959.3±123.97µs    13.0 MB/sec
linter/all-rules/large/dataset.py          1.02     16.4±0.52ms     2.5 MB/sec     1.00     16.1±0.51ms     2.5 MB/sec
linter/all-rules/numpy/ctypeslib.py        1.00      4.5±0.19ms     3.7 MB/sec     1.00      4.4±0.19ms     3.7 MB/sec
linter/all-rules/numpy/globals.py          1.00   552.5±21.74µs     5.3 MB/sec     1.04   575.6±38.97µs     5.1 MB/sec
linter/all-rules/pydantic/types.py         1.00      8.4±0.31ms     3.0 MB/sec     1.00      8.4±0.37ms     3.0 MB/sec
linter/default-rules/large/dataset.py      1.01      9.0±0.24ms     4.5 MB/sec     1.00      8.9±0.30ms     4.6 MB/sec
linter/default-rules/numpy/ctypeslib.py    1.00  1901.9±75.79µs     8.8 MB/sec     1.01  1911.8±63.80µs     8.7 MB/sec
linter/default-rules/numpy/globals.py      1.00   220.1±11.69µs    13.4 MB/sec     1.02   224.9±15.96µs    13.1 MB/sec
linter/default-rules/pydantic/types.py     1.00      4.0±0.26ms     6.3 MB/sec     1.01      4.1±0.26ms     6.2 MB/sec