Format named expressions (walrus operator)

[konstin]

Summary

Format named expressions (walrus operator) such a value := f().

Unlike tuples, named expression parentheses are not part of the range even when mandatory, so mapping optional parentheses to always gives us decent formatting without implementing all PEP 572 rules on when we need parentheses where other expressions wouldn't. We might want to revisit this decision later and implement special cases, but for now this gives us what we need.

Test Plan

black fixtures, i added some fixtures and checked django and cpython for stability.

Closes #5613

[MichaReiser]

Hmm, this shouldn't be necessary at all. Let me check our test setup. It should automatically delete fixed snapshots

[github-actions]

PR Check Results

Ecosystem

✅ ecosystem check detected no changes.

Benchmark

Linux

group                                      main                                   pr
-----                                      ----                                   --
formatter/large/dataset.py                 1.00      8.5±0.01ms     4.8 MB/sec    1.00      8.5±0.02ms     4.8 MB/sec
formatter/numpy/ctypeslib.py               1.00   1799.7±4.08µs     9.3 MB/sec    1.01   1810.7±3.80µs     9.2 MB/sec
formatter/numpy/globals.py                 1.00    198.5±1.17µs    14.9 MB/sec    1.01    199.7±1.68µs    14.8 MB/sec
formatter/pydantic/types.py                1.00      4.1±0.01ms     6.2 MB/sec    1.00      4.1±0.01ms     6.3 MB/sec
linter/all-rules/large/dataset.py          1.00     14.1±0.03ms     2.9 MB/sec    1.00     14.1±0.04ms     2.9 MB/sec
linter/all-rules/numpy/ctypeslib.py        1.00      3.5±0.00ms     4.7 MB/sec    1.00      3.5±0.00ms     4.7 MB/sec
linter/all-rules/numpy/globals.py          1.00    363.9±1.37µs     8.1 MB/sec    1.00    362.7±0.79µs     8.1 MB/sec
linter/all-rules/pydantic/types.py         1.00      6.2±0.02ms     4.1 MB/sec    1.01      6.3±0.05ms     4.1 MB/sec
linter/default-rules/large/dataset.py      1.00      7.2±0.01ms     5.6 MB/sec    1.00      7.2±0.01ms     5.7 MB/sec
linter/default-rules/numpy/ctypeslib.py    1.00  1480.9±11.19µs    11.2 MB/sec    1.00   1473.6±1.92µs    11.3 MB/sec
linter/default-rules/numpy/globals.py      1.00    157.0±0.39µs    18.8 MB/sec    1.00    156.3±0.20µs    18.9 MB/sec
linter/default-rules/pydantic/types.py     1.01      3.2±0.01ms     7.9 MB/sec    1.00      3.2±0.01ms     8.0 MB/sec

Windows

group                                      main                                   pr
-----                                      ----                                   --
formatter/large/dataset.py                 1.00     12.3±0.61ms     3.3 MB/sec    1.06     13.1±0.39ms     3.1 MB/sec
formatter/numpy/ctypeslib.py               1.00      2.6±0.10ms     6.4 MB/sec    1.11      2.9±0.13ms     5.7 MB/sec
formatter/numpy/globals.py                 1.00   305.1±23.08µs     9.7 MB/sec    1.06   324.7±23.77µs     9.1 MB/sec
formatter/pydantic/types.py                1.00      5.6±0.23ms     4.5 MB/sec    1.14      6.4±0.22ms     4.0 MB/sec
linter/all-rules/large/dataset.py          1.00     20.8±0.81ms  2006.2 KB/sec    1.02     21.2±0.48ms  1962.5 KB/sec
linter/all-rules/numpy/ctypeslib.py        1.00      5.2±0.20ms     3.2 MB/sec    1.04      5.4±0.17ms     3.1 MB/sec
linter/all-rules/numpy/globals.py          1.00   625.7±35.54µs     4.7 MB/sec    1.06   660.3±23.72µs     4.5 MB/sec
linter/all-rules/pydantic/types.py         1.00      8.9±0.29ms     2.9 MB/sec    1.08      9.6±0.36ms     2.6 MB/sec
linter/default-rules/large/dataset.py      1.00     10.5±0.30ms     3.9 MB/sec    1.11     11.7±0.36ms     3.5 MB/sec
linter/default-rules/numpy/ctypeslib.py    1.00      2.2±0.09ms     7.4 MB/sec    1.11      2.5±0.09ms     6.7 MB/sec
linter/default-rules/numpy/globals.py      1.00   258.0±12.35µs    11.4 MB/sec    1.10   283.9±10.65µs    10.4 MB/sec
linter/default-rules/pydantic/types.py     1.00      4.9±0.27ms     5.2 MB/sec    1.06      5.2±0.21ms     4.9 MB/sec