ruff/crates
Brent Westbrook 0bec5c0362
Fix comment placement in lambda parameters (#21868)
Summary
--

This PR makes two changes to comment placement in lambda parameters.
First, we
now insert a line break if the first parameter has a leading comment:

```py
# input
(
    lambda
    * # comment 2
    x:
    x
)

# main
(
    lambda # comment 2
    *x: x
)

# this PR
(
    lambda
	# comment 2
    *x: x
)
```

Note the missing space in the output from main. This case is currently
unstable
on main. Also note that the new formatting is more consistent with our
stable
formatting in cases where the lambda has its own dangling comment:

```py
# input
(
    lambda # comment 1
    * # comment 2
    x:
    x
)

# output
(
    lambda  # comment 1
    # comment 2
    *x: x
)
```

and when a parameter without a comment precedes the split `*x`:

```py
# input
(
    lambda y,
    * # comment 2
    x:
    x
)

# output
(
    lambda y,
    # comment 2
    *x: x
)
```

This does change the stable formatting, but I think such cases are rare
(expecting zero hits in the ecosystem report), this fixes an existing
instability, and it should not change any code we've previously
formatted.

Second, this PR modifies the comment placement such that `# comment 2`
in these
outputs is still a leading comment on the parameter. This is also not
the case
on main, where it becomes a [dangling lambda
comment](https://play.ruff.rs/3b29bb7e-70e4-4365-88e0-e60fe1857a35?secondary=Comments).
This doesn't cause any
instability that I'm aware of on main, but it does cause problems when
trying to
adjust the placement of dangling lambda comments in #21385. Changing the
placement in this way should not affect any formatting here.

Test Plan
--

New lambda tests, plus existing tests covering the cases above with
multiple
comments around the parameters (see lambda.py 122-143, and 122-205 or so
more
broadly)

I also checked manually that the comments are now leading on the
parameter:

```shell
❯ cargo run --bin ruff_python_formatter -- --emit stdout --target-version 3.10 --print-comments <<EOF
(
    lambda
        # comment 2
    *x: x
)
EOF
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.15s
     Running `target/debug/ruff_python_formatter --emit stdout --target-version 3.10 --print-comments`
# Comment decoration: Range, Preceding, Following, Enclosing, Comment
21..32, None, Some((Parameters, 37..39)), (ExprLambda, 6..42), "# comment 2"
{
    Node {
        kind: Parameter,
        range: 37..39,
        source: `*x`,
    }: {
        "leading": [
            SourceComment {
                text: "# comment 2",
                position: OwnLine,
                formatted: true,
            },
        ],
        "dangling": [],
        "trailing": [],
    },
}
(
    lambda
    # comment 2
    *x: x
)
```

But I didn't see a great place to put a test like this. Is there
somewhere I can assert this comment placement since it doesn't affect
any formatting yet? Or is it okay to wait until we use this in #21385?
2025-12-09 14:07:48 -05:00
..
ruff apply range suppressions to filter diagnostics (#21623) 2025-12-08 16:11:59 -08:00
ruff_annotate_snippets Only render hyperlinks for terminals known to support them (#21519) 2025-11-19 10:02:58 +01:00
ruff_benchmark Move `Token`, `TokenKind` and `Tokens` to `ruff-python-ast` (#21760) 2025-12-02 20:10:46 +01:00
ruff_cache Switch to Rust 2024 edition (#18129) 2025-05-16 13:25:28 +02:00
ruff_db [ty] Remove legacy `concise_message` fallback behavior (#21847) 2025-12-08 16:19:01 +00:00
ruff_dev Update Rust toolchain to 1.91 (#21179) 2025-11-01 01:50:58 +00:00
ruff_diagnostics [ty] Add code action to ignore diagnostic on the current line (#21595) 2025-11-29 15:41:54 +01:00
ruff_formatter [ty] Use "cannot" consistently over "can not" (#21255) 2025-11-03 10:38:20 -05:00
ruff_graph [ty] Teach `ty` the meaning of desperation (try ancestor `pyproject.toml`s as search-paths if module resolution fails) (#21745) 2025-12-03 15:04:36 -05:00
ruff_index Update Rust toolchain to 1.88 and MSRV to 1.86 (#19011) 2025-06-28 20:24:00 +02:00
ruff_linter [`pylint`] Detect subclasses of builtin exceptions (`PLW0133`) (#21382) 2025-12-09 13:49:55 -05:00
ruff_macros Document when a rule was added (#21035) 2025-10-23 14:48:41 -04:00
ruff_memory_usage [ty] Enable LRU collection for parsed module (#21749) 2025-12-03 12:16:18 +01:00
ruff_notebook [ty] Respect notebook cell boundaries when adding an auto import (#21322) 2025-11-13 18:58:08 +01:00
ruff_options_metadata Update Rust toolchain to 1.89 (#19807) 2025-08-07 18:21:50 +02:00
ruff_python_ast Include more details in Tokens 'offset is inside token' panic message (#21860) 2025-12-09 11:12:35 +01:00
ruff_python_ast_integration_tests Add token based `parenthesized_ranges` implementation (#21738) 2025-12-03 08:15:17 +00:00
ruff_python_codegen Move `Token`, `TokenKind` and `Tokens` to `ruff-python-ast` (#21760) 2025-12-02 20:10:46 +01:00
ruff_python_formatter Fix comment placement in lambda parameters (#21868) 2025-12-09 14:07:48 -05:00
ruff_python_importer Move `Token`, `TokenKind` and `Tokens` to `ruff-python-ast` (#21760) 2025-12-02 20:10:46 +01:00
ruff_python_index Move `Token`, `TokenKind` and `Tokens` to `ruff-python-ast` (#21760) 2025-12-02 20:10:46 +01:00
ruff_python_literal Switch to Rust 2024 edition (#18129) 2025-05-16 13:25:28 +02:00
ruff_python_parser [`flake8-bugbear`] Catch `yield` expressions within other statements (`B901`) (#21200) 2025-12-03 12:05:15 -05:00
ruff_python_semantic Add rule to detect unnecessary class properties (#21535) 2025-11-26 09:31:22 +01:00
ruff_python_stdlib [`flake8-bugbear`] Accept immutable slice default arguments (`B008`) (#21823) 2025-12-08 14:00:43 -05:00
ruff_python_trivia Handle t-string prefixes in `SimpleTokenizer` (#20578) 2025-09-25 14:33:37 -05:00
ruff_python_trivia_integration_tests Handle t-string prefixes in `SimpleTokenizer` (#20578) 2025-09-25 14:33:37 -05:00
ruff_server apply range suppressions to filter diagnostics (#21623) 2025-12-08 16:11:59 -08:00
ruff_source_file Use `memchr` for computing line indexes (#21838) 2025-12-08 08:50:51 -05:00
ruff_text_size [ty] Fix subtraction overflow bug 2025-11-21 15:07:37 -05:00
ruff_wasm apply range suppressions to filter diagnostics (#21623) 2025-12-08 16:11:59 -08:00
ruff_workspace `analyze`: Add option to skip over imports in `TYPE_CHECKING` blocks (#21472) 2025-11-16 12:30:24 +00:00
ty [ty] Make Python-version subdiagnostics less verbose (#21849) 2025-12-08 15:58:23 +00:00
ty_combine [ty] Disallow std::env and io methods in most ty crates (#20046) 2025-08-22 11:13:47 -07:00
ty_completion_eval [ty] Update completion eval to include modules 2025-12-04 17:37:37 -05:00
ty_ide [ty] Use default settings in completion tests 2025-12-09 10:42:46 -05:00
ty_project [ty] Enable LRU collection for parsed module (#21749) 2025-12-03 12:16:18 +01:00
ty_python_semantic Fix stack overflow with recursive generic protocols (depth limit) (#21858) 2025-12-09 09:05:18 -08:00
ty_server [ty] Stabilize auto-import 2025-12-09 09:40:38 -05:00
ty_static [ty] improve base conda distinction from child conda (#20675) 2025-10-03 13:56:06 +00:00
ty_test [ty] Remove legacy `concise_message` fallback behavior (#21847) 2025-12-08 16:19:01 +00:00
ty_vendored [ty] Carry generic context through when converting class into `Callable` (#21798) 2025-12-05 08:57:21 -05:00
ty_wasm [ty] Add code action to ignore diagnostic on the current line (#21595) 2025-11-29 15:41:54 +01:00