Improve with statement comment handling and expression breaking (#6621)

## Summary

The motivating code here was:

```python
with test as (
    # test
foo):
    pass
```

Which we were formatting as:

```python
with test as
# test
(foo):
    pass
```

`with` statements are oddly difficult. This PR makes a bunch of subtle
modifications and adds a more extensive test suite. For example, we now
only preserve parentheses if there's more than one `WithItem` _or_ a
trailing comma; before, we always preserved.

Our formatting is_not_ the same as Black, but here's a diff of our
formatted code vs. Black's for the `with.py` test suite. The primary
difference is that we tend to break parentheses when they contain
comments rather than move them to the end of the life (this is a
consistent difference that we make across the codebase):

```diff
diff --git a/crates/ruff_python_formatter/foo.py b/crates/ruff_python_formatter/foo.py
index 85e761080..31625c876 100644
--- a/crates/ruff_python_formatter/foo.py
+++ b/crates/ruff_python_formatter/foo.py
@@ -1,6 +1,4 @@
-with (
-    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
-), aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa:
+with aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa, aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa:
     ...
     # trailing
 
@@ -16,28 +14,33 @@ with (
     # trailing
 
 
-with a, b:  # a  # comma  # c  # colon
+with (
+    a,  # a  # comma
+    b,  # c
+):  # colon
     ...
 
 
 with (
-    a as  # a  # as
-    # own line
-    b,  # b  # comma
+    a as (  # a  # as
+        # own line
+        b
+    ),  # b  # comma
     c,  # c
 ):  # colon
     ...  # body
     # body trailing own
 
-with (
-    a as  # a  # as
+with a as (  # a  # as
     # own line
-    bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb  # b
-):
+    bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+):  # b
     pass
 
 
-with (a,):  # magic trailing comma
+with (
+    a,
+):  # magic trailing comma
     ...
 
 
@@ -47,6 +50,7 @@ with a:  # should remove brackets
 with aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb as c:
     ...
 
+
 with (
     # leading comment
     a
@@ -74,8 +78,7 @@ with (
 with (
     a  # trailing same line comment
     # trailing own line comment
-    as b
-):
+) as b:
     ...
 
 with (
@@ -87,7 +90,9 @@ with (
 with (
     a
     # trailing own line comment
-) as b:  # trailing as same line comment  # trailing b same line comment
+) as (  # trailing as same line comment
+    b
+):  # trailing b same line comment
     ...
 
 with (
@@ -124,18 +129,24 @@ with (  # comment
     ...
 
 with (  # outer comment
-    CtxManager1() as example1,  # inner comment
+    (  # inner comment
+        CtxManager1()
+    ) as example1,
     CtxManager2() as example2,
     CtxManager3() as example3,
 ):
     ...
 
-with CtxManager() as example:  # outer comment
+with (  # outer comment
+    CtxManager()
+) as example:
     ...
 
 with (  # outer comment
     CtxManager()
-) as example, CtxManager2() as example2:  # inner comment
+) as example, (  # inner comment
+    CtxManager2()
+) as example2:
     ...
 
 with (  # outer comment
@@ -145,7 +156,9 @@ with (  # outer comment
     ...
 
 with (  # outer comment
-    (CtxManager1()),  # inner comment
+    (  # inner comment
+        CtxManager1()
+    ),
     CtxManager2(),
 ) as example:
     ...
@@ -179,7 +192,9 @@ with (
 ):
     pass
 
-with a as (b):  # foo
+with a as (  # foo
+    b
+):
     pass
 
 with f(
@@ -209,17 +224,13 @@ with f(
 ) as b, c as d:
     pass
 
-with (
-    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
-) as b:
+with aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb as b:
     pass
 
 with aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb as b:
     pass
 
-with (
-    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
-) as b, c as d:
+with aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb as b, c as d:
     pass
 
 with (
@@ -230,6 +241,8 @@ with (
     pass
 
 with (
-    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
-) as b, c as d:
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb as b,
+    c as d,
+):
     pass
```

Closes https://github.com/astral-sh/ruff/issues/6600.
## Test Plan

Before:

| project      | similarity index |
|--------------|------------------|
| cpython      | 0.75473          |
| django       | 0.99804          |
| transformers | 0.99618          |
| twine        | 0.99876          |
| typeshed     | 0.74292          |
| warehouse    | 0.99601          |
| zulip        | 0.99727          |

After:

| project      | similarity index |
|--------------|------------------|
| cpython      | 0.75473          |
| django       | 0.99804          |
| transformers | 0.99618          |
| twine        | 0.99876          |
| typeshed     | 0.74292          |
| warehouse    | 0.99601          |
| zulip        | 0.99727          |

`cargo test`

crates/ruff_python_formatter/src/other/commas.rs

@@ -0,0 +1,31 @@
+use ruff_python_trivia::{SimpleToken, SimpleTokenKind, SimpleTokenizer};
+use ruff_text_size::TextRange;
+
+use crate::prelude::*;
+use crate::{MagicTrailingComma, PyFormatOptions};
+
+/// Returns `true` if the range ends with a magic trailing comma (and the magic trailing comma
+/// should be respected).
+pub(crate) fn has_magic_trailing_comma(
+    range: TextRange,
+    options: &PyFormatOptions,
+    context: &PyFormatContext,
+) -> bool {
+    match options.magic_trailing_comma() {
+        MagicTrailingComma::Respect => {
+            let first_token = SimpleTokenizer::new(context.source(), range)
+                .skip_trivia()
+                // Skip over any closing parentheses belonging to the expression
+                .find(|token| token.kind() != SimpleTokenKind::RParen);
+
+            matches!(
+                first_token,
+                Some(SimpleToken {
+                    kind: SimpleTokenKind::Comma,
+                    ..
+                })
+            )
+        }
+        MagicTrailingComma::Ignore => false,
+    }
+}

crates/ruff_python_formatter/src/other/mod.rs

@@ -1,5 +1,6 @@
 pub(crate) mod alias;
 pub(crate) mod arguments;
+pub(crate) mod commas;
 pub(crate) mod comprehension;
 pub(crate) mod decorator;
 pub(crate) mod elif_else_clause;

crates/ruff_python_formatter/src/other/with_item.rs

@@ -1,10 +1,9 @@
+use ruff_formatter::{write, Buffer, FormatResult};
 use ruff_python_ast::WithItem;
 
-use ruff_formatter::{write, Buffer, FormatResult};
-
-use crate::comments::{leading_comments, trailing_comments, SourceComment};
+use crate::comments::SourceComment;
 use crate::expression::maybe_parenthesize_expression;
-use crate::expression::parentheses::Parenthesize;
+use crate::expression::parentheses::{parenthesized, Parentheses, Parenthesize};
 use crate::prelude::*;
 use crate::{FormatNodeRule, PyFormatter};
 
@@ -22,28 +21,33 @@ impl FormatNodeRule<WithItem> for FormatWithItem {
         let comments = f.context().comments().clone();
         let trailing_as_comments = comments.dangling_comments(item);
 
-        maybe_parenthesize_expression(context_expr, item, Parenthesize::IfRequired).fmt(f)?;
+        write!(
+            f,
+            [maybe_parenthesize_expression(
+                context_expr,
+                item,
+                Parenthesize::IfRequired
+            )]
+        )?;
 
         if let Some(optional_vars) = optional_vars {
-            write!(
-                f,
-                [space(), text("as"), trailing_comments(trailing_as_comments)]
-            )?;
-            let leading_var_comments = comments.leading_comments(optional_vars.as_ref());
-            if leading_var_comments.is_empty() {
-                write!(f, [space(), optional_vars.format()])?;
+            write!(f, [space(), text("as"), space()])?;
+
+            if trailing_as_comments.is_empty() {
+                write!(f, [optional_vars.format()])?;
             } else {
                 write!(
                     f,
-                    [
-                        // Otherwise the comment would end up on the same line as the `as`
-                        hard_line_break(),
-                        leading_comments(leading_var_comments),
-                        optional_vars.format()
-                    ]
+                    [parenthesized(
+                        "(",
+                        &optional_vars.format().with_options(Parentheses::Never),
+                        ")",
+                    )
+                    .with_dangling_comments(trailing_as_comments)]
                 )?;
             }
         }
+
         Ok(())
     }