ruff_python_formatter: add docstring-code-line-width internal setting (#9055)

## Summary

This does the light plumbing necessary to add a new internal option that
permits setting the line width of code examples in docstrings. The plan
is to add the corresponding user facing knob in #8854.

Note that this effectively removes the `same-as-global` configuration
style discussed [in this
comment](#8855 (comment)).
It replaces it with the `{integer}` configuration style only.

There are a lot of commits here, but they are each tiny to make review
easier because of the changes to snapshots.

## Test Plan

I added a new docstring test configuration that sets
`docstring-code-line-width = 60` and examined the differences.

Author: BurntSushi

crates/ruff_python_formatter/resources/test/fixtures/ruff/docstring_code_examples.options.json

@@ -38,5 +38,11 @@
     "docstring_code": "enabled",
     "indent_style": "tab",
     "indent_width": 4
+  },
+  {
+    "docstring_code": "enabled",
+    "docstring_code_line_width": 60,
+    "indent_style": "space",
+    "indent_width": 4
   }
 ]

crates/ruff_python_formatter/src/expression/string/docstring.rs

@@ -464,6 +464,7 @@ impl<'ast, 'buf, 'fmt, 'src> DocstringLinePrinter<'ast, 'buf, 'fmt, 'src> {
             .f
             .options()
             .clone()
+            .with_line_width(self.f.options().docstring_code_line_width())
             // It's perhaps a little odd to be hard-coding the indent
             // style here, but I believe it is necessary as a result
             // of the whitespace normalization otherwise done in

crates/ruff_python_formatter/src/options.rs

@@ -49,6 +49,12 @@ pub struct PyFormatOptions {
     /// enabled by default (opt-out) in the future.
     docstring_code: DocstringCode,
 
+    /// The preferred line width at which the formatter should wrap lines in
+    /// docstring code examples. This only has an impact when `docstring_code`
+    /// is enabled.
+    #[cfg_attr(feature = "serde", serde(default = "default_line_width"))]
+    docstring_code_line_width: LineWidth,
+
     /// Whether preview style formatting is enabled or not
     preview: PreviewMode,
 }
@@ -77,6 +83,7 @@ impl Default for PyFormatOptions {
             magic_trailing_comma: MagicTrailingComma::default(),
             source_map_generation: SourceMapGeneration::default(),
             docstring_code: DocstringCode::default(),
+            docstring_code_line_width: default_line_width(),
             preview: PreviewMode::default(),
         }
     }
@@ -119,6 +126,10 @@ impl PyFormatOptions {
         self.docstring_code
     }
 
+    pub fn docstring_code_line_width(&self) -> LineWidth {
+        self.docstring_code_line_width
+    }
+
     pub const fn preview(&self) -> PreviewMode {
         self.preview
     }

crates/ruff_python_formatter/tests/fixtures.rs

@@ -347,21 +347,23 @@ impl fmt::Display for DisplayPyOptions<'_> {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         writeln!(
             f,
-            r#"indent-style            = {indent_style}
-line-width              = {line_width}
-indent-width            = {indent_width}
-quote-style             = {quote_style:?}
-line-ending             = {line_ending:?}
-magic-trailing-comma    = {magic_trailing_comma:?}
-docstring-code          = {docstring_code:?}
-preview                 = {preview:?}"#,
+            r#"indent-style               = {indent_style}
+line-width                 = {line_width}
+indent-width               = {indent_width}
+quote-style                = {quote_style:?}
+line-ending                = {line_ending:?}
+magic-trailing-comma       = {magic_trailing_comma:?}
+docstring-code             = {docstring_code:?}
+docstring-code-line-width  = {docstring_code_line_width:?}
+preview                    = {preview:?}"#,
             indent_style = self.0.indent_style(),
             indent_width = self.0.indent_width().value(),
             line_width = self.0.line_width().value(),
             quote_style = self.0.quote_style(),
             line_ending = self.0.line_ending(),
             magic_trailing_comma = self.0.magic_trailing_comma(),
             docstring_code = self.0.docstring_code(),
+            docstring_code_line_width = self.0.docstring_code_line_width().value(),
             preview = self.0.preview()
         )
     }

crates/ruff_python_formatter/tests/snapshots/format@docstring.py.snap

@@ -166,14 +166,15 @@ def single_quoted():
 ## Outputs
 ### Output 1
 ```
-indent-style            = space
-line-width              = 88
-indent-width            = 4
-quote-style             = Double
-line-ending             = LineFeed
-magic-trailing-comma    = Respect
-docstring-code          = Disabled
-preview                 = Disabled
+indent-style               = space
+line-width                 = 88
+indent-width               = 4
+quote-style                = Double
+line-ending                = LineFeed
+magic-trailing-comma       = Respect
+docstring-code             = Disabled
+docstring-code-line-width  = 88
+preview                    = Disabled
 ```
 
 ```python
@@ -339,14 +340,15 @@ def single_quoted():
 
 ### Output 2
 ```
-indent-style            = space
-line-width              = 88
-indent-width            = 2
-quote-style             = Double
-line-ending             = LineFeed
-magic-trailing-comma    = Respect
-docstring-code          = Disabled
-preview                 = Disabled
+indent-style               = space
+line-width                 = 88
+indent-width               = 2
+quote-style                = Double
+line-ending                = LineFeed
+magic-trailing-comma       = Respect
+docstring-code             = Disabled
+docstring-code-line-width  = 88
+preview                    = Disabled
 ```
 
 ```python
@@ -512,14 +514,15 @@ def single_quoted():
 
 ### Output 3
 ```
-indent-style            = tab
-line-width              = 88
-indent-width            = 8
-quote-style             = Double
-line-ending             = LineFeed
-magic-trailing-comma    = Respect
-docstring-code          = Disabled
-preview                 = Disabled
+indent-style               = tab
+line-width                 = 88
+indent-width               = 8
+quote-style                = Double
+line-ending                = LineFeed
+magic-trailing-comma       = Respect
+docstring-code             = Disabled
+docstring-code-line-width  = 88
+preview                    = Disabled
 ```
 
 ```python
@@ -685,14 +688,15 @@ def single_quoted():
 
 ### Output 4
 ```
-indent-style            = tab
-line-width              = 88
-indent-width            = 4
-quote-style             = Double
-line-ending             = LineFeed
-magic-trailing-comma    = Respect
-docstring-code          = Disabled
-preview                 = Disabled
+indent-style               = tab
+line-width                 = 88
+indent-width               = 4
+quote-style                = Double
+line-ending                = LineFeed
+magic-trailing-comma       = Respect
+docstring-code             = Disabled
+docstring-code-line-width  = 88
+preview                    = Disabled
 ```
 
 ```python
@@ -858,14 +862,15 @@ def single_quoted():
 
 ### Output 5
 ```
-indent-style            = space
-line-width              = 88
-indent-width            = 4
-quote-style             = Single
-line-ending             = LineFeed
-magic-trailing-comma    = Respect
-docstring-code          = Disabled
-preview                 = Disabled
+indent-style               = space
+line-width                 = 88
+indent-width               = 4
+quote-style                = Single
+line-ending                = LineFeed
+magic-trailing-comma       = Respect
+docstring-code             = Disabled
+docstring-code-line-width  = 88
+preview                    = Disabled
 ```
 
 ```python