format StmtWith (#5350)

crates/ruff_python_formatter/src/other/with_item.rs

@@ -1,4 +1,6 @@
-use crate::{not_yet_implemented, FormatNodeRule, PyFormatter};
+use crate::expression::parentheses::Parenthesize;
+use crate::prelude::*;
+use crate::{FormatNodeRule, PyFormatter};
 use ruff_formatter::{write, Buffer, FormatResult};
 use rustpython_parser::ast::WithItem;
 
@@ -7,6 +9,22 @@ pub struct FormatWithItem;
 
 impl FormatNodeRule<WithItem> for FormatWithItem {
     fn fmt_fields(&self, item: &WithItem, f: &mut PyFormatter) -> FormatResult<()> {
-        write!(f, [not_yet_implemented(item)])
+        let WithItem {
+            range: _,
+            context_expr,
+            optional_vars,
+        } = item;
+
+        let inner = format_with(|f| {
+            write!(
+                f,
+                [context_expr.format().with_options(Parenthesize::IfBreaks)]
+            )?;
+            if let Some(optional_vars) = optional_vars {
+                write!(f, [space(), text("as"), space(), optional_vars.format()])?;
+            }
+            Ok(())
+        });
+        write!(f, [group(&inner)])
     }
 }