Add tests

crates/ruff_formatter/src/builders.rs

@@ -434,26 +434,56 @@ fn debug_assert_no_newlines(text: &str) {
     debug_assert!(!text.contains('\r'), "The content '{text}' contains an unsupported '\\r' line terminator character but text must only use line feeds '\\n' as line separator. Use '\\n' instead of '\\r' and '\\r\\n' to insert a line break in strings.");
 }
 
-/// Pushes some content to the end of the current line. Provide a reserved width in
-/// order to include the line suffix content during measurement.
+/// Pushes some content to the end of the current line.
 ///
 /// ## Examples
 ///
-/// ```
-/// use ruff_formatter::{format};
+/// ```rust
+/// use ruff_formatter::format;
 /// use ruff_formatter::prelude::*;
 ///
-/// fn main() -> FormatResult<()> {
+/// # fn main() -> FormatResult<()> {
 /// let elements = format!(SimpleFormatContext::default(), [
 ///     text("a"),
 ///     line_suffix(&text("c"), 0),
 ///     text("b")
 /// ])?;
 ///
-/// assert_eq!(
-///     "abc",
-///     elements.print()?.as_code()
-/// );
+/// assert_eq!("abc", elements.print()?.as_code());
+/// # Ok(())
+/// # }
+/// ```
+///
+/// Provide reserved width for the line suffix to include it during measurement. This
+/// will push the line suffix to the next line if it exceeds the configured line width.
+/// ```rust
+/// use ruff_formatter::{format, format_args, LineWidth, SimpleFormatContext, SimpleFormatOptions};
+/// use ruff_formatter::prelude::*;
+///
+/// # fn main() -> FormatResult<()> {
+/// let context = SimpleFormatContext::new(SimpleFormatOptions {
+///     line_width: LineWidth::try_from(2).unwrap(),
+///     ..SimpleFormatOptions::default()
+/// });
+///
+/// let elements = format!(context, [
+///     group(&format_args![
+///         &format_with(|f| {
+///             f.fill()
+///                 .entry(
+///                     &soft_line_break(),
+///                     &format_args![text("a"), text("b")],
+///                 )
+///                 .entry(
+///                     &soft_line_break(),
+///                     &line_suffix(&text("c"), 1),
+///                 )
+///                 .finish()
+///         }),
+///     ]),
+/// ])?;
+///
+/// assert_eq!("ab\nc", elements.print()?.as_code());
 /// # Ok(())
 /// # }
 /// ```

crates/ruff_formatter/src/printer/mod.rs

@@ -1731,6 +1731,36 @@ two lines`,
         assert_eq!(printed.as_code(), "[1, 2, 3]; // trailing");
     }
 
+    #[test]
+    fn line_suffix_with_reserved_width() {
+        let printed = format(&format_args![
+            group(&format_args![
+                text("["),
+                soft_block_indent(&format_with(|f| {
+                    f.fill()
+                        .entry(
+                            &soft_line_break_or_space(),
+                            &format_args!(text("1"), text(",")),
+                        )
+                        .entry(
+                            &soft_line_break_or_space(),
+                            &format_args!(text("2"), text(",")),
+                        )
+                        .entry(
+                            &soft_line_break_or_space(),
+                            &format_args!(text("3"), if_group_breaks(&text(","))),
+                        )
+                        .finish()
+                })),
+                text("]")
+            ]),
+            text(";"),
+            line_suffix(&format_args![space(), text("// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")], 80)
+        ]);
+
+        assert_eq!(printed.as_code(), "[\n  1, 2, 3\n]; // aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
+    }
+
     #[test]
     fn conditional_with_group_id_in_fits() {
         let content = format_with(|f| {