feature(formatter): Add LineSuffixBoundary IR element

crates/rome_formatter/src/format_element.rs

@@ -241,6 +241,29 @@ pub fn line_suffix(element: impl Into<FormatElement>) -> FormatElement {
     FormatElement::LineSuffix(Box::new(element.into()))
 }
 
+/// Inserts a boundary for line suffixes that forces to print all pending line suffixes. Helpful
+/// if a line sufix shouldn't pass a certain point.
+///
+/// ## Examples
+///
+/// Forces the line suffix "c" to be printed before the token `d`.
+/// ```
+/// use rome_formatter::Formatted;
+/// use rome_formatter::prelude::*;
+///
+/// let elements = format_elements![token("a"), line_suffix(token("c")), token("b"), line_suffix_boundary(), token("d")];
+///
+/// assert_eq!(
+///     "abc\nd",
+///     Formatted::new(elements, PrinterOptions::default())
+///         .print()
+///         .as_code()
+/// );
+/// ```
+pub const fn line_suffix_boundary() -> FormatElement {
+    FormatElement::LineSuffixBoundary
+}
+
 /// Mark a [FormatElement] as being a piece of trivia
 ///
 /// This does not directly influence how this content will be printed, but some
@@ -1079,6 +1102,10 @@ pub enum FormatElement {
     /// Delay the printing of its content until the next line break
     LineSuffix(Content),
 
+    /// Prevents that line suffixes move past this boundary. Forces the printer to print any pending
+    /// line suffixes, potentially by inserting a hard line break.
+    LineSuffixBoundary,
+
     /// Special semantic element letting the printer and formatter know this is
     /// a trivia content, and it should only have a limited influence on the
     /// formatting (for instance line breaks contained within will not cause
@@ -1163,6 +1190,7 @@ impl Debug for FormatElement {
             FormatElement::LineSuffix(content) => {
                 fmt.debug_tuple("LineSuffix").field(content).finish()
             }
+            FormatElement::LineSuffixBoundary => write!(fmt, "LineSuffixBoundary"),
             FormatElement::Comment(content) => fmt.debug_tuple("Comment").field(content).finish(),
             FormatElement::Verbatim(verbatim) => fmt
                 .debug_tuple("Verbatim")
@@ -1556,6 +1584,7 @@ impl FormatElement {
             FormatElement::LineSuffix(_) => false,
             FormatElement::Comment(content) => content.will_break(),
             FormatElement::Verbatim(verbatim) => verbatim.element.will_break(),
+            FormatElement::LineSuffixBoundary => false,
         }
     }
 

crates/rome_formatter/src/printer/mod.rs

@@ -6,7 +6,7 @@ use crate::format_element::{
     ConditionalGroupContent, Group, LineMode, List, PrintMode, VerbatimKind,
 };
 use crate::intersperse::Intersperse;
-use crate::{FormatElement, GroupId, Printed, SourceMarker, TextRange};
+use crate::{hard_line_break, FormatElement, GroupId, Printed, SourceMarker, TextRange};
 
 use crate::prelude::Line;
 use rome_rowan::TextSize;
@@ -221,6 +221,12 @@ impl<'a> Printer<'a> {
                     .line_suffixes
                     .push(PrintElementCall::new(&**suffix, args));
             }
+            FormatElement::LineSuffixBoundary => {
+                const HARD_BREAK: &FormatElement = &hard_line_break();
+                // enqueue a line break, this will flush the line suffix
+                queue.enqueue(PrintElementCall::new(HARD_BREAK, args));
+            }
+
             FormatElement::Comment(content) => {
                 queue.enqueue(PrintElementCall::new(content.as_ref(), args));
             }
@@ -597,6 +603,7 @@ fn fits_on_line<'a>(
         pending_indent: printer.state.pending_indent,
         pending_space: printer.state.pending_space,
         line_width: printer.state.line_width,
+        has_line_suffix: printer.state.line_suffixes.is_empty(),
     };
 
     let result = loop {
@@ -743,6 +750,14 @@ fn fits_element_on_line<'a, 'rest>(
             if args.mode.is_flat() {
                 return Fits::No;
             }
+
+            state.has_line_suffix = true;
+        }
+
+        FormatElement::LineSuffixBoundary => {
+            if state.has_line_suffix {
+                return Fits::No;
+            }
         }
 
         FormatElement::Comment(content) => queue.enqueue(PrintElementCall::new(content, args)),
@@ -779,6 +794,7 @@ impl From<bool> for Fits {
 struct MeasureState {
     pending_indent: u16,
     pending_space: bool,
+    has_line_suffix: bool,
     line_width: usize,
 }
 

crates/rome_js_formatter/tests/specs/prettier/js/comments/while.js.snap

@@ -1,8 +1,6 @@
 ---
 source: crates/rome_js_formatter/tests/prettier_tests.rs
-assertion_line: 121
 expression: while.js
-
 ---
 # Input
 ```js