feat(prettier) Add IndentIfBreak support (#1420)

crates/oxc_prettier/src/doc.rs

@@ -15,6 +15,7 @@ pub enum Doc<'a> {
     Array(Vec<'a, Doc<'a>>),
     /// Increase the level of indentation.
     Indent(Vec<'a, Doc<'a>>),
+    IndentIfBreak(Vec<'a, Doc<'a>>),
     /// Mark a group of items which the printer should try to fit on one line.
     /// This is the basic command to tell the printer when to break.
     /// Groups are usually nested, and the printer will try to fit everything on one line,
@@ -117,6 +118,17 @@ fn print_do_to_debug(doc: &Doc<'_>) -> std::string::String {
             }
             string.push_str("])");
         }
+        Doc::IndentIfBreak(contents) => {
+            string.push_str("indentIfBreak(");
+            string.push_str("[\n");
+            for (idx, doc) in contents.iter().enumerate() {
+                string.push_str(&print_do_to_debug(doc));
+                if idx != contents.len() - 1 {
+                    string.push_str(", ");
+                }
+            }
+            string.push_str("]) \n");
+        }
         Doc::Group(contents) => {
             string.push_str("group([\n");
             for (idx, doc) in contents.iter().enumerate() {

crates/oxc_prettier/src/macros.rs

@@ -35,6 +35,19 @@ macro_rules! indent {
     };
 }
 
+#[macro_export]
+macro_rules! indent_if_break {
+    ($p:ident, $( $x:expr ),* $(,)?) => {
+        {
+            let mut temp_vec = $p.vec();
+            $(
+                temp_vec.push($x);
+            )*
+            Doc::IndentIfBreak(temp_vec)
+        }
+    };
+}
+
 #[macro_export]
 macro_rules! line {
     () => {

crates/oxc_prettier/src/printer/mod.rs

@@ -52,6 +52,7 @@ impl<'a> Printer<'a> {
                 Doc::Array(docs) => self.handle_array(indent, mode, docs),
                 Doc::Indent(docs) => self.handle_indent(indent, mode, docs),
                 Doc::Group(docs) => self.handle_group(indent, mode, docs),
+                Doc::IndentIfBreak(docs) => self.handle_indent_if_break(indent, mode, docs),
                 Doc::Line => self.handle_line(indent, mode),
                 Doc::Softline => self.handle_softline(indent, mode),
                 Doc::Hardline => self.handle_hardline(indent),
@@ -102,6 +103,26 @@ impl<'a> Printer<'a> {
         }
     }
 
+    fn handle_indent_if_break(
+        &mut self,
+        indent: Indent,
+        mode: Mode,
+        docs: oxc_allocator::Vec<'a, Doc<'a>>,
+    ) {
+        match mode {
+            Mode::Flat => {
+                self.cmds.extend(
+                    docs.into_iter().rev().map(|doc| Command::new(indent, Mode::Flat, doc)),
+                );
+            }
+            Mode::Break => {
+                self.cmds.extend(docs.into_iter().rev().map(|doc| {
+                    Command::new(Indent { length: indent.length + 1 }, Mode::Flat, doc)
+                }));
+            }
+        }
+    }
+
     fn handle_line(&mut self, indent: Indent, mode: Mode) {
         if matches!(mode, Mode::Flat) {
             self.out.push(b' ');
@@ -146,7 +167,10 @@ impl<'a> Printer<'a> {
                 Doc::Str(string) => {
                     remaining_width -= string.len() as isize;
                 }
-                Doc::Array(docs) | Doc::Indent(docs) | Doc::Group(docs) => {
+                Doc::IndentIfBreak(docs)
+                | Doc::Array(docs)
+                | Doc::Indent(docs)
+                | Doc::Group(docs) => {
                     // Prepend docs to the queue
                     for d in docs.iter().rev() {
                         queue.push_front(d);