fix(formatter): correct printing comments for assignment pattern (#14469)

Author: Dunqing

crates/oxc_formatter/src/write/mod.rs

@@ -857,17 +857,14 @@ impl<'a> FormatWrite<'a> for AstNode<'a, BindingPattern<'a>> {
 
 impl<'a> FormatWrite<'a> for AstNode<'a, AssignmentPattern<'a>> {
     fn write(&self, f: &mut Formatter<'_, 'a>) -> FormatResult<()> {
+        let mut left = self.left().memoized();
+        // Format `left` early before writing leading comments, so that comments
+        // inside `left` are not treated as leading comments of `= right`
+        left.inspect(f)?;
         let comments = f.context().comments().own_line_comments_before(self.right.span().start);
         write!(
             f,
-            [
-                FormatLeadingComments::Comments(comments),
-                self.left(),
-                space(),
-                "=",
-                space(),
-                self.right(),
-            ]
+            [FormatLeadingComments::Comments(comments), left, space(), "=", space(), self.right()]
         )
     }
 }

crates/oxc_formatter/tests/fixtures/js/comments/assignment-pattern.js

@@ -0,0 +1,13 @@
+({
+  // comment1 inside the left side of the assignment pattern
+  random = Math.random,
+  // comment2 inside the left side of the assignment pattern
+  sqrt = Math.sqrt,
+} = {}) => {};
+
+([
+  // comment1 inside the left side of the assignment pattern
+  random = Math.random,
+  // comment2 inside the left side of the assignment pattern
+  sqrt = Math.sqrt,
+] = []) => {};

crates/oxc_formatter/tests/fixtures/js/comments/assignment-pattern.js.snap

@@ -0,0 +1,34 @@
+---
+source: crates/oxc_formatter/tests/fixtures/mod.rs
+---
+==================== Input ====================
+({
+  // comment1 inside the left side of the assignment pattern
+  random = Math.random,
+  // comment2 inside the left side of the assignment pattern
+  sqrt = Math.sqrt,
+} = {}) => {};
+
+([
+  // comment1 inside the left side of the assignment pattern
+  random = Math.random,
+  // comment2 inside the left side of the assignment pattern
+  sqrt = Math.sqrt,
+] = []) => {};
+
+==================== Output ====================
+({
+  // comment1 inside the left side of the assignment pattern
+  random = Math.random,
+  // comment2 inside the left side of the assignment pattern
+  sqrt = Math.sqrt,
+} = {}) => {};
+
+([
+  // comment1 inside the left side of the assignment pattern
+  random = Math.random,
+  // comment2 inside the left side of the assignment pattern
+  sqrt = Math.sqrt,
+] = []) => {};
+
+===================== End =====================

crates/oxc_formatter/tests/fixtures/mod.rs

@@ -198,7 +198,6 @@ fn generate_snapshot(path: &Path, source_text: &str) -> String {
 }
 
 /// Helper function to run a test for a single file
-#[expect(unused)]
 fn test_file(path: &Path) {
     let source_text = fs::read_to_string(path).unwrap();
     let snapshot = generate_snapshot(path, &source_text);