fix(js_formatter): placement of comments inside default switch clause

CHANGELOG.md

@@ -22,6 +22,8 @@ Read our [guidelines for writing a good changelog entry](https://github.com/biom
 
 #### Bug fixes
 
+- Fix [#1170](https://github.com/biomejs/biome/issues/1170). Fix placement of comments inside default switch clause. Now all line comments that has a preceding node will keep their position. Contributed by @kalleep
+
 ### JavaScript APIs
 
 ### Linter

crates/biome_js_formatter/src/comments.rs

@@ -330,22 +330,39 @@ fn handle_continue_break_comment(
 ///     }
 /// ```
 ///
-/// All other same line comments become `Dangling` comments that are handled inside of the default case
-/// formatting
+/// All other same line comments will use `Default` placement if they have a perceding node.
+/// ```javascript
+/// switch(x) {
+///     default:
+///         a(); // asd
+///         break;
+/// }
+/// ```
+///
+/// All other comments become `Dangling` comments that are handled inside of the default case
+/// formatting.
 fn handle_switch_default_case_comment(
     comment: DecoratedComment<JsLanguage>,
 ) -> CommentPlacement<JsLanguage> {
-    match (comment.enclosing_node().kind(), comment.following_node()) {
-        (JsSyntaxKind::JS_DEFAULT_CLAUSE, Some(following)) => {
-            match JsBlockStatement::cast_ref(following) {
-                Some(block) if comment.kind().is_line() => {
-                    place_block_statement_comment(block, comment)
-                }
-                _ => CommentPlacement::dangling(comment.enclosing_node().clone(), comment),
-            }
-        }
-        _ => CommentPlacement::Default(comment),
+    if comment.enclosing_node().kind() != JsSyntaxKind::JS_DEFAULT_CLAUSE {
+        return CommentPlacement::Default(comment);
     }
+
+    if !comment.kind().is_line() {
+        return CommentPlacement::dangling(comment.enclosing_node().clone(), comment);
+    }
+
+    let Some(block) = comment
+        .following_node()
+        .and_then(JsBlockStatement::cast_ref)
+    else {
+        if comment.preceding_node().is_some() {
+            return CommentPlacement::Default(comment);
+        }
+        return CommentPlacement::dangling(comment.enclosing_node().clone(), comment);
+    };
+
+    place_block_statement_comment(block, comment)
 }
 
 fn handle_labelled_statement_comment(

crates/biome_js_formatter/tests/specs/js/module/statement/switch_comment.js

@@ -0,0 +1,18 @@
+switch(5){default: // comment5
+// comment5a
+foo();bar();//comment5b
+break;// comment5c
+}
+
+switch(x) {
+  default:
+    a(); // asd
+    break;
+}
+
+switch(x) {
+  default:
+    // a
+    a(); // ab
+    break;
+}

crates/biome_js_formatter/tests/specs/js/module/statement/switch_comment.js.snap

@@ -0,0 +1,75 @@
+---
+source: crates/biome_formatter_test/src/snapshot_builder.rs
+info: js/module/statement/switch_comment.js
+---
+
+# Input
+
+```js
+switch(5){default: // comment5
+// comment5a
+foo();bar();//comment5b
+break;// comment5c
+}
+
+switch(x) {
+  default:
+    a(); // asd
+    break;
+}
+
+switch(x) {
+  default:
+    // a
+    a(); // ab
+    break;
+}
+
+```
+
+
+=============================
+
+# Outputs
+
+## Output 1
+
+-----
+Indent style: Tab
+Indent width: 2
+Line ending: LF
+Line width: 80
+Quote style: Double Quotes
+JSX quote style: Double Quotes
+Quote properties: As needed
+Trailing comma: All
+Semicolons: Always
+Arrow parentheses: Always
+Bracket spacing: true
+Bracket same line: false
+-----
+
+```js
+switch (5) {
+	default: // comment5
+		// comment5a
+		foo();
+		bar(); //comment5b
+		break; // comment5c
+}
+
+switch (x) {
+	default:
+		a(); // asd
+		break;
+}
+
+switch (x) {
+	default:
+		// a
+		a(); // ab
+		break;
+}
+```
+
+

crates/biome_js_formatter/tests/specs/prettier/js/switch/comments2.js

@@ -14,10 +14,8 @@ switch(4){default: // comment4
 break;// comment4b
 }
 
-// FIXME
-// TODO: reformat issue
-// switch(5){default: // comment5
-// // comment5a
-// foo();bar();//comment5b
-// break;// comment5c
-// }
+switch(5){default: // comment5
+ // comment5a
+ foo();bar();//comment5b
+ break;// comment5c
+}

website/src/content/docs/internals/changelog.mdx

@@ -28,6 +28,8 @@ Read our [guidelines for writing a good changelog entry](https://github.com/biom
 
 #### Bug fixes
 
+- Fix [#1170](https://github.com/biomejs/biome/issues/1170). Fix placement of comments inside default switch clause. Now all line comments that has a preceding node will keep their position. Contributed by @kalleep
+
 ### JavaScript APIs
 
 ### Linter