support multiple trailing comments after last statement in a body

Author: dummdidumm

packages/svelte/src/compiler/phases/1-parse/acorn.js

@@ -104,23 +104,43 @@ function get_comment_handlers(source) {
 					next();
 
 					if (comments[0]) {
-						const parent = path.at(-1);
+						const parent = /** @type {any} */ (path.at(-1));
 
 						if (parent === undefined || node.end !== parent.end) {
 							const slice = source.slice(node.end, comments[0].start);
-
-							if (node.end <= comments[0].start && /^[,) \t]*$/.test(slice)) {
+							const is_last_in_body =
+								// BlockStatement and Program nodes have a body property
+								parent?.body?.length &&
+								Array.isArray(parent?.body) &&
+								parent.body.indexOf(node) === parent.body.length - 1;
+
+							if (is_last_in_body) {
+								// Special case: There can be multiple trailing comments after the last node in a block,
+								// and they can be separated by newlines
+								let end = node.end;
+
+								while (comments.length) {
+									const comment = comments[0];
+									if (parent && comment.start > parent.end) break;
+
+									const slice = source.slice(end, comment.start);
+									if (node.end === end ? !/^[,)\s]*$/.test(slice) : slice.trim() !== '') break;
+
+									(node.trailingComments ||= []).push(comment);
+									comments.shift();
+									end = comment.end;
+								}
+							} else if (node.end <= comments[0].start && /^[,) \t]*$/.test(slice)) {
 								node.trailingComments = [/** @type {CommentWithLocation} */ (comments.shift())];
 							}
 						}
 					}
 				}
 			});
 
-			// Special case: Trailing comments after the root node (which can only happen for expression tags) get added
-			// regardless of line breaks between the root node and the comments. This ensures that we can later detect
-			// the end of the expression tag correctly.
-			if (comments.length > 0 && comments[0].start >= ast.end) {
+			// Special case: Trailing comments after the root node (which can only happen for expression tags or for Program nodes).
+			// Adding them ensures that we can later detect the end of the expression tag correctly.
+			if (comments.length > 0 && (comments[0].start >= ast.end || ast.type === 'Program')) {
 				(ast.trailingComments ||= []).push(...comments.splice(0));
 			}
 		}

packages/svelte/tests/parser-legacy/samples/javascript-comments/input.svelte

@@ -5,8 +5,14 @@
 
 	/** a comment */
 	function asd() {
-		foo;
-		/* comment belonging to noone */
+		foo; // trailing
+		/* leading comment 1 */
+		/* leading comment 2 */
+		/* leading comment 3 */
+		bar;
+		/* trailing comment 1 */
+		/* trailing comment 2 */
+		/* trailing comment 3 */
 	}
 </script>
 
@@ -15,7 +21,7 @@
 	() => {
 		/* another comment */
 		fn(); // a trailing comment
-		/* comment belonging to noone */
+		/* trailing block comment */
 	}}
 >
 {/* leading block comment */ a}