fix: preserve commas in array expressions

fixes #432

Author: dummdidumm

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## 3.2.7 (unreleased)
 
 -   (fix) force quote style inside style directives
+-   (fix) preserve commas in array expressions
 -   (fix) Svelte 5: properly determine end of snippet parameters with TS annotations
 
 ## 3.2.6

src/print/index.ts

@@ -1206,7 +1206,16 @@ function _expandNode(node: any, parent?: any): string {
     switch (node.type) {
         case 'ArrayExpression':
         case 'ArrayPattern':
-            return ' [' + node.elements.map(_expandNode).join(',').slice(1) + ']';
+            return (
+                ' [' +
+                node.elements
+                    // handle null specifically here; else it would become the empty string, but that would mean
+                    // fewer elements in the array, which would change the meaning of the array
+                    .map((el: any) => (el === null ? ' ' : _expandNode(el)))
+                    .join(',')
+                    .slice(1) +
+                ']'
+            );
         case 'AssignmentPattern':
             return _expandNode(node.left) + ' =' + _expandNode(node.right);
         case 'Identifier':

test/printer/samples/each-block-destructured.html

@@ -1,3 +1,7 @@
 {#each animals as [key, value]}
     <p>{key}: {value}</p>
 {/each}
+
+{#each animals as [, value]}
+    <p>{value}</p>
+{/each}