sparse array patterns

src/parse/read/context.ts

@@ -46,8 +46,13 @@ export default function readContext(parser: Parser) {
 
 		do {
 			parser.allowWhitespace();
-			context.elements.push(readContext(parser));
+
-			parser.allowWhitespace();
+			if (parser.template[parser.index] === ',') {
+				context.elements.push(null);
+			} else {
+				context.elements.push(readContext(parser));
+				parser.allowWhitespace();
+			}
 		} while (parser.eat(','));
 
 		errorOnAssignmentPattern(parser);

src/utils/unpackDestructuring.ts

@@ -3,6 +3,8 @@ export default function unpackDestructuring(
 	node: Node,
 	tail: string
 ) {
+	if (!node) return;
+
 	if (node.type === 'Identifier') {
 		contexts.push({
 			key: node,

test/runtime/samples/each-block-destructured-array-sparse/_config.js

@@ -0,0 +1,20 @@
+export default {
+	data: {
+		animalPawsEntries: [
+			['raccoon', 'hands'],
+			['eagle', 'wings']
+		]
+	},
+
+	html: `
+		<p>hands</p>
+		<p>wings</p>
+	`,
+
+	test ( assert, component, target ) {
+		component.set({ animalPawsEntries: [['foo', 'bar']] });
+		assert.htmlEqual( target.innerHTML, `
+			<p>bar</p>
+		`);
+	},
+};

test/runtime/samples/each-block-destructured-array-sparse/main.html

@@ -0,0 +1,3 @@
+{#each animalPawsEntries as [, pawType]}
+	<p>{pawType}</p>
+{/each}