update keyed each block syntax

Author: Rich-Harris

src/parse/state/mustache.ts

@@ -274,8 +274,8 @@ export default function mustache(parser: Parser) {
 				parser.allowWhitespace();
 			}
 
-			if (parser.eat('key')) {
-				parser.requireWhitespace();
+			if (parser.eat('(')) {
+				parser.allowWhitespace();
 
 				const expression = readExpression(parser);
 
@@ -292,6 +292,8 @@ export default function mustache(parser: Parser) {
 
 				block.key = expression.property.name;
 				parser.allowWhitespace();
+				parser.eat(')', true);
+				parser.allowWhitespace();
 			} else if (parser.eat('@')) {
 				block.key = parser.readIdentifier();
 				if (!block.key) parser.error(`Expected name`);

test/parser/samples/each-block-keyed/input-v2.html

@@ -1,3 +1,3 @@
-{#each todos as todo key todo.id}
+{#each todos as todo (todo.id)}
 	<p>{todo}</p>
 {/each}

test/parser/samples/each-block-keyed/output-v2.json

@@ -1,13 +1,13 @@
 {
-	"hash": "3sm0ec",
+	"hash": "1x6az5m",
 	"html": {
 		"start": 0,
-		"end": 56,
+		"end": 54,
 		"type": "Fragment",
 		"children": [
 			{
 				"start": 0,
-				"end": 56,
+				"end": 54,
 				"type": "EachBlock",
 				"expression": {
 					"type": "Identifier",
@@ -17,20 +17,20 @@
 				},
 				"children": [
 					{
-						"start": 35,
-						"end": 48,
+						"start": 33,
+						"end": 46,
 						"type": "Element",
 						"name": "p",
 						"attributes": [],
 						"children": [
 							{
-								"start": 38,
-								"end": 44,
+								"start": 36,
+								"end": 42,
 								"type": "MustacheTag",
 								"expression": {
 									"type": "Identifier",
-									"start": 39,
-									"end": 43,
+									"start": 37,
+									"end": 41,
 									"name": "todo"
 								}
 							}

test/runtime/samples/each-block-keyed/main-v2.html

@@ -0,0 +1,3 @@
+{#each todos as todo, i (todo.id)}
+	<p>{i+1}: {todo.description}</p>
+{/each}