parse @id for keyed each blocks (#81)

Author: Rich-Harris

src/parse/state/mustache.js

@@ -171,6 +171,12 @@ export default function mustache ( parser ) {
 				if ( !block.index ) parser.error( `Expected name` );
 				parser.allowWhitespace();
 			}
+
+			if ( parser.eat( '@' ) ) {
+				block.key = parser.read( validIdentifier );
+				if ( !block.key ) parser.error( `Expected name` );
+				parser.allowWhitespace();
+			}
 		}
 
 		parser.eat( '}}', true );

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

@@ -0,0 +1,3 @@
+{{#each todos as todo @id}}
+	<p>{{todo}}</p>
+{{/each}}

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

@@ -0,0 +1,46 @@
+{
+	"html": {
+		"start": 0,
+		"end": 54,
+		"type": "Fragment",
+		"children": [
+			{
+				"start": 0,
+				"end": 54,
+				"type": "EachBlock",
+				"expression": {
+					"start": 8,
+					"end": 13,
+					"type": "Identifier",
+					"name": "todos"
+				},
+				"context": "todo",
+				"key": "id",
+				"children": [
+					{
+						"start": 29,
+						"end": 44,
+						"type": "Element",
+						"name": "p",
+						"attributes": [],
+						"children": [
+							{
+								"start": 32,
+								"end": 40,
+								"type": "MustacheTag",
+								"expression": {
+									"start": 34,
+									"end": 38,
+									"type": "Identifier",
+									"name": "todo"
+								}
+							}
+						]
+					}
+				]
+			}
+		]
+	},
+	"css": null,
+	"js": null
+}