error on unclosed comments and blocks with only whitespace

src/parse/index.ts

@@ -112,14 +112,14 @@ export class Parser {
 		throw new ParseError(message, this.template, index, this.filename);
 	}
 
-	eat(str: string, required?: boolean) {
+	eat(str: string, required?: boolean, message?: string) {
 		if (this.match(str)) {
 			this.index += str.length;
 			return true;
 		}
 
 		if (required) {
-			this.error(`Expected ${str}`);
+			this.error(message || `Expected ${str}`);
 		}
 
 		return false;

src/parse/state/mustache.ts

@@ -5,6 +5,13 @@ import reservedNames from '../../utils/reservedNames';
 import { Parser } from '../index';
 import { Node } from '../../interfaces';
 
+function isEmpty(nodes: Node[]) {
+	if (!nodes || nodes.length > 1) return false;
+	if (nodes.length === 0) return true;
+	if (nodes.length > 1) return false;
+	return nodes[0].type === 'Text' && !/\S/.test(nodes[0].data);
+}
+
 function trimWhitespace(block: Node, trimBefore: boolean, trimAfter: boolean) {
 	if (!block.children) return; // AwaitBlock
 
@@ -74,7 +81,7 @@ export default function mustache(parser: Parser) {
 		}
 
 		// strip leading/trailing whitespace as necessary
-		if (block.children && !block.children.length) parser.error(`Empty block`, block.start);
+		if (isEmpty(block.children)) parser.error(`Empty block`, block.start);
 
 		const charBefore = parser.template[block.start - 1];
 		const charAfter = parser.template[parser.index];

src/parse/state/tag.ts

@@ -71,7 +71,7 @@ export default function tag(parser: Parser) {
 
 	if (parser.eat('!--')) {
 		const data = parser.readUntil(/-->/);
-		parser.eat('-->');
+		parser.eat('-->', true, 'comment was left open, expected -->');
 
 		parser.current().children.push({
 			start,

test/parser/samples/error-comment-unclosed/error.json

@@ -1,8 +1,8 @@
 {
-	"message": "comment was left open",
+	"message": "comment was left open, expected -->",
 	"loc": {
 		"line": 1,
-		"column": 0
+		"column": 24
 	},
-	"pos": 0
+	"pos": 24
 }

test/parser/samples/error-each-blocks-keyed-whitespace/input.html

@@ -1,11 +1,11 @@
 {{#each foos as foo @id}}
 {{/each}}
 <script>
-  export default {
-    data: () => ({
-      foos: [
-        { "id": 5 }
-      ]
-    })
-  };
+	export default {
+		data: () => ({
+			foos: [
+				{ id: 5 }
+			]
+		})
+	};
 </script>