throw if default export is not an object literal

src/validate/js/index.js

@@ -17,23 +17,22 @@ export default function validateJs ( validator, js ) {
 
 		if ( node.type === 'ExportDefaultDeclaration' ) {
 			if ( validator.defaultExport ) {
-				validator.error( `Duplicate default export`, node.start );
+				return validator.error( `Duplicate default export`, node.start );
 			}
 
-			validator.defaultExport = node;
+			if ( node.declaration.type !== 'ObjectExpression' ) {
+				return validator.error( `Default export must be an object literal`, node.declaration.start );
 			}
-	});
 
-	// ensure all exported props are valid
-	if ( validator.defaultExport ) {
-		checkForComputedKeys( validator, validator.defaultExport.declaration.properties );
-		checkForDupes( validator, validator.defaultExport.declaration.properties );
+			checkForComputedKeys( validator, node.declaration.properties );
+			checkForDupes( validator, node.declaration.properties );
 
-		validator.defaultExport.declaration.properties.forEach( prop => {
+			node.declaration.properties.forEach( prop => {
 				validator.templateProperties[ prop.key.name ] = prop;
 			});
 
-		validator.defaultExport.declaration.properties.forEach( prop => {
+			// ensure all exported props are valid
+			node.declaration.properties.forEach( prop => {
 				const propValidator = propValidators[ prop.key.name ];
 
 				if ( propValidator ) {
@@ -54,5 +53,8 @@ export default function validateJs ( validator, js ) {
 				const ns = validator.templateProperties.namespace.value.value;
 				validator.namespace = namespaces[ ns ] || ns;
 			}
+
+			validator.defaultExport = node;
 		}
+	});
 }

test/validator/export-default-must-be-object/errors.json

@@ -0,0 +1,8 @@
+[{
+	"message": "Default export must be an object literal",
+	"pos": 25,
+	"loc": {
+		"line": 2,
+		"column": 16
+	}
+}]

test/validator/export-default-must-be-object/input.html

@@ -0,0 +1,3 @@
+<script>
+	export default potato;
+</script>