throw qweb error if invalid loop in t-foreach

web/static/src/ts/core/qweb_vdom.ts

@@ -644,6 +644,9 @@ const forEachDirective: Directive = {
     const name = node.getAttribute("t-as")!;
     let arrayID = ctx.generateID();
     ctx.addLine(`let _${arrayID} = ${qweb._formatExpression(elems)};`);
+    ctx.addLine(
+      `if (!_${arrayID}) { throw new Error('QWeb error: Invalid loop expression')}`
+    );
     ctx.addLine(
       `if (typeof _${arrayID} === 'number') { _${arrayID} = Array.from(Array(_${arrayID}).keys())}`
     );

web/static/tests/core/qweb_vdom.test.ts

@@ -545,6 +545,14 @@ describe("foreach", () => {
     renderToString(qweb, "test", context);
     expect(Object.keys(context).length).toBe(0);
   });
+
+  test("throws error if invalid loop expression", () => {
+    qweb.addTemplate(
+      "test",
+      `<div><t t-foreach="abc" t-as="item"><span/></t></div>`
+    );
+    expect(() => qweb.render("test")).toThrow("Invalid loop expression");
+  });
 });
 
 describe("misc", () => {