[IMP] qweb: crash if t-on directive is used with no event

closes #33

src/qweb.ts

@@ -932,6 +932,9 @@ const onDirective: Directive = {
   atNodeCreation({ ctx, fullName, value, nodeID }) {
     ctx.rootContext.shouldDefineOwner = true;
     const eventName = fullName.slice(5);
+    if (!eventName) {
+      throw new Error("Missing event name with t-on directive");
+    }
     let extraArgs;
     let handler = value.replace(/\(.*\)/, function(args) {
       extraArgs = args.slice(1, -1);

tests/qweb.test.ts

@@ -115,6 +115,13 @@ describe("error handling", () => {
     );
   });
 
+  test("nice error when t-on is evaluated with a missing event", () => {
+    qweb.addTemplate("templatename", `<div t-on="somemethod"></div>`);
+    expect(() =>
+      qweb.render("templatename", { someMethod() {} }, { handlers: [] })
+    ).toThrow("Missing event name with t-on directive");
+  });
+
   test("error when compiled code is invalid", () => {
     qweb.addTemplate(
       "templatename",