feat(compiler): support empty expression for event with modifiers

Author: zhiyuanzmj

packages/compiler/src/transforms/transformElement.ts

@@ -262,6 +262,7 @@ function transformProp(
 
   if (
     !isDirectiveRegex.test(name) &&
+    !isEventRegex.test(name) &&
     (!prop.value || prop.value.type === 'StringLiteral')
   ) {
     if (isReservedProp(name)) return

packages/compiler/test/transforms/__snapshots__/vOn.spec.ts.snap

@@ -55,3 +55,89 @@ exports[`v-on > event modifier 1`] = `
   return [n1, n3, n5, n7, n9, n11, n13, n15, n17, n19, n21, n23, n25, n27, n29, n31, n33, n35, n37, n39, n41, n43]
 "
 `;
+
+exports[`v-on > should delegate event 1`] = `
+"import { delegateEvents as _delegateEvents, template as _template } from 'vue';
+const t0 = _template("<div></div>", true)
+_delegateEvents("click")
+
+export function render(_ctx) {
+  const n0 = t0()
+  n0.$evtclick = e => _ctx.test(e)
+  return n0
+}"
+`;
+
+exports[`v-on > should not wrap keys guard if no key modifier is present 1`] = `
+"
+  const n0 = t0()
+  n0.$evtkeyup = _withModifiers(e => test(e), ["exact"])
+  return n0
+"
+`;
+
+exports[`v-on > should support multiple modifiers and event options w/ prefixIdentifiers: true 1`] = `
+"
+  const n0 = t0()
+  _on(n0, "click", _withModifiers(e => test(e), ["stop","prevent"]), {
+    capture: true, 
+    once: true
+  })
+  return n0
+"
+`;
+
+exports[`v-on > should transform click.middle 1`] = `
+"import { withModifiers as _withModifiers, delegateEvents as _delegateEvents, template as _template } from 'vue';
+const t0 = _template("<div></div>", true)
+_delegateEvents("mouseup")
+
+export function render(_ctx) {
+  const n0 = t0()
+  n0.$evtmouseup = _withModifiers(e => _ctx.test(e), ["middle"])
+  return n0
+}"
+`;
+
+exports[`v-on > should transform click.right 1`] = `
+"import { withModifiers as _withModifiers, delegateEvents as _delegateEvents, template as _template } from 'vue';
+const t0 = _template("<div></div>", true)
+_delegateEvents("contextmenu")
+
+export function render(_ctx) {
+  const n0 = t0()
+  n0.$evtcontextmenu = _withModifiers(e => _ctx.test(e), ["right"])
+  return n0
+}"
+`;
+
+exports[`v-on > should use delegate helper when have multiple events of same name 1`] = `
+"import { delegate as _delegate, withModifiers as _withModifiers, delegateEvents as _delegateEvents, template as _template } from 'vue';
+const t0 = _template("<div></div>", true)
+_delegateEvents("click")
+
+export function render(_ctx) {
+  const n0 = t0()
+  _delegate(n0, "click", e => _ctx.test(e))
+  _delegate(n0, "click", _withModifiers(e => _ctx.test(e), ["stop"]))
+  return n0
+}"
+`;
+
+exports[`v-on > should wrap keys guard for keyboard events or dynamic events 1`] = `
+"
+  const n0 = t0()
+  _on(n0, "keydown", _withKeys(_withModifiers(e => test(e), ["stop","ctrl"]), ["a"]), {
+    capture: true
+  })
+  return n0
+"
+`;
+
+exports[`v-on > should wrap keys guard for static key event w/ left/right modifiers 1`] = `
+"
+  const n0 = t0()
+  n0.$evtkeyup = _withKeys(e => test(e), ["left"])
+  return n0
+"
+`;