feat(compiler-core): more hoisting optimizations

[HcySunYang]

This PR enhances hoisting optimization:

1. Dynamic attribute with static value:

<div><span :foo="0"></span></div>

Before:

import { createVNode, createBlock, openBlock } from "vue"

export default function render() {
  const _ctx = this
  return (openBlock(), createBlock("div", null, [
    createVNode("span", { foo: 0 }, null, 8 /* PROPS */, ["foo"])
  ]))
}

Now:

import { createVNode, createBlock, openBlock } from "vue"

const _hoisted_1 = createVNode("span", { foo: 0 })

export default function render() {
  const _ctx = this
  return (openBlock(), createBlock("div", null, [
    _hoisted_1
  ]))
}

2. Static interpolation:

<div><span>{{ 1 + 2 }}</span></div>

Before:

import { toString, createVNode, createBlock, openBlock } from "vue"

export default function render() {
  const _ctx = this
  return (openBlock(), createBlock("div", null, [
    createVNode("span", null, toString(1 + 2), 1 /* TEXT */)
  ]))
}

Now:

import { toString, createVNode, createBlock, openBlock } from "vue"
// Maybe patchFlag can be removed.
const _hoisted_1 = createVNode("span", null, toString(1 + 2), 1 /* TEXT */)

export default function render() {
  const _ctx = this
  return (openBlock(), createBlock("div", null, [
    _hoisted_1
  ]))
}

3. Write inline styles/class for better performance:

<div><span :class="{ foo: true }">{{ bar }}</span></div>

Before:

import { toString, createVNode, createBlock, openBlock } from "vue"

export default function render() {
  const _ctx = this
  return (openBlock(), createBlock("div", null, [
    createVNode("span", { class: { foo: true }}, toString(_ctx.bar), 3 /* TEXT, CLASS */)
  ]))
}

Now:

import { toString, createVNode, createBlock, openBlock } from "vue"

const _hoisted_1 = { class: { foo: true }}

export default function render() {
  const _ctx = this
  return (openBlock(), createBlock("div", null, [
    createVNode("span", _hoisted_1, toString(_ctx.bar), 1 /* TEXT */)
  ]))
}

This can avoid class being patched.

If there is a more suitable implementation, or if this feature does not match the plan, or for other reasons, then this PR can be closed at any time, thanks

[vue-bot]

Hey @HcySunYang, thank you for your time and effort spent on this PR, contributions like yours help make Vue better for everyone. Cheers! 💚

[yyx990803]

Great work!