How to use the @vue/shared.PatchFlags.CLASS function in @vue/shared

// single v-bind with nothing else - no need for a mergeProps call
      propsExpression = mergeArgs[0]
    }
  } else if (properties.length) {
    propsExpression = createObjectExpression(
      dedupeProperties(properties),
      elementLoc
    )
  }

  // patchFlag analysis
  if (hasDynamicKeys) {
    patchFlag |= PatchFlags.FULL_PROPS
  } else {
    if (hasClassBinding) {
      patchFlag |= PatchFlags.CLASS
    }
    if (hasStyleBinding) {
      patchFlag |= PatchFlags.STYLE
    }
    if (dynamicPropNames.length) {
      patchFlag |= PatchFlags.PROPS
    }
  }
  if (patchFlag === 0 && (hasRef || runtimeDirectives.length > 0)) {
    patchFlag |= PatchFlags.NEED_PATCH
  }

  return {
    props: propsExpression,
    directives: runtimeDirectives,
    patchFlag,

if (patchFlag & PatchFlags.FULL_PROPS) {
        // element props contain dynamic keys, full diff needed
        patchProps(
          el,
          n2,
          oldProps,
          newProps,
          parentComponent,
          parentSuspense,
          isSVG
        )
      } else {
        // class
        // this flag is matched when the element has dynamic class bindings.
        if (patchFlag & PatchFlags.CLASS) {
          if (oldProps.class !== newProps.class) {
            hostPatchProp(el, 'class', newProps.class, null, isSVG)
          }
        }

        // style
        // this flag is matched when the element has dynamic style bindings
        if (patchFlag & PatchFlags.STYLE) {
          hostPatchProp(el, 'style', newProps.style, oldProps.style, isSVG)
        }

        // props
        // This flag is matched when the element has dynamic prop/attr bindings
        // other than class and style. The keys of dynamic prop/attrs are saved for
        // faster iteration.
        // Note dynamic keys like :[foo]="bar" will cause this optimization to

// single v-bind with nothing else - no need for a mergeProps call
      propsExpression = mergeArgs[0]
    }
  } else if (properties.length) {
    propsExpression = createObjectExpression(
      dedupeProperties(properties),
      elementLoc
    )
  }

  // patchFlag analysis
  if (hasDynamicKeys) {
    patchFlag |= PatchFlags.FULL_PROPS
  } else {
    if (hasClassBinding) {
      patchFlag |= PatchFlags.CLASS
    }
    if (hasStyleBinding) {
      patchFlag |= PatchFlags.STYLE
    }
    if (dynamicPropNames.length) {
      patchFlag |= PatchFlags.PROPS
    }
  }
  if (patchFlag === 0 && (hasRef || runtimeDirectives.length > 0)) {
    patchFlag |= PatchFlags.NEED_PATCH
  }

  return {
    props: propsExpression,
    directives: runtimeDirectives,
    patchFlag,

test('CLASS + STYLE + PROPS', () => {
      const { node } = parseWithBind(
        `<div id="foo">`
      )
      expect(node.arguments.length).toBe(5)
      expect(node.arguments[3]).toBe(
        genFlagText([PatchFlags.CLASS, PatchFlags.STYLE, PatchFlags.PROPS])
      )
      expect(node.arguments[4]).toBe(`["foo", "baz"]`)
    })
</div>

test('CLASS', () => {
      const { node } = parseWithBind(`<div>`)
      expect(node.arguments.length).toBe(4)
      expect(node.arguments[3]).toBe(genFlagText(PatchFlags.CLASS))
    })
</div>