vue3-yuanma/packages/compiler-core/src/transforms/vOnce.ts

import { NodeTransform } from '../transform'
import { findDir } from '../utils'
import { NodeTypes } from '../ast'
import { SET_BLOCK_TRACKING } from '../runtimeHelpers'

export const transformOnce: NodeTransform = (node, context) => {
  if (node.type === NodeTypes.ELEMENT && findDir(node, 'once', true)) {
    context.helper(SET_BLOCK_TRACKING)
    return () => {
      if (node.codegenNode) {
        node.codegenNode = context.cache(node.codegenNode, true /* isVNode */)
      }
    }
  }
}