All files / compiler-core/src/transforms vOnce.ts

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import type { NodeTransform } from '../transform'
import { findDir } from '../utils'
import { type ElementNode, type ForNode, type IfNode, NodeTypes } from '../ast'
import { SET_BLOCK_TRACKING } from '../runtimeHelpers'
 
const seen = new WeakSet()
 
export const transformOnce: NodeTransform = (node, context) => {
  if (node.type === NodeTypes.ELEMENT && findDir(node, 'once', true)) {
    if (seen.has(node) || context.inVOnce || context.inSSR) {
      return
    }
    seen.add(node)
    context.inVOnce = true
    context.helper(SET_BLOCK_TRACKING)
    return () => {
      context.inVOnce = false
      const cur = context.currentNode as ElementNode | IfNode | ForNode
      if (cur.codegenNode) {
        cur.codegenNode = context.cache(cur.codegenNode, true /* isVNode */)
      }
    }
  }
}