Function createChildrenCodegenNode

packages/compiler-core/src/transforms/vIf.ts:240–304

(
  branch: IfBranchNode,
  keyIndex: number,
  context: TransformContext,
)

}

function createChildrenCodegenNode(
  branch: IfBranchNode,
  keyIndex: number,
  context: TransformContext,
): BlockCodegenNode | MemoExpression {
  const { helper } = context
  const keyProperty = createObjectProperty(
    `key`,
    createSimpleExpression(
      `${keyIndex}`,
      false,
      locStub,
      ConstantTypes.CAN_CACHE,
    ),
  )
  const { children } = branch
  const firstChild = children[0]
  const needFragmentWrapper =
    children.length !== 1 || firstChild.type !== NodeTypes.ELEMENT
  if (needFragmentWrapper) {
    if (children.length === 1 && firstChild.type === NodeTypes.FOR) {
      // optimize away nested fragments when child is a ForNode
      const vnodeCall = firstChild.codegenNode!
      injectProp(vnodeCall, keyProperty, context)
      return vnodeCall
    } else {
      let patchFlag = PatchFlags.STABLE_FRAGMENT
      // check if the fragment actually contains a single valid child with
      // the rest being comments
      if (
        __DEV__ &&
        !branch.isTemplateIf &&
        children.filter(c => c.type !== NodeTypes.COMMENT).length === 1
      ) {
        patchFlag |= PatchFlags.DEV_ROOT_FRAGMENT
      }

      return createVNodeCall(
        context,
        helper(FRAGMENT),
        createObjectExpression([keyProperty]),
        children,
        patchFlag,
        undefined,
        undefined,
        true,
        false,
        false /* isComponent */,
        branch.loc,
      )
    }
  } else {
    const ret = (firstChild as ElementNode).codegenNode as
      | BlockCodegenNode
      | MemoExpression
    const vnodeCall = getMemoedVNodeCall(ret)
    // Change createVNode to createBlock.
    if (vnodeCall.type === NodeTypes.VNODE_CALL) {