Function parseForExpression

packages/compiler-core/src/parser.ts:496–567

(
  input: SimpleExpressionNode,
)

const stripParensRE = /^\(|\)$/g

function parseForExpression(
  input: SimpleExpressionNode,
): ForParseResult | undefined {
  const loc = input.loc
  const exp = input.content
  const inMatch = exp.match(forAliasRE)
  if (!inMatch) return

  const [, LHS, RHS] = inMatch

  const createAliasExpression = (
    content: string,
    offset: number,
    asParam = false,
  ) => {
    const start = loc.start.offset + offset
    const end = start + content.length
    return createExp(
      content,
      false,
      getLoc(start, end),
      ConstantTypes.NOT_CONSTANT,
      asParam ? ExpParseMode.Params : ExpParseMode.Normal,
    )
  }

  const result: ForParseResult = {
    source: createAliasExpression(RHS.trim(), exp.indexOf(RHS, LHS.length)),
    value: undefined,
    key: undefined,
    index: undefined,
    finalized: false,
  }

  let valueContent = LHS.trim().replace(stripParensRE, '').trim()
  const trimmedOffset = LHS.indexOf(valueContent)

  const iteratorMatch = valueContent.match(forIteratorRE)
  if (iteratorMatch) {
    valueContent = valueContent.replace(forIteratorRE, '').trim()

    const keyContent = iteratorMatch[1].trim()
    let keyOffset: number | undefined
    if (keyContent) {
      keyOffset = exp.indexOf(keyContent, trimmedOffset + valueContent.length)
      result.key = createAliasExpression(keyContent, keyOffset, true)
    }

    if (iteratorMatch[2]) {
      const indexContent = iteratorMatch[2].trim()

      if (indexContent) {
        result.index = createAliasExpression(
          indexContent,
          exp.indexOf(
            indexContent,
            result.key
              ? keyOffset! + keyContent.length