change-path-reducer-accessing-root-path.js

module.exports = (file, api) => {
  const j = api.jscodeshift
  const rootPathWithDotRegex = /\$\.(\s|$)/g

  const root = j(file.source)

  function detectQuoteStyle (j, root) {
    let detectedQuoting = 'single'

    root
      .find(j.Literal, {
        value: v => typeof v === 'string',
        raw: v => typeof v === 'string'
      })
      .forEach(p => {
        // The raw value is from the original babel source
        if (p.value.raw[0] === "'") {
          detectedQuoting = 'single'
        }

        if (p.value.raw[0] === '"') {
          detectedQuoting = 'double'
        }
      })

    return detectedQuoting
  }

  // transforms a string from '$. | $. | $.' -> '$ | $ | $'
  function transformLiteral (node) {
    const originalValue = node.value.value
    if (rootPathWithDotRegex.test(originalValue)) {
      node.value.value = node.value.value.replace(rootPathWithDotRegex, '$$$1')
    }
  }

  // transforms a template literal from `$. | $. | $.` -> `$ | $ | $`
  function transformTemplateElement (node) {
    const originalValue = node.value.value.raw
    if (rootPathWithDotRegex.test(originalValue)) {
      node.value.value.raw = node.value.value.raw.replace(
        rootPathWithDotRegex,
        '$$$1'
      )
    }
  }

  function refactorReducerMatches (nodeType, transform) {
    root.find(nodeType).forEach(transform)
  }

  refactorReducerMatches(j.Literal, transformLiteral)
  refactorReducerMatches(j.TemplateElement, transformTemplateElement)

  // As Recast is not preserving original quoting, we try to detect it,
  // and default to something sane.
  // See https://github.com/benjamn/recast/issues/171
  // and https://github.com/facebook/jscodeshift/issues/143
  // credit to @skovhus: https://github.com/avajs/ava-codemods/pull/28
  const quote = detectQuoteStyle(j, root)
  return root.toSource({ quote })
}