cypress/packages/rewriter/lib/js.ts

import * as astTypes from 'ast-types'
import Debug from 'debug'
import { jsRules } from './js-rules'
import * as recast from 'recast'
import * as sourceMaps from './util/source-maps'

const debug = Debug('cypress:rewriter:js')

const defaultPrintOpts: recast.Options = {
  // will only affect reprinted quotes
  quote: 'single',
}

type OriginalSourceInfo = { url: string, js: string }

function _generateDriverError (url: string, err: Error) {
  const args = JSON.stringify({
    errMessage: err.message,
    errStack: err.stack,
    url,
  })

  return `window.top.Cypress.utils.throwErrByPath('proxy.js_rewriting_failed', { args: ${args} })`
}

// a function that, given source info, returns an id that can be used to build the sourcemap later
export type DeferSourceMapRewriteFn = (sourceInfo: OriginalSourceInfo) => string

export function rewriteJsSourceMap (url: string, js: string, inputSourceMap: any): any {
  try {
    const { sourceFileName, sourceMapName, sourceRoot } = sourceMaps.getPaths(url)

    const ast = recast.parse(js, { sourceFileName })

    astTypes.visit(ast, jsRules)

    return recast.print(ast, {
      inputSourceMap,
      sourceMapName,
      sourceRoot,
      ...defaultPrintOpts,
    }).map
  } catch (err) {
    debug('error while parsing JS %o', { err, js: js.slice ? js.slice(0, 500) : js })

    return { err }
  }
}

export function _rewriteJsUnsafe (url: string, js: string, deferSourceMapRewrite?: DeferSourceMapRewriteFn): string {
  const ast = recast.parse(js)

  try {
    astTypes.visit(ast, jsRules)
  } catch (err) {
    // if visiting fails, it points to a bug in our rewriting logic, so raise the error to the driver
    return _generateDriverError(url, err)
  }

  const { code } = recast.print(ast, defaultPrintOpts)

  if (!deferSourceMapRewrite) {
    // no sourcemaps
    return sourceMaps.stripMappingUrl(code)
  }

  // get an ID that can be used to lazy-generate the source map later
  const sourceMapId = deferSourceMapRewrite({ url, js })

  return sourceMaps.urlFormatter(
    // using a relative URL ensures that required cookies + other headers are sent along
    // and can be reused if the user's sourcemap requires an HTTP request to be made
    `/__cypress/source-maps/${sourceMapId}.map`,
    code,
  )
}

export function rewriteJs (url: string, js: string, deferSourceMapRewrite?: DeferSourceMapRewriteFn): string {
  try {
    // rewriting can throw on invalid JS or if there are bugs in the js-rules, so always wrap it
    return _rewriteJsUnsafe(url, js, deferSourceMapRewrite)
  } catch (err) {
    debug('error while parsing JS %o', { err, js: js.slice ? js.slice(0, 500) : js })

    return js
  }
}