get tsconfig compiler options

getCompilerOptions.ts

function getCompilerOptions(rootDir: string, configName = 'tsconfig.json') {
  const parseConfigHost: ts.ParseConfigHost = {
    fileExists: ts.sys.fileExists,
    readFile: ts.sys.readFile,
    readDirectory: ts.sys.readDirectory,
    useCaseSensitiveFileNames: true,
  }

  const configFileName = ts.findConfigFile(
    rootDir,
    ts.sys.fileExists,
    configName,
  )

  if (!configFileName) {
    return
  }

  const configFile = ts.readConfigFile(configFileName, ts.sys.readFile)
  const compilerOptions = ts.parseJsonConfigFileContent(
    configFile.config,
    parseConfigHost,
    rootDir,
  )

  return compilerOptions
}