Best practices: sanitize user input by default, handle unset, and environment variables

#!ek9
defines module site.sanitized.practices

  defines function

    //GOOD: default to sanitized for user input
    processUserData()
      -> input as sanitized String
      <- rtn as String: String(input)

    //Only omit sanitized for trusted internal data
    processInternalData()
      -> trustedInput as String
      <- rtn as String: trustedInput

    doCreateUser()
      -> username as String
      <- created as Boolean: username?

    logValidationError()
      -> message as String
      Stderr().println(message)

    createUser()
      -> username as sanitized String
      <- result as Boolean?

      if username?
        //Safe to process
        result: doCreateUser(username)
      else
        //Threat detected - apply the normal business validation message:
        //defence in depth without leaking what was detected
        result: false
        logValidationError("Invalid username format")

    configurationPath()
      <- rtn as String: String()

      sanitizer <- InputSanitizer(Stderr())
      envVars <- EnvVars()

      //Path traversal patterns are legitimate in environment variables
      configPath <- envVars.get("CONFIG_PATH")
      if configPath?
        rtn: sanitizer.sanitizeWithoutPathChecks(configPath)