Test.Tasty.Options

Methods

• defaultValue :: v

  The value to use if the option was not supplied explicitly

• parseValue :: String -> Maybe v

  Try to parse an option value from a string. Consider using safeReadBool for boolean options and safeRead for numeric options.

• optionName :: Tagged v String

  The option name. It is used to form the command line option name, for instance. Therefore, it had better not contain spaces or other fancy characters. It is recommended to use dashes instead of spaces.

• optionHelp :: Tagged v String

  The option description or help string. This can be an arbitrary string.

• showDefaultValue :: v -> Maybe String

  How a defaultValue should be displayed in the help string. Nothing (the default implementation) will result in nothing being displayed, while Just def will result in def being advertised as the default in the help string.

• optionCLParser :: Parser v

  A command-line option parser.

  It has a default implementation in terms of the other methods. You may want to override it in some cases (e.g. add a short flag) and flagCLParser, mkFlagCLParser and mkOptionCLParser might come in handy.

  Even if you override this, you still should implement all the methods above, to allow alternative interfaces.

  Do not supply a default value (e.g., with the value function) here for this parser! This is because if no value was provided on the command line we may lookup the option e.g. in the environment. But if the parser always succeeds, we have no way to tell whether the user really provided the option on the command line.

  Similarly, do not use showDefaultWith here, as it will be ignored. Use the showDefaultValue method of IsOption instead.