module Stack.DefaultColorWhen

( defaultColorWhen

) where

import Stack.Prelude (stdout)

import Stack.Types.Config (ColorWhen (ColorAuto, ColorNever))

import System.Console.ANSI (hSupportsANSIWithoutEmulation)

import System.Environment (lookupEnv)

-- | The default adopts the standard proposed at http://no-color.org/, that

-- color should not be added by default if the @NO_COLOR@ environment variable

-- is present.

defaultColorWhen :: IO ColorWhen

defaultColorWhen = do

-- On Windows, 'hSupportsANSIWithoutEmulation' has the side effect of enabling

-- ANSI for ANSI-capable native (ConHost) terminals, if not already

-- ANSI-enabled. Consequently, it is actioned even if @NO_COLOR@ might exist,

-- as @NO_COLOR@ might be overridden in a yaml configuration file or at the

-- command line.

supportsANSI <- hSupportsANSIWithoutEmulation stdout

mIsNoColor <- lookupEnv "NO_COLOR"

return $ case mIsNoColor of

Just _ -> ColorNever

_ -> case supportsANSI of

Just False -> ColorNever

_ -> ColorAuto