Add flag for --no-colors

README.md

@@ -221,10 +221,11 @@ niv - dependency manager for Nix projects
 
 version: 0.2.18
 
-Usage: niv [-s|--sources-file FILE] COMMAND
+Usage: niv [-s|--sources-file FILE] [--no-colors] COMMAND
 
 Available options:
   -s,--sources-file FILE   Use FILE instead of nix/sources.json
+  --no-colors              Don't use colors in output
   -h,--help                Show this help text
   --version                Print version
 

src/Niv/Cli.hs

@@ -54,16 +54,17 @@ li = liftIO
 cli :: IO ()
 cli = do
   warnGitHubEnvVars
-  (fsj, nio) <-
+  ((fsj, colors), nio) <-
     execParserPure' Opts.defaultPrefs opts <$> getArgs
       >>= Opts.handleParseResult
+  setColors colors
   runReaderT (runNIO nio) fsj
   where
     execParserPure' pprefs pinfo [] =
       Opts.Failure $
         Opts.parserFailure pprefs pinfo Opts.ShowHelpText mempty
     execParserPure' pprefs pinfo args = Opts.execParserPure pprefs pinfo args
-    opts = Opts.info ((,) <$> parseFindSourcesJson <*> (parseCommand <**> Opts.helper <**> versionflag)) $ mconcat desc
+    opts = Opts.info ((,) <$> ((,) <$> parseFindSourcesJson <*> parseColors) <*> (parseCommand <**> Opts.helper <**> versionflag)) $ mconcat desc
     desc =
       [ Opts.fullDesc,
         Opts.headerDoc $ Just $
@@ -80,6 +81,12 @@ cli = do
               <> Opts.help "Use FILE instead of nix/sources.json"
           )
         <|> pure Auto
+    parseColors =
+      (\case True -> Never; False -> Always)
+        <$> Opts.switch
+          ( Opts.long "no-colors"
+              <> Opts.help "Don't use colors in output"
+          )
     versionflag :: Opts.Parser (a -> a)
     versionflag =
       Opts.abortOption (Opts.InfoMsg (showVersion version)) $

src/Niv/Logger.hs

@@ -4,7 +4,9 @@
 {-# LANGUAGE OverloadedStrings #-}
 
 module Niv.Logger
-  ( job,
+  ( Colors (Always, Never),
+    job,
+    setColors,
     bug,
     tsay,
     say,
@@ -35,6 +37,27 @@ import System.Exit (exitFailure)
 import System.IO.Unsafe (unsafePerformIO)
 import UnliftIO
 
+-- A somewhat hacky way of deciding whether or not to use SGR codes, by writing
+-- and reading a global variable unsafely.
+-- This should be fine as long as the IORef is written right after argument
+-- parsing, and as long as the value is never changed.
+-- NOTE: this won't work in GHCi.
+
+data Colors
+  = Always
+  | Never
+  deriving (Eq)
+
+colors :: IORef Colors
+colors = unsafePerformIO $ newIORef Always
+{-# NOINLINE colors #-}
+
+setColors :: Colors -> IO ()
+setColors = writeIORef colors
+
+useColors :: Bool
+useColors = unsafePerformIO $ (\c -> c == Always) <$> readIORef colors
+
 type S = String -> String
 
 type T = T.Text -> T.Text
@@ -85,61 +108,58 @@ twarn = tsay . mkWarn
 mkNote :: T.Text -> T.Text
 mkNote w = tbold (tblue "NOTE") <> ": " <> w
 
+color :: ANSI.Color -> String -> String
+color c str =
+  if useColors
+    then
+      ANSI.setSGRCode [ANSI.SetConsoleIntensity ANSI.BoldIntensity]
+        <> ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Vivid c]
+        <> str
+        <> ANSI.setSGRCode [ANSI.Reset]
+    else str
+
+colorFaint :: ANSI.Color -> String -> String
+colorFaint c str =
+  if useColors
+    then
+      ANSI.setSGRCode [ANSI.SetConsoleIntensity ANSI.FaintIntensity]
+        <> ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Vivid c]
+        <> str
+        <> ANSI.setSGRCode [ANSI.Reset]
+    else str
+
 green :: S
-green str =
-  ANSI.setSGRCode [ANSI.SetConsoleIntensity ANSI.BoldIntensity]
-    <> ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Vivid ANSI.Green]
-    <> str
-    <> ANSI.setSGRCode [ANSI.Reset]
+green = color ANSI.Green
 
 tgreen :: T
 tgreen = t green
 
 yellow :: S
-yellow str =
-  ANSI.setSGRCode [ANSI.SetConsoleIntensity ANSI.BoldIntensity]
-    <> ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Vivid ANSI.Yellow]
-    <> str
-    <> ANSI.setSGRCode [ANSI.Reset]
+yellow = color ANSI.Yellow
 
 tyellow :: T
 tyellow = t yellow
 
 blue :: S
-blue str =
-  ANSI.setSGRCode [ANSI.SetConsoleIntensity ANSI.BoldIntensity]
-    <> ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Vivid ANSI.Blue]
-    <> str
-    <> ANSI.setSGRCode [ANSI.Reset]
+blue = color ANSI.Blue
 
 tblue :: T
 tblue = t blue
 
 red :: S
-red str =
-  ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Vivid ANSI.Red]
-    <> str
-    <> ANSI.setSGRCode [ANSI.Reset]
+red = color ANSI.Red
 
 tred :: T
 tred = t red
 
 bold :: S
-bold str =
-  ANSI.setSGRCode [ANSI.SetConsoleIntensity ANSI.BoldIntensity]
-    <> ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Vivid ANSI.White]
-    <> str
-    <> ANSI.setSGRCode [ANSI.Reset]
+bold = color ANSI.White
 
 tbold :: T
 tbold = t bold
 
 faint :: String -> String
-faint str =
-  ANSI.setSGRCode [ANSI.SetConsoleIntensity ANSI.FaintIntensity]
-    <> ANSI.setSGRCode [ANSI.SetColor ANSI.Foreground ANSI.Vivid ANSI.White]
-    <> str
-    <> ANSI.setSGRCode [ANSI.Reset]
+faint = colorFaint ANSI.White
 
 tfaint :: T
 tfaint = t faint