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@Profpatsch
Created November 10, 2022 19:25
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pretty-printing haskell `Show`able types with nicify-lib and hscolour
{-# LANGUAGE LambdaCase #-}
module Pretty
( -- * Pretty printing for error messages
Err,
printPretty,
-- constructors hidden
prettyErrs,
message,
messageString,
pretty,
prettyString,
hscolour',
)
where
import Data.List qualified as List
import Language.Haskell.HsColour
( Output (TTYg),
hscolour,
)
import Language.Haskell.HsColour.ANSI (TerminalType (..))
import Language.Haskell.HsColour.Colourise
( defaultColourPrefs,
)
import PossehlAnalyticsPrelude
import System.Console.ANSI (setSGRCode)
import System.Console.ANSI.Types
( Color (Red),
ColorIntensity (Dull),
ConsoleLayer (Foreground),
SGR (Reset, SetColor),
)
import Text.Nicify (nicify)
-- | Print any 'Show'able type to stderr, formatted nicely and in color. Very helpful for debugging.
printPretty :: Show a => a -> IO ()
printPretty a =
a & pretty & (: []) & prettyErrs & stringToText & putStderrLn
-- | Display a list of 'Err's as a colored error message
-- and abort the test.
prettyErrs :: [Err] -> String
prettyErrs errs = res
where
res = List.intercalate "\n" $ map one errs
one = \case
ErrMsg s -> color Red s
ErrPrettyString s -> prettyShowString s
-- Pretty print a String that was produced by 'show'
prettyShowString :: String -> String
prettyShowString = hscolour' . nicify
-- | Small DSL for pretty-printing errors
data Err
= -- | Message to display in the error
ErrMsg String
| -- | Pretty print a String that was produced by 'show'
ErrPrettyString String
-- | Plain message to display, as 'Text'
message :: Text -> Err
message = ErrMsg . textToString
-- | Plain message to display, as 'String'
messageString :: String -> Err
messageString = ErrMsg
-- | Any 'Show'able to pretty print
pretty :: Show a => a -> Err
pretty x = ErrPrettyString $ show x
-- | Pretty print a String that was produced by 'show'
prettyString :: String -> Err
prettyString s = ErrPrettyString s
-- Prettifying Helpers, mostly stolen from
-- https://hackage.haskell.org/package/hspec-expectations-pretty-diff-0.7.2.5/docs/src/Test.Hspec.Expectations.Pretty.html#prettyColor
hscolour' :: String -> String
hscolour' =
hscolour (TTYg Ansi16Colour) defaultColourPrefs False False "" False
color :: Color -> String -> String
color c s = setSGRCode [SetColor Foreground Dull c] ++ s ++ setSGRCode [Reset]
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