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diff --git a/users/Profpatsch/my-prelude/Pretty.hs b/users/Profpatsch/my-prelude/Pretty.hs
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+{-# LANGUAGE ImportQualifiedPost #-}
+{-# 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 Data.Text qualified as Text
+import Language.Haskell.HsColour
+  ( Output (TTYg),
+    hscolour,
+  )
+import Language.Haskell.HsColour.ANSI (TerminalType (..))
+import Language.Haskell.HsColour.Colourise
+  ( defaultColourPrefs,
+  )
+import MyPrelude
+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 . Text.unpack
+
+-- | 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]