Evaluate lens only comments the first line of multiline output

[konsumlamm]

Steps to reproduce

Code:

module Lib where

data MultiLine = MultiLine

instance Show MultiLine where
    show MultiLine = "Multi\nLine"

-- >>> MultiLine

Click Evaluate...:

Expected behaviour

Actual behaviour

Versions

GHC: 9.2.2, 9.0.2, 8.10.7
HLS: 1.7.0.0

[xsebek]

Hi @konsumlamm and thanks for the bug report. Indeed we were not prefixing the multi-line show results. 😅

Luckily the fix is a one-liner concatMap lines and I even added a test case for this, though slightly different from yours:

data Multiline = M {l1 :: String, l2 :: String} deriving Read

instance Show Multiline where
  show m = "M {\n  l1=" <> show (l1 m) <> ",\n  l2=" <> show (l2 m) <> "\n}"

-- >>> M "first line" "second line"
-- M {
--   l1="first line",
--   l2="second line"
-- }