putStrLn doesn't work correctly with LineBuffering

[domenkozar]

Which can result into

pushing /nix/store/j2yzfcd4wli8lj5i6yvyg6h1sbvjr55i-glibc-2.27
pushing /nix/store/7jgadbmbxp4fz4c96qm154g8sq0y8398-ghc-8.4.3-docpushing /nix/store/vf475f9cg41h8dxz5g8i0mxvbbqpry36-attr-2.4.47

pushing /nix/store/fcyxw5aslw3a82p33x5lhckj0mr6g1s4-bash-4.4-p23

instead of

pushing /nix/store/j2yzfcd4wli8lj5i6yvyg6h1sbvjr55i-glibc-2.27
pushing /nix/store/7jgadbmbxp4fz4c96qm154g8sq0y8398-ghc-8.4.3-doc
pushing /nix/store/vf475f9cg41h8dxz5g8i0mxvbbqpry36-attr-2.4.47
pushing /nix/store/fcyxw5aslw3a82p33x5lhckj0mr6g1s4-bash-4.4-p23

---

It's currently implemented as:

hPutStrLn :: Handle -> Text -> IO ()
hPutStrLn h t = hPutStr h t >> hPutChar h '\n'

The naive approach is to append the newline at the end of t.

GHC's hPutStrLn handles newline as special optimization, I wonder if the same could be implemented for Data.Text.

[Bodigrim]

I don't see an issue here: hPutStrLn does not advertise that it works atomically.