print_stderr False, but stderr is still printed

shelly_test.hs

{-# LANGUAGE OverloadedStrings #-}
{-# OPTIONS_GHC -Wall #-}

module Main where

import System.IO ( Handle )
import System.Environment ( getArgs )
import GHC.IO.Handle ( hIsEOF, hClose, hGetLine )
import Control.Monad.IO.Class ( liftIO )

-- shelly
import Shelly ( runHandle, lastStderr, lastExitCode, errExit, Sh, shelly, print_stdout, print_stderr )

-- text
import qualified Data.Text as T ( pack, unpack )


main :: IO ()
main = do
    args <- getArgs
    (stdout, stderr, exitCode) <- sh $ do
        stdout   <- runHandle "grep" (map T.pack args) (liftIO . stdoutHandler)
        stderr   <- lastStderr
        exitCode <- lastExitCode
        return (stdout, stderr, exitCode)
    putStrLn $ unlines $
        [ "--------------------"
        , unwords ["number of lines in stdout:", show stdout]
        , unwords ["stderr:", T.unpack stderr]
        , unwords ["exitCode:", show exitCode]
        ]

sh :: Sh a -> IO a
sh = shelly . print_stdout False . print_stderr False . errExit False

stdoutHandler :: Handle -> IO Int
stdoutHandler h = do
    eof <- hIsEOF h
    if eof
        then do
            hClose h
            return 0
        else do
            line <- hGetLine h
            putStrLn $ unwords ["STDOUT:", line]
            (1+) <$> stdoutHandler h

to_reproduce.sh

$ echo foo > foo.txt
$ stack runhaskell shelly_test.hs --package shelly --package text -- foo foo.txt
Run from outside a project, using implicit global project config
Using resolver: lts-5.9 from implicit global project's config file: ...
STDOUT: foo
--------------------
number of lines in stdout: 1
stderr:
exitCode: 0

$ stack runhaskell shelly_test.hs --package shelly --package text -- bar foo.txt
Run from outside a project, using implicit global project config
Using resolver: lts-5.9 from implicit global project's config file: ...
--------------------
number of lines in stdout: 0
stderr:
exitCode: 1

$ stack runhaskell shelly_test.hs --package shelly --package text -- foo bar.txt
Run from outside a project, using implicit global project config
Using resolver: lts-5.9 from implicit global project's config file: ...
grep: bar.txt: No such file or directory
--------------------
number of lines in stdout: 0
stderr: grep: bar.txt: No such file or directory

exitCode: 2