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Implement readFile in Terms of withFile for Prompt Closing of Handle #714

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Merged
Bodigrim merged 2 commits into from
Oct 6, 2026
Merged

Implement readFile in Terms of withFile for Prompt Closing of Handle #714

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c837fde
implement `readFile` in terms of `withFile` for prompt closing of handle
julmb Sep 27, 2026
0ef79ee
Add regression test: readFile must close the handle on exception
Lysxia Oct 6, 2026
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5 changes: 2 additions & 3 deletions src/Data/Text/IO.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,8 +45,7 @@ module Data.Text.IO
import Data.Text (Text)
import Prelude hiding (appendFile, getContents, getLine, interact,
putStr, putStrLn, readFile, writeFile)
import System.IO (Handle, IOMode(..), openFile, stdin, stdout,
withFile)
import System.IO (Handle, IOMode(..), stdin, stdout, withFile)
import qualified Control.Exception as E
import Control.Monad (liftM2, when)
import Data.IORef (readIORef)
Expand All @@ -73,7 +72,7 @@ import System.IO.Error (isEOFError)
-- using 'Data.Text.Encoding.decodeUtf8' '.' 'Data.ByteString.readFile'
-- is a much faster and safer alternative.
readFile :: FilePath -> IO Text
readFile name = openFile name ReadMode >>= hGetContents
readFile name = withFile name ReadMode hGetContents

-- | Write a string to a file. The file is truncated to zero length
-- before writing begins.
Expand Down
15 changes: 15 additions & 0 deletions tests/Tests/Regressions.hs
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Expand Up @@ -13,6 +13,7 @@ module Tests.Regressions
import Control.Exception (ErrorCall, SomeException, handle, evaluate, displayException, try)
import Data.Char (isLetter, chr)
import GHC.Exts (Int(..), sizeofByteArray#)
import Control.Exception (IOException)
import System.IO
import System.IO.Temp (withSystemTempFile)
import Test.Tasty.HUnit (assertBool, assertEqual, assertFailure, (@?=))
Expand All @@ -36,6 +37,8 @@ import qualified Test.Tasty as F
import qualified Test.Tasty.HUnit as F
import Tests.Utils (withTempFile)
import System.IO.Error (isFullError)
import Control.Monad (when)
import Data.Either (isRight)

-- Reported by Michael Snoyman: UTF-8 encoding a large lazy bytestring
-- caused either a segfault or attempt to allocate a negative number
Expand Down Expand Up @@ -213,6 +216,17 @@ t648 = withTempFile $ \_ h -> do
line' <- T.hGetLine h
T.append line "\r" @?= line'

t714 :: IO ()
t714 = withTempFile $ \name h -> do
hSetBinaryMode h True
hPutChar h '\xFF'
hClose h
e :: Either IOException T.Text <- try (T.readFile name)
when (isRight e) (assertFailure "should fail")
-- readFile must close the handle even in the case of an exception,
-- in which case the next line should succeed.
openFile name WriteMode >>= hClose

tests :: F.TestTree
tests = F.testGroup "Regressions"
[ F.testCase "hGetContents_crash" hGetContents_crash
Expand All @@ -233,4 +247,5 @@ tests = F.testGroup "Regressions"
, F.testCase "t559" t559
, F.testCase "t633" t633
, F.testCase "t648" t648
, F.testCase "t714" t714
]
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