Race conditions in testing environmental variables about envy HOT 4 CLOSED

@mookerji are you running the tests concurrently per chance? My QuickCheck tests haven't failed with that kind of error.

from envy.

For something similar I've been recommended "compile with -threaded" though
don't know why.
On Dec 17, 2015 7:50 PM, "Bhaskar Mookerji" [email protected]
wrote:

We found a race condition error while trying to write environmental
unit/property tests. This is likely more of a problem underlying
System.Environment, but I'm wondering if there's a way to deal with it
within Envy. Here's an example definition:

module Types where
import BasicPreludeimport System.Envy
data Conf = Conf
{ _cConfFile :: Maybe String
, cPort :: Maybe Word32
, cTimeout :: Maybe Word32
} deriving ( Eq, Show )
instance FromEnv Conf where
fromEnv =
Conf <$>
envMaybe "CONFFILE" <>
envMaybe "PORT" <>
envMaybe "TIMEOUT"
instance ToEnv Conf where
toEnv Conf{..} =
makeEnv [ "CONFFILE" .= _cConfFile
, "PORT" .= _cPort
, "TIMEOUT" .= _cTimeout
]

and an example test...

module Test
( tests
) where
import BasicPreludeimport Data.Textimport System.Environmentimport System.Envyimport Test.Tastyimport Test.Tasty.HUnit
testEnv :: TestTree
testEnv =
testGroup "Environmental configuration unit test"
[ testCase "Empty configuration" $ do
unsetEnv "SKYLARK_CONFFILE"
unsetEnv "SKYLARK_PORT"
unsetEnv "SKYLARK_TIMEOUT"
c <- decodeEnv :: IO (Either String Conf)
c @?= Right Conf { _cConfFile = Nothing
, _cPort = Nothing
, _cTimeout = Nothing
}
, testCase "Port and Timeout" $ do
unsetEnv "SKYLARK_CONFFILE"
setEnv "SKYLARK_PORT" "1"
setEnv "SKYLARK_TIMEOUT" "1"
c <- decodeEnv :: IO (Either String Conf)
c @?= Right Conf { _cConfFile = Nothing
, _cPort = Just 1
, _cTimeout = Just 1
}
]

This test can sometimes pass, or it fail, with the decoded environment in
one test case being not the one set in that specific test case. For
example, the first case unsetting the environmental variables can instead
read the values set in the second test case. This also appears with a
Quickcheck not too different from the one committed with Envy (
https://gist.github.com/mookerji/d6c9fe48bc35e16bd5690).

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#6.

from envy.

@dmjio Indeed! I thought that I had removed the threaded flags (I know) and had it still fail, but I must have hallucinated. Removing that flag indeed fixed the problem (see: https://github.com/swift-nav/skylark-core/pull/15/files).

That being said, in a more abstract sense, I feel like you'd want still want some notion of thread safety when calling out for environmental variables?

from envy.

@mookerji for setting them, possibly, if what you're doing isn't simple. But that should be up to the user IMO.

from envy.