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Re CLC issue 292 Avoid using partial init and last #263

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Re CLC issue 292 Avoid using partial init and last #263

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18 changes: 14 additions & 4 deletions lib/Data/Format.hs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
{-# LANGUAGE CPP #-}
{-# LANGUAGE Safe #-}

module Data.Format (
Expand Down Expand Up @@ -26,6 +27,9 @@ module Data.Format (

import Control.Monad.Fail
import Data.Char
#if MIN_VERSION_base(4,19,0)
import Data.List (unsnoc)
#endif
import Data.Void
import Text.ParserCombinators.ReadP
import Prelude hiding (fail)
Expand Down Expand Up @@ -227,11 +231,17 @@ zeroPad Nothing s = s
zeroPad (Just i) s = replicate (i - length s) '0' ++ s

trimTrailing :: String -> String
trimTrailing "" = ""
trimTrailing "." = ""
trimTrailing s
| last s == '0' = trimTrailing $ init s
trimTrailing s = s
trimTrailing s = case unsnoc s of
Nothing -> ""
Just (initial, '0') -> trimTrailing initial
_ -> s

#if !MIN_VERSION_base(4,19,0)
unsnoc :: [a] -> Maybe ([a], a)
unsnoc = foldr (\x -> Just . maybe ([], x) (\(~(a, b)) -> (x : a, b))) Nothing
{-# INLINABLE unsnoc #-}
#endif

showNumber :: Show t => SignOption -> Maybe Int -> t -> Maybe String
showNumber signOpt mdigitcount t =
Expand Down
33 changes: 23 additions & 10 deletions test/unix/Test/Format/Format.hs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
{-# LANGUAGE CPP #-}
{-# OPTIONS -fno-warn-orphans #-}

module Test.Format.Format (
Expand All @@ -6,6 +7,9 @@ module Test.Format.Format (

import Data.Char
import Data.Fixed as F
#if MIN_VERSION_base(4,19,0)
import Data.List (unsnoc)
#endif
import Data.Time
import Data.Time.Clock.POSIX
import Foreign
Expand Down Expand Up @@ -151,16 +155,25 @@ unixWorkarounds fmt s
unixWorkarounds _ s = s

compareFormat :: (String -> String) -> String -> TimeZone -> UTCTime -> Result
compareFormat _modUnix fmt zone _time
| last fmt == 'Z' && timeZoneName zone == "" = rejected
compareFormat modUnix fmt zone time =
let
ctime = utcToZonedTime zone time
haskellText = formatTime locale fmt ctime
unixText = unixFormatTime fmt zone time
expectedText = unixWorkarounds fmt (modUnix unixText)
in
assertEqualQC (show time ++ " with " ++ show zone) expectedText haskellText
compareFormat modUnix fmt zone time = case unsnoc fmt of
Nothing ->
error "compareFormat: The impossible happened! Format string is \"\"."
Just (_, lastChar)
| lastChar == 'Z' && timeZoneName zone == "" -> rejected
| otherwise ->
let
ctime = utcToZonedTime zone time
haskellText = formatTime locale fmt ctime
unixText = unixFormatTime fmt zone time
expectedText = unixWorkarounds fmt (modUnix unixText)
in
assertEqualQC (show time ++ " with " ++ show zone) expectedText haskellText

#if !MIN_VERSION_base(4,19,0)
unsnoc :: [a] -> Maybe ([a], a)
unsnoc = foldr (\x -> Just . maybe ([], x) (\(~(a, b)) -> (x : a, b))) Nothing
{-# INLINABLE unsnoc #-}
#endif

-- as found in http://www.opengroup.org/onlinepubs/007908799/xsh/strftime.html
-- plus FgGklz
Expand Down