Stop using partial functions

[NorfairKing]

As of GHC 9.10 I get this exception in cron:

smos-scheduler        >     test/Smos/Scheduler/RecurrenceSpec.hs:18
smos-scheduler        >   ✗ 1 Smos.Scheduler.RecurrenceSpec.computeNextRun.always activates a new item
smos-scheduler        >       Retries: 3 (does not look flaky)
smos-scheduler        >       Failed after 15 tests and 5 shrinks
smos-scheduler        >       Generated: 1858-11-17 00:00:00
smos-scheduler        >       Generated: PropertyValue {propertyValueText = ""}
smos-scheduler        >       Generated: ScheduleItem {scheduleItemDescription = Nothing, scheduleItemTemplateFile = "", scheduleItemDestination = DestinationPathTemplate {destinationPathTemplatePath = "a"}, scheduleItemRecurrence = RentRecurrence CronSchedule * 1-0 * * *}
smos-scheduler        >       NonEmpty.fromList: empty list
smos-scheduler        >       CallStack (from HasCallStack):
smos-scheduler        >         error, called at libraries/base/src/Data/List/NonEmpty.hs:238:15 in base:Data.List.NonEmpty
smos-scheduler        >         fromList, called at src/System/Cron/Internal/Check.hs:168:40 in cron-0.7.2-JSDGoxugtX53Eyo8zZdziC:System.Cron.Internal.Check
smos-scheduler        >       HasCallStack backtrace:
smos-scheduler        >         collectBacktraces, called at libraries/ghc-internal/src/GHC/Internal/Exception.hs:169:13 in ghc-internal:GHC.Internal.Exception
smos-scheduler        >         toExceptionWithBacktrace, called at libraries/ghc-internal/src/GHC/Internal/Exception.hs:204:5 in ghc-internal:GHC.Internal.Exception
smos-scheduler        >         error, called at libraries/base/src/Data/List/NonEmpty.hs:238:15 in base:Data.List.NonEmpty
smos-scheduler        >         fromList, called at src/System/Cron/Internal/Check.hs:168:40 in cron-0.7.2-JSDGoxugtX53Eyo8zZdziC:System.Cron.Internal.Check

[NorfairKing]

It looks like the root of the bug is that the range field is not validated in validBF:

[validBF](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#validBF)
    :: [BaseField](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#BaseField)
    -> Int
    -- ^ Min value
    -> Int
    -- ^ Max value
    -> Bool
[validBF](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#validBF) [Star](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#Star) _ _ = True
[validBF](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#validBF) ([SpecificField'](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#SpecificField%27) ([SpecificField](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#SpecificField) [n](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080083))) [mn](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080084) [mx](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080085) =
  inRange ([mn](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080084), [mx](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080085)) [n](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080083)
[validBF](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#validBF) ([RangeField'](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#RangeField%27) ([RangeField](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#RangeField) [n1](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080088) [n2](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080089))) [mn](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080090) [mx](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080091) =
  inRange ([mn](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080090), [mx](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080091)) [n1](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080088) && inRange ([mn](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080090), [mx](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080091)) [n2](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080089)

No mention of:

[mkRangeField](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#mkRangeField) :: Int -> Int -> Maybe [RangeField](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#RangeField)
[mkRangeField](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#mkRangeField) [x](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080351) [y](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080352)
  | [x](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080351) <= [y](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080352)    = Just ([RangeField](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#RangeField) [x](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080351) [y](https://hackage.haskell.org/package/cron-0.7.2/docs/src/System.Cron.Types.html#local-6989586621679080352))
  | otherwise = Nothing

I can recommend using hackage.haskell.org/package/validity for validation.

EDIT: oh bloody hell you can't copy code from Hackage anymore?

[NorfairKing]

What I don't understand is why this didn't happen before 🤔