Safe Haskell	None
Language	Haskell2010

Data.ErrorOr

Description

Provides composable and hierarchical errors, with pretty printing. The errors are accumulated in a tree like structure, ErrorAcc. ErrorAcc is disigned to be read by humans, via pretty, not dispatched on by code. Using toE to convert an ErrorOr to IO throws (in case it holds an error) a PrettyErrAcc that uses pretty in the show instance.

Synopsis

newtype ErrorOr a = ErrorOr {
- errorOrToEither :: Either ErrorAcc a
}
err :: Text -> ErrorOr a
tag :: Text -> ErrorOr a -> ErrorOr a
pattern Error :: ErrorAcc -> ErrorOr a
pattern OK :: a -> ErrorOr a
isOK :: ErrorOr a -> Bool
isError :: ErrorOr a -> Bool
fromOK :: ErrorOr a -> a
class ErrorConv t s where
- toE :: t a -> s a
data ErrorAcc
- = Message Text
- | List (Seq ErrorAcc)
- | Tag Text ErrorAcc
pretty :: Int -> ErrorAcc -> Text
newtype PrettyErrAcc = PrettyErrAcc {
- unPrettyErrAcc :: ErrorAcc
}
tagIO :: Text -> IO a -> IO a

Documentation

newtype ErrorOr a Source #

Use Applicative's sequenceA and sequenceA_ to compose ErrorOrs as opposed to Monad derived functions like sequence.

Constructors

ErrorOr
Fields errorOrToEither :: Either ErrorAcc a

Instances

Instances details

Monad ErrorOr Source #	OrError's instances for `Monad` and `Applicative` don't align, but the `Monad` and `MonadFail` instances are too useful (as in convenient) to pass on. In particular, composing two failing actions using the `Applicative` instance creates a composite error, where as composing the same two actions using the `Monad` instance `(>>)` produces only the error from the first action in the sequence. This is a consequence of the fact that for Monads executing the second of two actions (`(>>)` is defined in terms of `(>>=)`) requires the result from the first to be passed to the second: the very result that is not available if the first action fails!
Instance details Defined in Data.ErrorOr Methods (>>=) :: ErrorOr a -> (a -> ErrorOr b) -> ErrorOr b # (>>) :: ErrorOr a -> ErrorOr b -> ErrorOr b # return :: a -> ErrorOr a #
Functor ErrorOr Source #
Instance details Defined in Data.ErrorOr Methods fmap :: (a -> b) -> ErrorOr a -> ErrorOr b # (<$) :: a -> ErrorOr b -> ErrorOr a #
MonadFail ErrorOr Source #
Instance details Defined in Data.ErrorOr Methods fail :: String -> ErrorOr a #
Applicative ErrorOr Source #
Instance details Defined in Data.ErrorOr Methods pure :: a -> ErrorOr a # (<>) :: ErrorOr (a -> b) -> ErrorOr a -> ErrorOr b # liftA2 :: (a -> b -> c) -> ErrorOr a -> ErrorOr b -> ErrorOr c # (>) :: ErrorOr a -> ErrorOr b -> ErrorOr b # (<*) :: ErrorOr a -> ErrorOr b -> ErrorOr a #
Foldable ErrorOr Source #
Instance details Defined in Data.ErrorOr Methods fold :: Monoid m => ErrorOr m -> m # foldMap :: Monoid m => (a -> m) -> ErrorOr a -> m # foldMap' :: Monoid m => (a -> m) -> ErrorOr a -> m # foldr :: (a -> b -> b) -> b -> ErrorOr a -> b # foldr' :: (a -> b -> b) -> b -> ErrorOr a -> b # foldl :: (b -> a -> b) -> b -> ErrorOr a -> b # foldl' :: (b -> a -> b) -> b -> ErrorOr a -> b # foldr1 :: (a -> a -> a) -> ErrorOr a -> a # foldl1 :: (a -> a -> a) -> ErrorOr a -> a # toList :: ErrorOr a -> [a] # null :: ErrorOr a -> Bool # length :: ErrorOr a -> Int # elem :: Eq a => a -> ErrorOr a -> Bool # maximum :: Ord a => ErrorOr a -> a # minimum :: Ord a => ErrorOr a -> a # sum :: Num a => ErrorOr a -> a # product :: Num a => ErrorOr a -> a #
Traversable ErrorOr Source #
Instance details Defined in Data.ErrorOr Methods traverse :: Applicative f => (a -> f b) -> ErrorOr a -> f (ErrorOr b) # sequenceA :: Applicative f => ErrorOr (f a) -> f (ErrorOr a) # mapM :: Monad m => (a -> m b) -> ErrorOr a -> m (ErrorOr b) # sequence :: Monad m => ErrorOr (m a) -> m (ErrorOr a) #
ErrorConv Maybe ErrorOr Source #	Convert from 'Maybe a' to 'ErrorOr a'. It converts `Nothing` simply to an error with msg Nothing.
Instance details Defined in Data.ErrorOr Methods toE :: Maybe a -> ErrorOr a Source #
ErrorConv ErrorOr IO Source #	Convert from ErrorOr to IO. `toE` throws a `PrettyErrAcc` if the input holds an error.
Instance details Defined in Data.ErrorOr Methods toE :: ErrorOr a -> IO a Source #
Eq a => Eq (ErrorOr a) Source #
Instance details Defined in Data.ErrorOr Methods (==) :: ErrorOr a -> ErrorOr a -> Bool # (/=) :: ErrorOr a -> ErrorOr a -> Bool #
Ord a => Ord (ErrorOr a) Source #
Instance details Defined in Data.ErrorOr Methods compare :: ErrorOr a -> ErrorOr a -> Ordering # (<) :: ErrorOr a -> ErrorOr a -> Bool # (<=) :: ErrorOr a -> ErrorOr a -> Bool # (>) :: ErrorOr a -> ErrorOr a -> Bool # (>=) :: ErrorOr a -> ErrorOr a -> Bool # max :: ErrorOr a -> ErrorOr a -> ErrorOr a # min :: ErrorOr a -> ErrorOr a -> ErrorOr a #
Read a => Read (ErrorOr a) Source #
Instance details Defined in Data.ErrorOr Methods readsPrec :: Int -> ReadS (ErrorOr a) # readList :: ReadS [ErrorOr a] # readPrec :: ReadPrec (ErrorOr a) # readListPrec :: ReadPrec [ErrorOr a] #
Show a => Show (ErrorOr a) Source #
Instance details Defined in Data.ErrorOr Methods showsPrec :: Int -> ErrorOr a -> ShowS # show :: ErrorOr a -> String # showList :: [ErrorOr a] -> ShowS #
Semigroup a => Semigroup (ErrorOr a) Source #
Instance details Defined in Data.ErrorOr Methods (<>) :: ErrorOr a -> ErrorOr a -> ErrorOr a # sconcat :: NonEmpty (ErrorOr a) -> ErrorOr a # stimes :: Integral b => b -> ErrorOr a -> ErrorOr a #
(Semigroup (ErrorOr a), Monoid a) => Monoid (ErrorOr a) Source #
Instance details Defined in Data.ErrorOr Methods mempty :: ErrorOr a # mappend :: ErrorOr a -> ErrorOr a -> ErrorOr a # mconcat :: [ErrorOr a] -> ErrorOr a #

err :: Text -> ErrorOr a Source #

Produce an error.

tag :: Text -> ErrorOr a -> ErrorOr a Source #

Annotate the error with context information.

pattern Error :: ErrorAcc -> ErrorOr a Source #

pattern OK :: a -> ErrorOr a Source #

isOK :: ErrorOr a -> Bool Source #

isError :: ErrorOr a -> Bool Source #

fromOK :: ErrorOr a -> a Source #

A partial function, like fromRight.

class ErrorConv t s where Source #

Convert between functors that hold error info.

Methods

toE :: t a -> s a Source #

Instances

Instances details

ErrorConv Maybe ErrorOr Source #	Convert from 'Maybe a' to 'ErrorOr a'. It converts `Nothing` simply to an error with msg Nothing.
Instance details Defined in Data.ErrorOr Methods toE :: Maybe a -> ErrorOr a Source #
ErrorConv ErrorOr IO Source #	Convert from ErrorOr to IO. `toE` throws a `PrettyErrAcc` if the input holds an error.
Instance details Defined in Data.ErrorOr Methods toE :: ErrorOr a -> IO a Source #

data ErrorAcc Source #

Constructors

Message Text
List (Seq ErrorAcc)
Tag Text ErrorAcc

Instances

Instances details

Eq ErrorAcc Source #
Instance details Defined in Data.ErrorOr Methods (==) :: ErrorAcc -> ErrorAcc -> Bool # (/=) :: ErrorAcc -> ErrorAcc -> Bool #
Ord ErrorAcc Source #
Instance details Defined in Data.ErrorOr Methods compare :: ErrorAcc -> ErrorAcc -> Ordering # (<) :: ErrorAcc -> ErrorAcc -> Bool # (<=) :: ErrorAcc -> ErrorAcc -> Bool # (>) :: ErrorAcc -> ErrorAcc -> Bool # (>=) :: ErrorAcc -> ErrorAcc -> Bool # max :: ErrorAcc -> ErrorAcc -> ErrorAcc # min :: ErrorAcc -> ErrorAcc -> ErrorAcc #
Read ErrorAcc Source #
Instance details Defined in Data.ErrorOr Methods readsPrec :: Int -> ReadS ErrorAcc # readList :: ReadS [ErrorAcc] # readPrec :: ReadPrec ErrorAcc # readListPrec :: ReadPrec [ErrorAcc] #
Show ErrorAcc Source #
Instance details Defined in Data.ErrorOr Methods showsPrec :: Int -> ErrorAcc -> ShowS # show :: ErrorAcc -> String # showList :: [ErrorAcc] -> ShowS #
Semigroup ErrorAcc Source #
Instance details Defined in Data.ErrorOr Methods (<>) :: ErrorAcc -> ErrorAcc -> ErrorAcc # sconcat :: NonEmpty ErrorAcc -> ErrorAcc # stimes :: Integral b => b -> ErrorAcc -> ErrorAcc #

pretty Source #

Arguments

:: Int	Initial indent, usually 0
-> ErrorAcc
-> Text

Pretty print the error.

newtype PrettyErrAcc Source #

A wrapper over ErrorAcc to provide human readable exceptions. (Exception class' displayException does not seem to be used by GHC) https://stackoverflow.com/questions/55490766/why-doesn-t-ghc-use-my-displayexception-method

Constructors

PrettyErrAcc
Fields unPrettyErrAcc :: ErrorAcc

Instances

Instances details

Show PrettyErrAcc Source #
Instance details Defined in Data.ErrorOr Methods showsPrec :: Int -> PrettyErrAcc -> ShowS # show :: PrettyErrAcc -> String # showList :: [PrettyErrAcc] -> ShowS #
Exception PrettyErrAcc Source #
Instance details Defined in Data.ErrorOr Methods toException :: PrettyErrAcc -> SomeException # fromException :: SomeException -> Maybe PrettyErrAcc # displayException :: PrettyErrAcc -> String #

tagIO :: Text -> IO a -> IO a Source #

Tag an exception with an annotation.

It acts on two types of exceptions: IOException and PrettyErrAcc. For PrettyErrAcc it is streightforward tagging. For IOException, otoh, it converts the error message into Text via String and turns it into PrettyErrAcc tagged with provided adnotation.

This is rather a convenience function. Sometimes it is convenient to fail "msg" in IO, and tag it higher up with some context. The need for tagIO often comes with lookup (from error-or-utils package) when used from IO, which is overloaded for MonadFail.

Since ver 0.1.1.0