Data.ErrorOr

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 prettyErrAcc, 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.

Documentation

newtype ErrorOr a

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

Monad ErrorOr

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!

Defined in Data.ErrorOr

Methods

(>>=) :: ErrorOr a -> (a -> ErrorOr b) -> ErrorOr b

(>>) :: ErrorOr a -> ErrorOr b -> ErrorOr b

return :: a -> ErrorOr a

Functor ErrorOr

Defined in Data.ErrorOr

Methods

fmap :: (a -> b) -> ErrorOr a -> ErrorOr b

(<$) :: a -> ErrorOr b -> ErrorOr a

MonadFail ErrorOr

Defined in Data.ErrorOr

Methods

fail :: String -> ErrorOr a

Applicative ErrorOr

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

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

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)

MonadError ErrorAcc ErrorOr

Defined in Data.ErrorOr

Methods

throwError :: ErrorAcc -> ErrorOr a

catchError :: ErrorOr a -> (ErrorAcc -> ErrorOr a) -> ErrorOr a

ErrorConv Maybe ErrorOr

Convert from 'Maybe a' to 'ErrorOr a'. It converts Nothing simply to an error with msg Nothing.

Defined in Data.ErrorOr

Methods

toE :: Maybe a -> ErrorOr a

ErrorConv ErrorOr IO

Convert from ErrorOr to IO. toE throws a PrettyErrAcc if the input holds an error.

Defined in Data.ErrorOr

Methods

toE :: ErrorOr a -> IO a

Eq a => Eq (ErrorOr a)

Defined in Data.ErrorOr

Methods

(==) :: ErrorOr a -> ErrorOr a -> Bool

(/=) :: ErrorOr a -> ErrorOr a -> Bool

Ord a => Ord (ErrorOr a)

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)

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)

Defined in Data.ErrorOr

Methods

showsPrec :: Int -> ErrorOr a -> ShowS

show :: ErrorOr a -> String

showList :: [ErrorOr a] -> ShowS

Semigroup a => Semigroup (ErrorOr a)

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)

Defined in Data.ErrorOr

Methods

mempty :: ErrorOr a

mappend :: ErrorOr a -> ErrorOr a -> ErrorOr a

mconcat :: [ErrorOr a] -> ErrorOr a

Show e => ErrorConv (Either e) ErrorOr

Convert from `Either e`, Left becomese error.

Defined in Data.ErrorOr

Methods

toE :: Either e a -> ErrorOr a

tag :: Text -> ErrorOr a -> ErrorOr a

Annotate the error with context information.

pattern Error :: ErrorAcc -> ErrorOr a

pattern OK :: a -> ErrorOr a

isOK :: ErrorOr a -> Bool

isError :: ErrorOr a -> Bool

fromOK :: ErrorOr a -> a

A partial function, like fromRight.

failText :: Text -> ErrorOr a

Produce an error from Text. You can also use fail, which takes a String.

class ErrorConv t s where

Convert between functors that hold error info.

Methods

toE :: t a -> s a

Instances

ErrorConv Maybe ErrorOr

Convert from 'Maybe a' to 'ErrorOr a'. It converts Nothing simply to an error with msg Nothing.

Defined in Data.ErrorOr

Methods

toE :: Maybe a -> ErrorOr a

ErrorConv ErrorOr IO

Convert from ErrorOr to IO. toE throws a PrettyErrAcc if the input holds an error.

Defined in Data.ErrorOr

Methods

toE :: ErrorOr a -> IO a

Show e => ErrorConv (Either e) ErrorOr

Convert from `Either e`, Left becomese error.

Defined in Data.ErrorOr

Methods

toE :: Either e a -> ErrorOr a

data ErrorAcc

Constructors

ErrMessage Text

ErrList (Seq ErrorAcc)

ErrTag Text ErrorAcc

Instances

Eq ErrorAcc

Defined in Data.ErrorOr

Methods

(==) :: ErrorAcc -> ErrorAcc -> Bool

(/=) :: ErrorAcc -> ErrorAcc -> Bool

Ord ErrorAcc

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

Defined in Data.ErrorOr

Methods

readsPrec :: Int -> ReadS ErrorAcc

readList :: ReadS [ErrorAcc]

readPrec :: ReadPrec ErrorAcc

readListPrec :: ReadPrec [ErrorAcc]

Show ErrorAcc

Defined in Data.ErrorOr

Methods

showsPrec :: Int -> ErrorAcc -> ShowS

show :: ErrorAcc -> String

showList :: [ErrorAcc] -> ShowS

IsString ErrorAcc

Defined in Data.ErrorOr

Methods

fromString :: String -> ErrorAcc

Semigroup ErrorAcc

Defined in Data.ErrorOr

Methods

(<>) :: ErrorAcc -> ErrorAcc -> ErrorAcc

sconcat :: NonEmpty ErrorAcc -> ErrorAcc

stimes :: Integral b => b -> ErrorAcc -> ErrorAcc

MonadError ErrorAcc ErrorOr

Defined in Data.ErrorOr

Methods

throwError :: ErrorAcc -> ErrorOr a

catchError :: ErrorOr a -> (ErrorAcc -> ErrorOr a) -> ErrorOr a

prettyErrAcc

Arguments

:: Int

Initial indent, usually 0

-> ErrorAcc

-> Text

Pretty print the error.

newtype PrettyErrAcc

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

Show PrettyErrAcc

Defined in Data.ErrorOr

Methods

showsPrec :: Int -> PrettyErrAcc -> ShowS

show :: PrettyErrAcc -> String

showList :: [PrettyErrAcc] -> ShowS

Exception PrettyErrAcc

Defined in Data.ErrorOr

Methods

toException :: PrettyErrAcc -> SomeException

fromException :: SomeException -> Maybe PrettyErrAcc

displayException :: PrettyErrAcc -> String

tagIO :: Text -> IO a -> IO a

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