@@ -3,38 +3,16 @@
33{-# LANGUAGE OverloadedStrings #-}
44{-# LANGUAGE TemplateHaskell #-}
55{-# LANGUAGE TypeFamilies #-}
6−{-# LANGUAGE UndecidableInstances #-}
76
8−module Control.Monad.Validation
9− ( ValidationT(..)
10− , runValidationT
11− , runValidationTEither
12− , handleValidationT
13− , vError
14− , vWarning
15− , vErrorL
16− , vWarningL
17− , vZoom
18− , vZoomL
19− , mmSingleton
20− , setMempty
21− , neConcat
22− , textErrors
23− , _MonoidMap
24− , MonoidMap(..)
25− ) where
7+module Control.Monad.Validation where
268
27−import Control.Applicative
289import Control.Lens hiding ((.=))
2910import Control.Monad.Base
3011import Control.Monad.Catch
3112import Control.Monad.Except
32−import Control.Monad.Fail
3313import Control.Monad.State.Strict
34−import Control.Monad.Trans.Control
3514import Data.Aeson
3615import Data.Foldable as F
37−import Data.Functor
3816import Data.List as L
3917import Data.Map.Strict as M
4018import Data.Monoid
@@ -42,32 +20,20 @@ import Data.Text as T
4220import Data.Vector as V
4321import Test.QuickCheck
4422
45−
46−-- | Collects all thrown warnings in 'StateT' and errors
47−-- in 'ExceptT' into a single value using 'Monoid'.
23+-- | Collects all throwed "warnings" throwed through StateT and "errors" throwed
24+-- through ExceptT to single value using Monoid
25+-- FIXME: give more instances like HReaderT and MonadBaseControl/MonadMask
4826newtype ValidationT e m a = ValidationT
4927 { unValidationT :: ExceptT e (StateT e m) a
5028 } deriving ( Functor, Applicative, Monad, MonadThrow, MonadCatch
51− , MonadBase b, Alternative, MonadFix, MonadFail, Contravariant
52− , MonadIO, MonadPlus, MonadBaseControl b, MonadMask )
29+ , MonadBase b )
5330
5431instance MonadTrans (ValidationT e) where
5532 lift = ValidationT . lift . lift
5633
5734-- | Map with 'Monoid' instance which 'mappend' its values
58−--
59−-- This can be used as the `e` in `ValidationT e m a` to provide different
60−-- sets of errors and warnings for different keys.
61−--
62−-- >>> :{
63−-- mconcat
64−-- [ MonoidMap $ M.fromList [(1, "foo"), (2, "hello, "), (3, "oh no")]
65−-- , MonoidMap $ M.fromList [(1, "bar"), (2, "world")]
66−-- ]
67−-- :}
68−-- MonoidMap (fromList [(1,"foobar"),(2,"hello, world"),(3,"oh no")])
6935newtype MonoidMap k v = MonoidMap (Map k v)
70− deriving (Eq, Ord, Show, Arbitrary, Foldable)
36+ deriving (Eq, Ord, Show, Arbitrary)
7137
7238makePrisms ''MonoidMap
7339
@@ -95,7 +61,7 @@ instance (ToJSON k, ToJSON v) => ToJSON (MonoidMap k v) where
9561 , "value" .= v ]
9662
9763instance (Ord k, FromJSON k, FromJSON v) => FromJSON (MonoidMap k v) where
98− parseJSON = withArray "MonoidMap" go
64+ parseJSON v = withArray "MonoidMap" go v
9965 where
10066 go arr = do
10167 keyvals <- traverse fromObj arr
@@ -112,60 +78,35 @@ mmAppend :: (Ord k, Monoid v) => MonoidMap k v -> MonoidMap k v -> MonoidMap k v
11278#endif
11379mmAppend (MonoidMap a) (MonoidMap b) = MonoidMap $ M.unionWith (<>) a b
11480
115−-- | Convenient for 'vZoom' as first argument. Will prevent generation
116−-- of map with 'mempty' values.
81+-- | Convenient for 'vZoom' as first artument. Will prevent generation
82+-- of map with 'mempty' values
11783mmSingleton :: (Eq v, Monoid v, Ord k) => k -> v -> MonoidMap k v
118−mmSingleton k v
119− | v == mempty = mempty
120− | otherwise = MonoidMap . M.singleton k $ v
84+mmSingleton k = memptyWrap mempty $ MonoidMap . M.singleton k
12185
122−-- | Sets given value to 'mempty'.
86+-- | Set given value to 'mempty'
12387setMempty :: (Monoid s) => ASetter' s a -> a -> s
12488setMempty setter a = set setter a mempty
12589
126−neConcat :: Foldable f => (a -> a -> a) -> f a -> Maybe a
127−neConcat f a
128− | F.null a = Nothing
129− | otherwise = Just $ F.foldr1 f a
90+memptyWrap :: (Eq a, Monoid a) => b -> (a -> b) -> a -> b
91+memptyWrap b f a
92+ | a == mempty = b
93+ | otherwise = f a
94+
95+-- | If given container is not 'mempty', then use given function to
96+-- append all its elements and return 'Just' result
97+neConcat
98+ :: (Foldable f, Eq (f a), Monoid a, Monoid (f a))
99+ => (a -> a -> a)
100+ -> f a
101+ -> Maybe a
102+neConcat f = memptyWrap Nothing (Just . F.foldl' f mempty)
130103
131−-- | Returns the strings, concatanated with @", "@ if the list is not empty.
132−--
133−-- Returns Nothing if the list is empty
134−--
135−-- >>> textErrors ["foo", "bar"]
136−-- Just "foo, bar"
137−--
138−-- >>> textErrors ["foo"]
139−-- Just "foo"
140−--
141−-- >>> textErrors []
142−-- Nothing
143104textErrors :: [Text] -> Maybe Text
144105textErrors = neConcat (\a b -> a <> ", " <> b)
145106
146−-- | Returns 'mempty' instead of error if no warnings have occured.
147−-- Returns 'Nothing' as the second element of tuple if computation was
148−-- interrupted by 'vError'.
149−--
150−-- Returns all concatenated errors and warnings and the result if no
151−-- errors have occured (warnings could have occured).
152−--
153−-- >>> :{
154−-- runValidationT $ do
155−-- vWarning ["warning1"]
156−-- vError ["error"]
157−-- vWarning ["warning2"]
158−-- return 8
159−-- :}
160−-- (["error","warning1"],Nothing)
161−--
162−-- >>> :{
163−-- runValidationT $ do
164−-- vWarning ["warning1"]
165−-- vWarning ["warning2"]
166−-- return 8
167−-- :}
168−-- (["warning1","warning2"],Just 8)
107+-- | Returns `mempty` instead of error if no warnings was occured. So, your
108+-- error should have `Eq` instance to detect that any error was occured. Returns
109+-- Nothing for second element of tuple if compuration was interruped by 'vError'
169110runValidationT :: (Monoid e, Monad m) => ValidationT e m a -> m (e, Maybe a)
170111runValidationT (ValidationT m) = do
171112 (res, warnings) <- runStateT (runExceptT m) mempty
@@ -173,25 +114,6 @@ runValidationT (ValidationT m) = do
173114 Left err -> (err <> warnings, Nothing)
174115 Right a -> (warnings, Just a)
175116
176−-- | Like 'runValidationT' but doesn't return the result
177−-- if any warning has occured.
178−--
179−-- >>> :{
180−-- runValidationTEither $ do
181−-- vWarning ["warning1"]
182−-- vError ["error"]
183−-- vWarning ["warning2"]
184−-- return 8
185−-- :}
186−-- Left ["error","warning1"]
187−--
188−-- >>> :{
189−-- runValidationTEither $ do
190−-- vWarning ["warning1"]
191−-- vWarning ["warning2"]
192−-- return 8
193−-- :}
194−-- Left ["warning1","warning2"]
195117runValidationTEither
196118 :: (Monoid e, Eq e, Monad m)
197119 => ValidationT e m a
@@ -202,71 +124,28 @@ runValidationTEither action = do
202124 Just a | err == mempty -> Right a
203125 _ -> Left err
204126
205−-- | Like 'runValidationTEither', but takes an error handler instead of
206−-- returning errors and warnings.
207−--
208−-- >>> :{
209−-- handleValidationT (\_ -> return 11) $ do
210−-- vWarning ["warning1"]
211−-- vError ["error"]
212−-- vWarning ["warning2"]
213−-- return 8
214−-- :}
215−-- 11
216−--
217−-- >>> :{
218−-- handleValidationT (\_ -> return 11) $ do
219−-- vWarning ["warning1"]
220−-- vWarning ["warning2"]
221−-- return 8
222−-- :}
223−-- 11
224127handleValidationT
225128 :: (Monoid e, Monad m, Eq e)
226129 => (e -> m a)
227130 -> ValidationT e m a
228131 -> m a
229−handleValidationT handler action =
132+handleValidationT handler action = do
230133 runValidationTEither action >>= either handler return
231134
232−-- | Stops further execution and appends the given error.
135+-- | Stops further execution of validation
233136vError :: (Monad m) => e -> ValidationT e m a
234137vError e = ValidationT $ throwError e
235138
236−-- | Does not stop further execution and appends the given warning.
139+-- | Does not stop further execution, append warning to
237140vWarning :: (Monad m, Monoid e) => e -> ValidationT e m ()
238141vWarning e = ValidationT $ modify' (<> e)
239142
240−-- | Like 'vError' but allows you to use a setter to insert an error somewhere
241−-- deeper into an empty ('mempty') "e" from "ValidationT e m x", which is then
242−-- combined with all gathered warnings.
243143vErrorL :: (Monad m, Monoid e) => ASetter' e a -> a -> ValidationT e m x
244144vErrorL l a = vError $ setMempty l a
245145
246−-- | Like 'vWarning' but allows you to use a setter to insert an error somewhere
247−-- deeper into an empty ('mempty') "e" from "ValidationT e m x", which is then
248−-- combined with all gathered warnings.
249146vWarningL :: (Monad m, Monoid e) => ASetter' e a -> a -> ValidationT e m ()
250147vWarningL l a = vWarning $ setMempty l a
251148
252−-- | Allows you apply a transformation to the "e" in "ValidationT e m x".
253−--
254−-- >>> :{
255−--runValidationT . vZoom (Data.Map.singleton "password errors") $ do
256−-- vWarning ["warning1"]
257−-- vError ["error"]
258−-- vWarning ["warning2"]
259−-- return 8
260−-- :}
261−-- (fromList [("password errors",["error","warning1"])],Nothing)
262−--
263−-- >>> :{
264−-- runValidationT . vZoom (Data.Map.singleton "password errors") $ do
265−-- vWarning ["warning1"]
266−-- vWarning ["warning2"]
267−-- return 8
268−-- :}
269−-- (fromList [("password errors",["warning1","warning2"])],Just 8)
270149vZoom
271150 :: (Monad m, Monoid a, Monoid b)
272151 => (a -> b)
@@ -276,12 +155,11 @@ vZoom up action = do
276155 (err, res) <- lift $ runValidationT action
277156 case res of
278157 Nothing -> vError $ up err
279− Just a -> vWarning (up err) $> a
158+ Just a -> vWarning (up err) *> return a
280159
281−-- | Like 'vZoom' but takes a setter instead of a function.
282160vZoomL
283161 :: (Monad m, Monoid a, Monoid b)
284162 => ASetter' b a
285163 -> ValidationT a m x
286164 -> ValidationT b m x
287−vZoomL l = vZoom (setMempty l)
165+vZoomL l action = vZoom (setMempty l) action