@@ -3,17 +3,38 @@
33{-# LANGUAGE OverloadedStrings #-}
44{-# LANGUAGE TemplateHaskell #-}
55{-# LANGUAGE TypeFamilies #-}
6+{-# LANGUAGE UndecidableInstances #-}
67
7−module Control.Monad.Validation where
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
826
27+import Control.Applicative
928import Control.Lens hiding ((.=))
1029import Control.Monad.Base
1130import Control.Monad.Catch
1231import Control.Monad.Except
32+import Control.Monad.Fail
1333import Control.Monad.State.Strict
14−import Control.Monad.Trans.Lift.Local
34+import Control.Monad.Trans.Control
1535import Data.Aeson
1636import Data.Foldable as F
37+import Data.Functor
1738import Data.List as L
1839import Data.Map.Strict as M
1940import Data.Monoid
@@ -21,23 +42,32 @@ import Data.Text as T
2142import Data.Vector as V
2243import Test.QuickCheck
2344
24−-- | Collects all throwed "warnings" throwed through StateT and "errors" throwed
25−-- through ExceptT to single value using Monoid
26−-- FIXME: give more instances like HReaderT and MonadBaseControl/MonadMask
45+
46+-- | Collects all thrown warnings in 'StateT' and errors
47+-- in 'ExceptT' into a single value using 'Monoid'.
2748newtype ValidationT e m a = ValidationT
2849 { unValidationT :: ExceptT e (StateT e m) a
2950 } deriving ( Functor, Applicative, Monad, MonadThrow, MonadCatch
30− , MonadBase b )
51+ , MonadBase b, Alternative, MonadFix, MonadFail, Contravariant
52+ , MonadIO, MonadPlus, MonadBaseControl b, MonadMask )
3153
3254instance MonadTrans (ValidationT e) where
3355 lift = ValidationT . lift . lift
3456
35−instance LiftLocal (ValidationT e) where
36− liftLocal _ l f = ValidationT . mapExceptT (mapStateT $ l f) . unValidationT
37−
3857-- | 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")])
3969newtype MonoidMap k v = MonoidMap (Map k v)
40− deriving (Eq, Ord, Show, Arbitrary)
70+ deriving (Eq, Ord, Show, Arbitrary, Foldable)
4171
4272makePrisms ''MonoidMap
4373
@@ -65,7 +95,7 @@ instance (ToJSON k, ToJSON v) => ToJSON (MonoidMap k v) where
6595 , "value" .= v ]
6696
6797instance (Ord k, FromJSON k, FromJSON v) => FromJSON (MonoidMap k v) where
68− parseJSON v = withArray "MonoidMap" go v
98+ parseJSON = withArray "MonoidMap" go
6999 where
70100 go arr = do
71101 keyvals <- traverse fromObj arr
@@ -82,35 +112,60 @@ mmAppend :: (Ord k, Monoid v) => MonoidMap k v -> MonoidMap k v -> MonoidMap k v
82112#endif
83113mmAppend (MonoidMap a) (MonoidMap b) = MonoidMap $ M.unionWith (<>) a b
84114
85−-- | Convenient for 'vZoom' as first artument. Will prevent generation
86−-- of map with 'mempty' values
115+-- | Convenient for 'vZoom' as first argument. Will prevent generation
116+-- of map with 'mempty' values.
87117mmSingleton :: (Eq v, Monoid v, Ord k) => k -> v -> MonoidMap k v
88−mmSingleton k = memptyWrap mempty $ MonoidMap . M.singleton k
118+mmSingleton k v
119+ | v == mempty = mempty
120+ | otherwise = MonoidMap . M.singleton k $ v
89121
90−-- | Set given value to 'mempty'
122+-- | Sets given value to 'mempty'.
91123setMempty :: (Monoid s) => ASetter' s a -> a -> s
92124setMempty setter a = set setter a mempty
93125
94−memptyWrap :: (Eq a, Monoid a) => b -> (a -> b) -> a -> b
95−memptyWrap b f a
96− | a == mempty = b
97− | otherwise = f a
98−
99−-- | If given container is not 'mempty', then use given function to
100−-- append all its elements and return 'Just' result
101−neConcat
102− :: (Foldable f, Eq (f a), Monoid a, Monoid (f a))
103− => (a -> a -> a)
104− -> f a
105− -> Maybe a
106−neConcat f = memptyWrap Nothing (Just . F.foldl' f mempty)
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
107130
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
108143textErrors :: [Text] -> Maybe Text
109144textErrors = neConcat (\a b -> a <> ", " <> b)
110145
111−-- | Returns `mempty` instead of error if no warnings was occured. So, your
112−-- error should have `Eq` instance to detect that any error was occured. Returns
113−-- Nothing for second element of tuple if compuration was interruped by 'vError'
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)
114169runValidationT :: (Monoid e, Monad m) => ValidationT e m a -> m (e, Maybe a)
115170runValidationT (ValidationT m) = do
116171 (res, warnings) <- runStateT (runExceptT m) mempty
@@ -118,6 +173,25 @@ runValidationT (ValidationT m) = do
118173 Left err -> (err <> warnings, Nothing)
119174 Right a -> (warnings, Just a)
120175
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"]
121195runValidationTEither
122196 :: (Monoid e, Eq e, Monad m)
123197 => ValidationT e m a
@@ -128,28 +202,71 @@ runValidationTEither action = do
128202 Just a | err == mempty -> Right a
129203 _ -> Left err
130204
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
131224handleValidationT
132225 :: (Monoid e, Monad m, Eq e)
133226 => (e -> m a)
134227 -> ValidationT e m a
135228 -> m a
136−handleValidationT handler action = do
229+handleValidationT handler action =
137230 runValidationTEither action >>= either handler return
138231
139−-- | Stops further execution of validation
232+-- | Stops further execution and appends the given error.
140233vError :: (Monad m) => e -> ValidationT e m a
141234vError e = ValidationT $ throwError e
142235
143−-- | Does not stop further execution, append warning to
236+-- | Does not stop further execution and appends the given warning.
144237vWarning :: (Monad m, Monoid e) => e -> ValidationT e m ()
145238vWarning e = ValidationT $ modify' (<> e)
146239
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.
147243vErrorL :: (Monad m, Monoid e) => ASetter' e a -> a -> ValidationT e m x
148244vErrorL l a = vError $ setMempty l a
149245
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.
150249vWarningL :: (Monad m, Monoid e) => ASetter' e a -> a -> ValidationT e m ()
151250vWarningL l a = vWarning $ setMempty l a
152251
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)
153270vZoom
154271 :: (Monad m, Monoid a, Monoid b)
155272 => (a -> b)
@@ -159,11 +276,12 @@ vZoom up action = do
159276 (err, res) <- lift $ runValidationT action
160277 case res of
161278 Nothing -> vError $ up err
162− Just a -> vWarning (up err) *> return a
279+ Just a -> vWarning (up err) $> a
163280
281+-- | Like 'vZoom' but takes a setter instead of a function.
164282vZoomL
165283 :: (Monad m, Monoid a, Monoid b)
166284 => ASetter' b a
167285 -> ValidationT a m x
168286 -> ValidationT b m x
169−vZoomL l action = vZoom (setMempty l) action
287+vZoomL l = vZoom (setMempty l)