@@ -1,38 +1,77 @@
1+{-# LANGUAGE CPP #-}
2+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
3+{-# LANGUAGE OverloadedStrings #-}
4+{-# LANGUAGE TemplateHaskell #-}
5+{-# LANGUAGE TypeFamilies #-}
6+{-# LANGUAGE UndecidableInstances #-}
17
2−module Common.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+ , vPromote
20+ , mmSingleton
21+ , setMempty
22+ , neConcat
23+ , textErrors
24+ , _MonoidMap
25+ , MonoidMap(..)
26+ ) where
327
28+import Control.Applicative
429import Control.Lens hiding ((.=))
530import Control.Monad.Base
631import Control.Monad.Catch
732import Control.Monad.Except
33+import Control.Monad.Fail
834import Control.Monad.State.Strict
9−import Control.Monad.Trans.Lift.Local
35+import Control.Monad.Trans.Control
1036import Data.Aeson
1137import Data.Foldable as F
38+import Data.Functor
1239import Data.List as L
1340import Data.Map.Strict as M
14−import Data.Monoid
1541import Data.Text as T
1642import Data.Vector as V
1743import Test.QuickCheck
1844
19−-- | Collects all throwed "warnings" throwed through StateT and "errors" throwed
20−-- through ExceptT to single value using Monoid
21−-- FIXME: give more instances like HReaderT and MonadBaseControl/MonadMask
45+#if MIN_VERSION_mtl(2,3,0)
46+import Control.Monad
47+import Control.Monad.Fix
48+#endif
49+
50+-- | Collects all thrown warnings in 'StateT' and errors
51+-- in 'ExceptT' into a single value using 'Monoid'.
2252newtype ValidationT e m a = ValidationT
2353 { unValidationT :: ExceptT e (StateT e m) a
2454 } deriving ( Functor, Applicative, Monad, MonadThrow, MonadCatch
25− , MonadBase b )
55+ , MonadBase b, Alternative, MonadFix, MonadFail, Contravariant
56+ , MonadIO, MonadPlus, MonadBaseControl b, MonadMask )
2657
2758instance MonadTrans (ValidationT e) where
2859 lift = ValidationT . lift . lift
2960
30−instance LiftLocal (ValidationT e) where
31− liftLocal _ l f = ValidationT . mapExceptT (mapStateT $ l f) . unValidationT
32−
3361-- | Map with 'Monoid' instance which 'mappend' its values
62+--
63+-- This can be used as the `e` in `ValidationT e m a` to provide different
64+-- sets of errors and warnings for different keys.
65+--
66+-- >>> :{
67+-- mconcat
68+-- [ MonoidMap $ M.fromList [(1, "foo"), (2, "hello, "), (3, "oh no")]
69+-- , MonoidMap $ M.fromList [(1, "bar"), (2, "world")]
70+-- ]
71+-- :}
72+-- MonoidMap (fromList [(1,"foobar"),(2,"hello, world"),(3,"oh no")])
3473newtype MonoidMap k v = MonoidMap (Map k v)
35− deriving (Eq, Ord, Show, Arbitrary)
74+ deriving (Eq, Ord, Show, Arbitrary, Foldable)
3675
3776makePrisms ''MonoidMap
3877
@@ -43,10 +82,14 @@ instance (Ord k) => Ixed (MonoidMap k v) where
4382instance (Ord k) => At (MonoidMap k v) where
4483 at key = _MonoidMap . at key
4584
85+#if MIN_VERSION_base(4,11,0)
86+instance (Ord k, Semigroup v) => Semigroup (MonoidMap k v) where
87+ (<>) = mmAppend
88+#endif
89+
4690instance (Ord k, Monoid v) => Monoid (MonoidMap k v) where
4791 mempty = MonoidMap M.empty
48− mappend (MonoidMap a) (MonoidMap b) =
49− MonoidMap $ M.unionWith (<>) a b
92+ mappend = (<>)
5093
5194instance (ToJSON k, ToJSON v) => ToJSON (MonoidMap k v) where
5295 toJSON (MonoidMap m) = toJSON $ L.map toObj $ M.toList m
@@ -56,7 +99,7 @@ instance (ToJSON k, ToJSON v) => ToJSON (MonoidMap k v) where
5699 , "value" .= v ]
57100
58101instance (Ord k, FromJSON k, FromJSON v) => FromJSON (MonoidMap k v) where
59− parseJSON v = withArray "MonoidMap" go v
102+ parseJSON = withArray "MonoidMap" go
60103 where
61104 go arr = do
62105 keyvals <- traverse fromObj arr
@@ -66,35 +109,67 @@ instance (Ord k, FromJSON k, FromJSON v) => FromJSON (MonoidMap k v) where
66109 val <- obj .: "value"
67110 return (key, val)
68111
69−-- | Convenient for 'vZoom' as first artument. Will prevent generation
70−-- of map with 'mempty' values
112+#if MIN_VERSION_base(4,11,0)
113+mmAppend :: (Ord k, Semigroup v) => MonoidMap k v -> MonoidMap k v -> MonoidMap k v
114+#else
115+mmAppend :: (Ord k, Monoid v) => MonoidMap k v -> MonoidMap k v -> MonoidMap k v
116+#endif
117+mmAppend (MonoidMap a) (MonoidMap b) = MonoidMap $ M.unionWith (<>) a b
118+
119+-- | Convenient for 'vZoom' as first argument. Will prevent generation
120+-- of map with 'mempty' values.
71121mmSingleton :: (Eq v, Monoid v, Ord k) => k -> v -> MonoidMap k v
72−mmSingleton k = memptyWrap mempty $ MonoidMap . M.singleton k
122+mmSingleton k v
123+ | v == mempty = mempty
124+ | otherwise = MonoidMap . M.singleton k $ v
73125
74−-- | Set given value to 'mempty'
126+-- | Sets given value to 'mempty'.
75127setMempty :: (Monoid s) => ASetter' s a -> a -> s
76128setMempty setter a = set setter a mempty
77129
78−memptyWrap :: (Eq a, Monoid a) => b -> (a -> b) -> a -> b
79−memptyWrap b f a
80− | a == mempty = b
81− | otherwise = f a
82−
83−-- | If given container is not 'mempty', then use given function to
84−-- append all its elements and return 'Just' result
85−neConcat
86− :: (Foldable f, Eq (f a), Monoid a, Monoid (f a))
87− => (a -> a -> a)
88− -> f a
89− -> Maybe a
90−neConcat f = memptyWrap Nothing (Just . F.foldl' f mempty)
130+neConcat :: Foldable f => (a -> a -> a) -> f a -> Maybe a
131+neConcat f a
132+ | F.null a = Nothing
133+ | otherwise = Just $ F.foldr1 f a
91134
135+-- | Returns the strings, concatanated with @", "@ if the list is not empty.
136+--
137+-- Returns Nothing if the list is empty
138+--
139+-- >>> textErrors ["foo", "bar"]
140+-- Just "foo, bar"
141+--
142+-- >>> textErrors ["foo"]
143+-- Just "foo"
144+--
145+-- >>> textErrors []
146+-- Nothing
92147textErrors :: [Text] -> Maybe Text
93148textErrors = neConcat (\a b -> a <> ", " <> b)
94149
95−-- | Returns `mempty` instead of error if no warnings was occured. So, your
96−-- error should have `Eq` instance to detect that any error was occured. Returns
97−-- Nothing for second element of tuple if compuration was interruped by 'vError'
150+-- | Returns 'mempty' instead of error if no warnings have occurred.
151+-- Returns 'Nothing' as the second element of tuple if computation was
152+-- interrupted by 'vError'.
153+--
154+-- Returns all concatenated errors and warnings and the result if no
155+-- errors have occurred (warnings could have occurred).
156+--
157+-- >>> :{
158+-- runValidationT $ do
159+-- vWarning ["warning1"]
160+-- vError ["error"]
161+-- vWarning ["warning2"]
162+-- return 8
163+-- :}
164+-- (["error","warning1"],Nothing)
165+--
166+-- >>> :{
167+-- runValidationT $ do
168+-- vWarning ["warning1"]
169+-- vWarning ["warning2"]
170+-- return 8
171+-- :}
172+-- (["warning1","warning2"],Just 8)
98173runValidationT :: (Monoid e, Monad m) => ValidationT e m a -> m (e, Maybe a)
99174runValidationT (ValidationT m) = do
100175 (res, warnings) <- runStateT (runExceptT m) mempty
@@ -102,6 +177,25 @@ runValidationT (ValidationT m) = do
102177 Left err -> (err <> warnings, Nothing)
103178 Right a -> (warnings, Just a)
104179
180+-- | Like 'runValidationT' but doesn't return the result
181+-- if any warning has occurred.
182+--
183+-- >>> :{
184+-- runValidationTEither $ do
185+-- vWarning ["warning1"]
186+-- vError ["error"]
187+-- vWarning ["warning2"]
188+-- return 8
189+-- :}
190+-- Left ["error","warning1"]
191+--
192+-- >>> :{
193+-- runValidationTEither $ do
194+-- vWarning ["warning1"]
195+-- vWarning ["warning2"]
196+-- return 8
197+-- :}
198+-- Left ["warning1","warning2"]
105199runValidationTEither
106200 :: (Monoid e, Eq e, Monad m)
107201 => ValidationT e m a
@@ -112,28 +206,71 @@ runValidationTEither action = do
112206 Just a | err == mempty -> Right a
113207 _ -> Left err
114208
209+-- | Like 'runValidationTEither', but takes an error handler instead of
210+-- returning errors and warnings.
211+--
212+-- >>> :{
213+-- handleValidationT (\_ -> return 11) $ do
214+-- vWarning ["warning1"]
215+-- vError ["error"]
216+-- vWarning ["warning2"]
217+-- return 8
218+-- :}
219+-- 11
220+--
221+-- >>> :{
222+-- handleValidationT (\_ -> return 11) $ do
223+-- vWarning ["warning1"]
224+-- vWarning ["warning2"]
225+-- return 8
226+-- :}
227+-- 11
115228handleValidationT
116229 :: (Monoid e, Monad m, Eq e)
117230 => (e -> m a)
118231 -> ValidationT e m a
119232 -> m a
120−handleValidationT handler action = do
233+handleValidationT handler action =
121234 runValidationTEither action >>= either handler return
122235
123−-- | Stops further execution of validation
236+-- | Stops further execution and appends the given error.
124237vError :: (Monad m) => e -> ValidationT e m a
125238vError e = ValidationT $ throwError e
126239
127−-- | Does not stop further execution, append warning to
240+-- | Does not stop further execution and appends the given warning.
128241vWarning :: (Monad m, Monoid e) => e -> ValidationT e m ()
129242vWarning e = ValidationT $ modify' (<> e)
130243
244+-- | Like 'vError' but allows you to use a setter to insert an error somewhere
245+-- deeper into an empty ('mempty') "e" from "ValidationT e m x", which is then
246+-- combined with all gathered warnings.
131247vErrorL :: (Monad m, Monoid e) => ASetter' e a -> a -> ValidationT e m x
132248vErrorL l a = vError $ setMempty l a
133249
250+-- | Like 'vWarning' but allows you to use a setter to insert an error somewhere
251+-- deeper into an empty ('mempty') "e" from "ValidationT e m x", which is then
252+-- combined with all gathered warnings.
134253vWarningL :: (Monad m, Monoid e) => ASetter' e a -> a -> ValidationT e m ()
135254vWarningL l a = vWarning $ setMempty l a
136255
256+-- | Allows you apply a transformation to the "e" in "ValidationT e m x".
257+--
258+-- >>> :{
259+--runValidationT . vZoom (Data.Map.singleton "password errors") $ do
260+-- vWarning ["warning1"]
261+-- vError ["error"]
262+-- vWarning ["warning2"]
263+-- return 8
264+-- :}
265+-- (fromList [("password errors",["error","warning1"])],Nothing)
266+--
267+-- >>> :{
268+-- runValidationT . vZoom (Data.Map.singleton "password errors") $ do
269+-- vWarning ["warning1"]
270+-- vWarning ["warning2"]
271+-- return 8
272+-- :}
273+-- (fromList [("password errors",["warning1","warning2"])],Just 8)
137274vZoom
138275 :: (Monad m, Monoid a, Monoid b)
139276 => (a -> b)
@@ -143,11 +280,21 @@ vZoom up action = do
143280 (err, res) <- lift $ runValidationT action
144281 case res of
145282 Nothing -> vError $ up err
146− Just a -> vWarning (up err) *> return a
283+ Just a -> vWarning (up err) $> a
147284
285+-- | Like 'vZoom' but takes a setter instead of a function.
148286vZoomL
149287 :: (Monad m, Monoid a, Monoid b)
150288 => ASetter' b a
151289 -> ValidationT a m x
152290 -> ValidationT b m x
153−vZoomL l action = vZoom (setMempty l) action
291+vZoomL l = vZoom (setMempty l)
292+
293+-- | Turn any warnings the have occurred into errors.
294+vPromote
295+ :: (Monad m, Monoid a, Eq a)
296+ => ValidationT a m x
297+ -> ValidationT a m x
298+vPromote m = do
299+ err <- lift $ runValidationTEither m
300+ either vError return err