@@ -1,3 +1,4 @@
1+{-# LANGUAGE ConstraintKinds #-}
12{-# LANGUAGE CPP #-}
23{-# LANGUAGE DataKinds #-}
34{-# LANGUAGE DefaultSignatures #-}
@@ -13,56 +14,54 @@
1314{-# LANGUAGE TypeFamilies #-}
1415{-# LANGUAGE TypeOperators #-}
1516{-# LANGUAGE UndecidableInstances #-}
17+#include "overlapping-compat.h"
1618module Web.Internal.FormUrlEncoded where
1719
18−#if __GLASGOW_HASKELL__ < 710
19−import Control.Applicative
20−import Data.Traversable
21−#endif
22−
23−#if __GLASGOW_HASKELL__ < 800
24−import GHC.Exts (IsList (..))
25−#else
26−import GHC.Exts (IsList (..), Constraint)
27−import GHC.TypeLits
28−#endif
20+import Prelude ()
21+import Prelude.Compat
2922
23+import Control.Applicative (Const(Const))
3024import Control.Arrow ((***))
3125import Control.Monad ((<=<))
32−import Data.ByteString.Builder (toLazyByteString, shortByteString)
26+import Data.ByteString.Builder (shortByteString, toLazyByteString)
3327import qualified Data.ByteString.Lazy as BSL
3428import qualified Data.ByteString.Lazy.Char8 as BSL8
29+import Data.Coerce (coerce)
3530import qualified Data.Foldable as F
31+import Data.Functor.Identity (Identity(Identity))
3632import Data.Hashable (Hashable)
3733import Data.HashMap.Strict (HashMap)
3834import qualified Data.HashMap.Strict as HashMap
39−import Data.Int
35+import Data.Int (Int16, Int32, Int64, Int8)
4036import Data.IntMap (IntMap)
4137import qualified Data.IntMap as IntMap
42−import Data.List (intersperse)
38+import Data.List (intersperse, sortBy)
4339import Data.Map (Map)
4440import qualified Data.Map as Map
45−import Data.Monoid
46−
41+import Data.Monoid (All (..), Any (..), Dual (..),
42+ Product (..), Sum (..))
43+import Data.Ord (comparing)
44+import Data.Proxy (Proxy (..))
45+import Data.Semigroup (Semigroup (..))
46+import qualified Data.Semigroup as Semi
47+import Data.Tagged (Tagged (..))
4748import Data.Text (Text)
4849import qualified Data.Text as Text
49−import qualified Data.Text.Lazy as Lazy
50−import Data.Text.Encoding as Text
50+import qualified Data.Text.Encoding as Text
5151import Data.Text.Encoding.Error (lenientDecode)
52−
53−import Data.Time
54−import Data.Proxy
55−import Data.Word
56−
57−#if MIN_VERSION_base(4,8,0)
58−import Data.Void
59−import Numeric.Natural
60−#endif
61−
52+import qualified Data.Text.Lazy as Lazy
53+import Data.Time.Compat (Day, LocalTime, NominalDiffTime,
54+ UTCTime, ZonedTime)
55+import Data.Time.Calendar.Month.Compat (Month)
56+import Data.Time.Calendar.Quarter.Compat (Quarter, QuarterOfYear (..))
57+import Data.Void (Void)
58+import Data.Word (Word16, Word32, Word64, Word8)
59+import GHC.Exts (Constraint, IsList (..))
6260import GHC.Generics
63−import URI.ByteString (urlEncodeQuery, urlDecodeQuery)
64−
65−import Web.Internal.HttpApiData
61+import GHC.TypeLits
62+import Network.HTTP.Types.URI (urlDecode, urlEncodeBuilder)
63+import Numeric.Natural (Natural)
64+import Web.Internal.HttpApiData
6665
6766-- $setup
6867-- >>> :set -XDeriveGeneric
@@ -71,11 +70,20 @@ import Web.Internal.HttpApiData
7170-- >>> :set -XFlexibleContexts
7271-- >>> :set -XScopedTypeVariables
7372-- >>> :set -XTypeFamilies
74−-- >>> import Data.Either (isLeft)
75−-- >>> import Data.List (sort)
73+-- >>> import Data.Char (toLower)
74+--
7675-- >>> data Person = Person { name :: String, age :: Int } deriving (Show, Generic)
7776-- >>> instance ToForm Person
7877-- >>> instance FromForm Person
78+--
79+-- >>> data Post = Post { title :: String, subtitle :: Maybe String, comments :: [String]} deriving (Generic, Show)
80+-- >>> instance ToForm Post
81+-- >>> instance FromForm Post
82+--
83+-- >>> data Project = Project { projectName :: String, projectSize :: Int } deriving (Generic, Show)
84+-- >>> let myOptions = FormOptions { fieldLabelModifier = map toLower . drop (length ("project" :: String)) }
85+-- >>> instance ToForm Project where toForm = genericToForm myOptions
86+-- >>> instance FromForm Project where fromForm = genericFromForm myOptions
7987
8088-- | Typeclass for types that can be used as keys in a 'Form'-like container (like 'Map').
8189class ToFormKey k where
@@ -107,6 +115,9 @@ instance ToFormKey LocalTime where toFormKey = toQueryParam
107115instance ToFormKey ZonedTime where toFormKey = toQueryParam
108116instance ToFormKey UTCTime where toFormKey = toQueryParam
109117instance ToFormKey NominalDiffTime where toFormKey = toQueryParam
118+instance ToFormKey Quarter where toFormKey = toQueryParam
119+instance ToFormKey QuarterOfYear where toFormKey = toQueryParam
120+instance ToFormKey Month where toFormKey = toQueryParam
110121
111122instance ToFormKey String where toFormKey = toQueryParam
112123instance ToFormKey Text where toFormKey = toQueryParam
@@ -115,14 +126,26 @@ instance ToFormKey Lazy.Text where toFormKey = toQueryParam
115126instance ToFormKey All where toFormKey = toQueryParam
116127instance ToFormKey Any where toFormKey = toQueryParam
117128
118−instance ToFormKey a => ToFormKey (Dual a) where toFormKey = toFormKey . getDual
119−instance ToFormKey a => ToFormKey (Sum a) where toFormKey = toFormKey . getSum
120−instance ToFormKey a => ToFormKey (Product a) where toFormKey = toFormKey . getProduct
129+instance ToFormKey a => ToFormKey (Dual a) where toFormKey = coerce (toFormKey :: a -> Text)
130+instance ToFormKey a => ToFormKey (Sum a) where toFormKey = coerce (toFormKey :: a -> Text)
131+instance ToFormKey a => ToFormKey (Product a) where toFormKey = coerce (toFormKey :: a -> Text)
132+
133+instance ToFormKey a => ToFormKey (Semi.Min a) where toFormKey = coerce (toFormKey :: a -> Text)
134+instance ToFormKey a => ToFormKey (Semi.Max a) where toFormKey = coerce (toFormKey :: a -> Text)
135+instance ToFormKey a => ToFormKey (Semi.First a) where toFormKey = coerce (toFormKey :: a -> Text)
136+instance ToFormKey a => ToFormKey (Semi.Last a) where toFormKey = coerce (toFormKey :: a -> Text)
137+
138+instance ToFormKey a => ToFormKey (Tagged b a) where toFormKey = coerce (toFormKey :: a -> Text)
139+
140+-- | @since 0.4.2
141+instance ToFormKey a => ToFormKey (Identity a) where toFormKey = coerce (toFormKey :: a -> Text)
142+
143+-- | @since 0.4.2
144+instance ToFormKey a => ToFormKey (Const a b) where
145+ toFormKey = coerce (toFormKey :: a -> Text)
121146
122−#if MIN_VERSION_base(4,8,0)
123147instance ToFormKey Void where toFormKey = toQueryParam
124148instance ToFormKey Natural where toFormKey = toQueryParam
125−#endif
126149
127150-- | Typeclass for types that can be parsed from keys of a 'Form'. This is the reverse of 'ToFormKey'.
128151class FromFormKey k where
@@ -154,6 +177,9 @@ instance FromFormKey LocalTime where parseFormKey = parseQueryParam
154177instance FromFormKey ZonedTime where parseFormKey = parseQueryParam
155178instance FromFormKey UTCTime where parseFormKey = parseQueryParam
156179instance FromFormKey NominalDiffTime where parseFormKey = parseQueryParam
180+instance FromFormKey Quarter where parseFormKey = parseQueryParam
181+instance FromFormKey QuarterOfYear where parseFormKey = parseQueryParam
182+instance FromFormKey Month where parseFormKey = parseQueryParam
157183
158184instance FromFormKey String where parseFormKey = parseQueryParam
159185instance FromFormKey Text where parseFormKey = parseQueryParam
@@ -162,30 +188,48 @@ instance FromFormKey Lazy.Text where parseFormKey = parseQueryParam
162188instance FromFormKey All where parseFormKey = parseQueryParam
163189instance FromFormKey Any where parseFormKey = parseQueryParam
164190
165−instance FromFormKey a => FromFormKey (Dual a) where parseFormKey = fmap Dual . parseFormKey
166−instance FromFormKey a => FromFormKey (Sum a) where parseFormKey = fmap Sum . parseFormKey
167−instance FromFormKey a => FromFormKey (Product a) where parseFormKey = fmap Product . parseFormKey
191+instance FromFormKey a => FromFormKey (Dual a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
192+instance FromFormKey a => FromFormKey (Sum a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
193+instance FromFormKey a => FromFormKey (Product a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
194+
195+instance FromFormKey a => FromFormKey (Semi.Min a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
196+instance FromFormKey a => FromFormKey (Semi.Max a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
197+instance FromFormKey a => FromFormKey (Semi.First a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
198+instance FromFormKey a => FromFormKey (Semi.Last a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
199+
200+instance FromFormKey a => FromFormKey (Tagged b a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
201+
202+-- | @since 0.4.2
203+instance FromFormKey a => FromFormKey (Identity a) where parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
204+
205+-- | @since 0.4.2
206+instance FromFormKey a => FromFormKey (Const a b) where
207+ parseFormKey = coerce (parseFormKey :: Text -> Either Text a)
168208
169−#if MIN_VERSION_base(4,8,0)
170209instance FromFormKey Void where parseFormKey = parseQueryParam
171210instance FromFormKey Natural where parseFormKey = parseQueryParam
172−#endif
173211
174212-- | The contents of a form, not yet URL-encoded.
175213--
176214-- 'Form' can be URL-encoded with 'urlEncodeForm' and URL-decoded with 'urlDecodeForm'.
177215newtype Form = Form { unForm :: HashMap Text [Text] }
178− deriving (Eq, Read, Generic, Monoid)
216+ deriving (Eq, Read, Generic, Semigroup, Monoid)
179217
180218instance Show Form where
181219 showsPrec d form = showParen (d > 10) $
182− showString "fromList " . shows (toList form)
220+ showString "fromList " . shows (toListStable form)
183221
222+-- | _NOTE:_ 'toList' is unstable and may result in different key order (but not values).
223+-- For a stable conversion use 'toListStable'.
184224instance IsList Form where
185225 type Item Form = (Text, Text)
186226 fromList = Form . HashMap.fromListWith (flip (<>)) . fmap (\(k, v) -> (k, [v]))
187227 toList = concatMap (\(k, vs) -> map ((,) k) vs) . HashMap.toList . unForm
188228
229+-- | A stable version of 'toList'.
230+toListStable :: Form -> [(Text, Text)]
231+toListStable = sortOn fst . toList
232+
189233-- | Convert a value into 'Form'.
190234--
191235-- An example type and instance:
@@ -222,7 +266,6 @@ instance IsList Form where
222266-- @
223267--
224268-- The default implementation of 'toForm' is 'genericToForm'.
225−-- It only works for records and it will use 'toQueryParam' for each field's value.
226269class ToForm a where
227270 -- | Convert a value into 'Form'.
228271 toForm :: a -> Form
@@ -254,6 +297,8 @@ data Proxy3 a b c = Proxy3
254297
255298type family NotSupported (cls :: k1) (a :: k2) (reason :: Symbol) :: Constraint where
256299#if __GLASGOW_HASKELL__ < 800
300+ -- this is just a placeholder case for older GHCs to not freak out on an empty closed type family
301+ NotSupported cls a "this type family is actually empty" = ()
257302#else
258303 NotSupported cls a reason = TypeError
259304 ( 'Text "Cannot derive a Generic-based " ':<>: 'ShowType cls ':<>: 'Text " instance for " ':<>: 'ShowType a ':<>: 'Text "." ':$$:
@@ -273,6 +318,30 @@ type family NotSupported (cls :: k1) (a :: k2) (reason :: Symbol) :: Constraint
273318-- , age :: Int
274319-- } deriving ('Generic')
275320-- @
321+--
322+-- In this implementation each field's value gets encoded using `toQueryParam`.
323+-- Two field types are exceptions:
324+--
325+-- - for values of type @'Maybe' a@ an entry is added to the 'Form' only when it is @'Just' x@
326+-- and the encoded value is @'toQueryParam' x@; 'Nothing' values are omitted from the 'Form';
327+--
328+-- - for values of type @[a]@ (except @['Char']@) an entry is added for every item in the list;
329+-- if the list is empty no entries are added to the 'Form';
330+--
331+-- Here's an example:
332+--
333+-- @
334+-- data Post = Post
335+-- { title :: String
336+-- , subtitle :: Maybe String
337+-- , comments :: [String]
338+-- } deriving ('Generic', 'Show')
339+--
340+-- instance 'ToForm' Post
341+-- @
342+--
343+-- >>> urlEncodeAsFormStable Post { title = "Test", subtitle = Nothing, comments = ["Nice post!", "+1"] }
344+-- "comments=Nice%20post%21&comments=%2B1&title=Test"
276345genericToForm :: forall a. (Generic a, GToForm a (Rep a)) => FormOptions -> a -> Form
277346genericToForm opts = gToForm (Proxy :: Proxy a) opts . from
278347
@@ -288,7 +357,25 @@ instance (GToForm t f) => GToForm t (M1 D x f) where
288357instance (GToForm t f) => GToForm t (M1 C x f) where
289358 gToForm p opts (M1 a) = gToForm p opts a
290359
291−instance (Selector s, ToHttpApiData c) => GToForm t (M1 S s (K1 i c)) where
360+instance OVERLAPPABLE_ (Selector s, ToHttpApiData c) => GToForm t (M1 S s (K1 i c)) where
361+ gToForm _ opts (M1 (K1 c)) = fromList [(key, toQueryParam c)]
362+ where
363+ key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
364+
365+instance (Selector s, ToHttpApiData c) => GToForm t (M1 S s (K1 i (Maybe c))) where
366+ gToForm _ opts (M1 (K1 c)) =
367+ case c of
368+ Nothing -> mempty
369+ Just x -> fromList [(key, toQueryParam x)]
370+ where
371+ key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
372+
373+instance (Selector s, ToHttpApiData c) => GToForm t (M1 S s (K1 i [c])) where
374+ gToForm _ opts (M1 (K1 cs)) = fromList (map (\c -> (key, toQueryParam c)) cs)
375+ where
376+ key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
377+
378+instance OVERLAPPING_ (Selector s) => GToForm t (M1 S s (K1 i String)) where
292379 gToForm _ opts (M1 (K1 c)) = fromList [(key, toQueryParam c)]
293380 where
294381 key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
@@ -305,9 +392,9 @@ instance NotSupported ToForm t "is a sum type" => GToForm t (f :+: g) where gToF
305392-- , age :: Int }
306393--
307394-- instance 'FromForm' Person where
308−-- 'fromForm' (Form m) = Person
309−-- '<$>' 'parseUnique' "name" m
310−-- '<*>' 'parseUnique' "age" m
395+-- 'fromForm' f = Person
396+-- '<$>' 'parseUnique' "name" f
397+-- '<*>' 'parseUnique' "age" f
311398-- @
312399--
313400-- Instead of manually writing @'FromForm'@ instances you can
@@ -338,6 +425,7 @@ class FromForm a where
338425
339426instance FromForm Form where fromForm = pure
340427
428+-- | _NOTE:_ this conversion is unstable and may result in different key order (but not values).
341429instance (FromFormKey k, FromHttpApiData v) => FromForm [(k, v)] where
342430 fromForm = fmap (concatMap (\(k, vs) -> map ((,) k) vs)) . toEntriesByKey
343431
@@ -352,13 +440,22 @@ instance FromHttpApiData v => FromForm (IntMap [v]) where
352440
353441-- | Parse a 'Form' into a list of entries groupped by key.
354442--
355−-- >>> toEntriesByKey [("name", "Nick"), ("color", "red"), ("color", "white")] :: Either Text [(Text, [Text])]
356−-- Right [("color",["red","white"]),("name",["Nick"])]
443+-- _NOTE:_ this conversion is unstable and may result in different key order
444+-- (but not values). For a stable encoding see 'toEntriesByKeyStable'.
357445toEntriesByKey :: (FromFormKey k, FromHttpApiData v) => Form -> Either Text [(k, [v])]
358446toEntriesByKey = traverse parseGroup . HashMap.toList . unForm
359447 where
360448 parseGroup (k, vs) = (,) <$> parseFormKey k <*> traverse parseQueryParam vs
361449
450+-- | Parse a 'Form' into a list of entries groupped by key.
451+--
452+-- >>> toEntriesByKeyStable [("name", "Nick"), ("color", "red"), ("color", "white")] :: Either Text [(Text, [Text])]
453+-- Right [("color",["red","white"]),("name",["Nick"])]
454+--
455+-- For an unstable (but faster) conversion see 'toEntriesByKey'.
456+toEntriesByKeyStable :: (Ord k, FromFormKey k, FromHttpApiData v) => Form -> Either Text [(k, [v])]
457+toEntriesByKeyStable = fmap (sortOn fst) . toEntriesByKey
458+
362459-- | A 'Generic'-based implementation of 'fromForm'.
363460-- This is used as a default implementation in 'FromForm'.
364461--
@@ -370,6 +467,29 @@ toEntriesByKey = traverse parseGroup . HashMap.toList . unForm
370467-- , age :: Int
371468-- } deriving ('Generic')
372469-- @
470+--
471+-- In this implementation each field's value gets decoded using `parseQueryParam`.
472+-- Two field types are exceptions:
473+--
474+-- - for values of type @'Maybe' a@ an entry is parsed if present in the 'Form'
475+-- and the is decoded with 'parseQueryParam'; if no entry is present result is 'Nothing';
476+--
477+-- - for values of type @[a]@ (except @['Char']@) all entries are parsed to produce a list of parsed values;
478+--
479+-- Here's an example:
480+--
481+-- @
482+-- data Post = Post
483+-- { title :: String
484+-- , subtitle :: Maybe String
485+-- , comments :: [String]
486+-- } deriving ('Generic', 'Show')
487+--
488+-- instance 'FromForm' Post
489+-- @
490+--
491+-- >>> urlDecodeAsForm "comments=Nice%20post%21&comments=%2B1&title=Test" :: Either Text Post
492+-- Right (Post {title = "Test", subtitle = Nothing, comments = ["Nice post!","+1"]})
373493genericFromForm :: forall a. (Generic a, GFromForm a (Rep a)) => FormOptions -> Form -> Either Text a
374494genericFromForm opts f = to <$> gFromForm (Proxy :: Proxy a) opts f
375495
@@ -379,54 +499,83 @@ class GFromForm t (f :: * -> *) where
379499instance (GFromForm t f, GFromForm t g) => GFromForm t (f :*: g) where
380500 gFromForm p opts f = (:*:) <$> gFromForm p opts f <*> gFromForm p opts f
381501
382−instance (Selector s, FromHttpApiData f) => GFromForm t (M1 S s (K1 i f)) where
383− gFromForm _ opts form = M1 . K1 <$> parseUnique key form
384− where
385− key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
386−
387502instance GFromForm t f => GFromForm t (M1 D x f) where
388503 gFromForm p opts f = M1 <$> gFromForm p opts f
389504
390505instance GFromForm t f => GFromForm t (M1 C x f) where
391506 gFromForm p opts f = M1 <$> gFromForm p opts f
392507
508+instance OVERLAPPABLE_ (Selector s, FromHttpApiData c) => GFromForm t (M1 S s (K1 i c)) where
509+ gFromForm _ opts form = M1 . K1 <$> parseUnique key form
510+ where
511+ key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
512+
513+instance (Selector s, FromHttpApiData c) => GFromForm t (M1 S s (K1 i (Maybe c))) where
514+ gFromForm _ opts form = M1 . K1 <$> parseMaybe key form
515+ where
516+ key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
517+
518+instance (Selector s, FromHttpApiData c) => GFromForm t (M1 S s (K1 i [c])) where
519+ gFromForm _ opts form = M1 . K1 <$> parseAll key form
520+ where
521+ key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
522+
523+instance OVERLAPPING_ (Selector s) => GFromForm t (M1 S s (K1 i String)) where
524+ gFromForm _ opts form = M1 . K1 <$> parseUnique key form
525+ where
526+ key = Text.pack $ fieldLabelModifier opts $ selName (Proxy3 :: Proxy3 s g p)
527+
393528instance NotSupported FromForm t "is a sum type" => GFromForm t (f :+: g) where gFromForm = error "impossible"
394529
395530-- | Encode a 'Form' to an @application/x-www-form-urlencoded@ 'BSL.ByteString'.
396531--
532+-- _NOTE:_ this encoding is unstable and may result in different key order
533+-- (but not values). For a stable encoding see 'urlEncodeFormStable'.
534+urlEncodeForm :: Form -> BSL.ByteString
535+urlEncodeForm = urlEncodeParams . toList
536+
537+-- | Encode a 'Form' to an @application/x-www-form-urlencoded@ 'BSL.ByteString'.
538+--
539+-- For an unstable (but faster) encoding see 'urlEncodeForm'.
540+--
397541-- Key-value pairs get encoded to @key=value@ and separated by @&@:
398542--
399−-- >>> urlEncodeForm [("name", "Julian"), ("lastname", "Arni")]
543+-- >>> urlEncodeFormStable [("name", "Julian"), ("lastname", "Arni")]
400544-- "lastname=Arni&name=Julian"
401545--
402546-- Keys with empty values get encoded to just @key@ (without the @=@ sign):
403547--
404−-- >>> urlEncodeForm [("is_test", "")]
548+-- >>> urlEncodeFormStable [("is_test", "")]
405549-- "is_test"
406550--
407551-- Empty keys are allowed too:
408552--
409−-- >>> urlEncodeForm [("", "foobar")]
553+-- >>> urlEncodeFormStable [("", "foobar")]
410554-- "=foobar"
411555--
412−-- However, if not key and value are empty, the key-value pair is ignored.
413−-- (This prevents @'urlDecodeForm' . 'urlEncodeForm'@ from being a true isomorphism).
556+-- However, if both key and value are empty, the key-value pair is ignored.
557+-- (This prevents @'urlDecodeForm' . 'urlEncodeFormStable'@ from being a true isomorphism).
414558--
415−-- >>> urlEncodeForm [("", "")]
559+-- >>> urlEncodeFormStable [("", "")]
416560-- ""
417561--
418562-- Everything is escaped with @'escapeURIString' 'isUnreserved'@:
419563--
420−-- >>> urlEncodeForm [("fullname", "Andres Löh")]
564+-- >>> urlEncodeFormStable [("fullname", "Andres Löh")]
421565-- "fullname=Andres%20L%C3%B6h"
422−urlEncodeForm :: Form -> BSL.ByteString
423−urlEncodeForm = toLazyByteString . mconcat . intersperse (shortByteString "&") . map encodePair . toList
566+urlEncodeFormStable :: Form -> BSL.ByteString
567+urlEncodeFormStable = urlEncodeParams . sortOn fst . toList
568+
569+-- | Encode a list of key-value pairs to an @application/x-www-form-urlencoded@ 'BSL.ByteString'.
570+--
571+-- See also 'urlEncodeFormStable'.
572+urlEncodeParams :: [(Text, Text)] -> BSL.ByteString
573+urlEncodeParams = toLazyByteString . mconcat . intersperse (shortByteString "&") . map encodePair
424574 where
425− escape = urlEncodeQuery . Text.encodeUtf8
575+ escape = urlEncodeBuilder True . Text.encodeUtf8
426576
427577 encodePair (k, "") = escape k
428− encodePair (k, v) = escape k <> shortByteString "=" <> escape v
429−
578+ encodePair (k, v) = escape k <> shortByteString "=" <> escape v
430579
431580-- | Decode an @application/x-www-form-urlencoded@ 'BSL.ByteString' to a 'Form'.
432581--
@@ -460,11 +609,17 @@ urlEncodeForm = toLazyByteString . mconcat . intersperse (shortByteString "&") .
460609-- >>> urlDecodeForm "this=has=too=many=equals"
461610-- Left "not a valid pair: this=has=too=many=equals"
462611urlDecodeForm :: BSL.ByteString -> Either Text Form
463−urlDecodeForm bs = toForm <$> traverse parsePair pairs
612+urlDecodeForm = fmap toForm . urlDecodeParams
613+
614+-- | Decode an @application/x-www-form-urlencoded@ 'BSL.ByteString' to a list of key-value pairs.
615+--
616+-- See also 'urlDecodeForm'.
617+urlDecodeParams :: BSL.ByteString -> Either Text [(Text, Text)]
618+urlDecodeParams bs = traverse parsePair pairs
464619 where
465620 pairs = map (BSL8.split '=') (BSL8.split '&' bs)
466621
467− unescape = Text.decodeUtf8With lenientDecode . urlDecodeQuery . BSL.toStrict
622+ unescape = Text.decodeUtf8With lenientDecode . urlDecode True . BSL.toStrict
468623
469624 parsePair p =
470625 case map unescape p of
@@ -472,6 +627,7 @@ urlDecodeForm bs = toForm <$> traverse parsePair pairs
472627 [k] -> return (k, "")
473628 xs -> Left $ "not a valid pair: " <> Text.intercalate "=" xs
474629
630+
475631-- | This is a convenience function for decoding a
476632-- @application/x-www-form-urlencoded@ 'BSL.ByteString' directly to a datatype
477633-- that has an instance of 'FromForm'.
@@ -489,11 +645,22 @@ urlDecodeAsForm = fromForm <=< urlDecodeForm
489645--
490646-- This is effectively @'urlEncodeForm' . 'toForm'@.
491647--
492−-- >>> urlEncodeAsForm Person {name = "Dennis", age = 22}
493−-- "age=22&name=Dennis"
648+-- _NOTE:_ this encoding is unstable and may result in different key order
649+-- (but not values). For a stable encoding see 'urlEncodeAsFormStable'.
494650urlEncodeAsForm :: ToForm a => a -> BSL.ByteString
495651urlEncodeAsForm = urlEncodeForm . toForm
496652
653+-- | This is a convenience function for encoding a datatype that has instance
654+-- of 'ToForm' directly to a @application/x-www-form-urlencoded@
655+-- 'BSL.ByteString'.
656+--
657+-- This is effectively @'urlEncodeFormStable' . 'toForm'@.
658+--
659+-- >>> urlEncodeAsFormStable Person {name = "Dennis", age = 22}
660+-- "age=22&name=Dennis"
661+urlEncodeAsFormStable :: ToForm a => a -> BSL.ByteString
662+urlEncodeAsFormStable = urlEncodeFormStable . toForm
663+
497664-- | Find all values corresponding to a given key in a 'Form'.
498665--
499666-- >>> lookupAll "name" []
@@ -505,6 +672,22 @@ urlEncodeAsForm = urlEncodeForm . toForm
505672lookupAll :: Text -> Form -> [Text]
506673lookupAll key = F.concat . HashMap.lookup key . unForm
507674
675+-- | Lookup an optional value for a key.
676+-- Fail if there is more than one value.
677+--
678+-- >>> lookupMaybe "name" []
679+-- Right Nothing
680+-- >>> lookupMaybe "name" [("name", "Oleg")]
681+-- Right (Just "Oleg")
682+-- >>> lookupMaybe "name" [("name", "Oleg"), ("name", "David")]
683+-- Left "Duplicate key \"name\""
684+lookupMaybe :: Text -> Form -> Either Text (Maybe Text)
685+lookupMaybe key form =
686+ case lookupAll key form of
687+ [] -> pure Nothing
688+ [v] -> pure (Just v)
689+ _ -> Left $ "Duplicate key " <> Text.pack (show key)
690+
508691-- | Lookup a unique value for a key.
509692-- Fail if there is zero or more than one value.
510693--
@@ -515,11 +698,11 @@ lookupAll key = F.concat . HashMap.lookup key . unForm
515698-- >>> lookupUnique "name" [("name", "Oleg"), ("name", "David")]
516699-- Left "Duplicate key \"name\""
517700lookupUnique :: Text -> Form -> Either Text Text
518−lookupUnique key form =
519− case lookupAll key form of
520− [v] -> pure v
521− [] -> Left $ "Could not find key " <> Text.pack (show key)
522− _ -> Left $ "Duplicate key " <> Text.pack (show key)
701+lookupUnique key form = do
702+ mv <- lookupMaybe key form
703+ case mv of
704+ Just v -> pure v
705+ Nothing -> Left $ "Could not find key " <> Text.pack (show key)
523706
524707-- | Lookup all values for a given key in a 'Form' and parse them with 'parseQueryParams'.
525708--
@@ -534,6 +717,22 @@ lookupUnique key form =
534717parseAll :: FromHttpApiData v => Text -> Form -> Either Text [v]
535718parseAll key = parseQueryParams . lookupAll key
536719
720+-- | Lookup an optional value for a given key and parse it with 'parseQueryParam'.
721+-- Fail if there is more than one value for the key.
722+--
723+-- >>> parseMaybe "age" [] :: Either Text (Maybe Word8)
724+-- Right Nothing
725+-- >>> parseMaybe "age" [("age", "12"), ("age", "25")] :: Either Text (Maybe Word8)
726+-- Left "Duplicate key \"age\""
727+-- >>> parseMaybe "age" [("age", "seven")] :: Either Text (Maybe Word8)
728+-- Left "could not parse: `seven' (input does not start with a digit)"
729+-- >>> parseMaybe "age" [("age", "777")] :: Either Text (Maybe Word8)
730+-- Left "out of bounds: `777' (should be between 0 and 255)"
731+-- >>> parseMaybe "age" [("age", "7")] :: Either Text (Maybe Word8)
732+-- Right (Just 7)
733+parseMaybe :: FromHttpApiData v => Text -> Form -> Either Text (Maybe v)
734+parseMaybe key = parseQueryParams <=< lookupMaybe key
735+
537736-- | Lookup a unique value for a given key and parse it with 'parseQueryParam'.
538737-- Fail if there is zero or more than one value for the key.
539738--
@@ -551,6 +750,31 @@ parseUnique :: FromHttpApiData v => Text -> Form -> Either Text v
551750parseUnique key form = lookupUnique key form >>= parseQueryParam
552751
553752-- | 'Generic'-based deriving options for 'ToForm' and 'FromForm'.
753+--
754+-- A common use case for non-default 'FormOptions'
755+-- is to strip a prefix off of field labels:
756+--
757+-- @
758+-- data Project = Project
759+-- { projectName :: String
760+-- , projectSize :: Int
761+-- } deriving ('Generic', 'Show')
762+--
763+-- myOptions :: 'FormOptions'
764+-- myOptions = 'FormOptions'
765+-- { 'fieldLabelModifier' = 'map' 'toLower' . 'drop' ('length' \"project\") }
766+--
767+-- instance 'ToForm' Project where
768+-- 'toForm' = 'genericToForm' myOptions
769+--
770+-- instance 'FromForm' Project where
771+-- 'fromForm' = 'genericFromForm' myOptions
772+-- @
773+--
774+-- >>> urlEncodeAsFormStable Project { projectName = "http-api-data", projectSize = 172 }
775+-- "name=http-api-data&size=172"
776+-- >>> urlDecodeAsForm "name=http-api-data&size=172" :: Either Text Project
777+-- Right (Project {projectName = "http-api-data", projectSize = 172})
554778data FormOptions = FormOptions
555779 { -- | Function applied to field labels. Handy for removing common record prefixes for example.
556780 fieldLabelModifier :: String -> String
@@ -567,3 +791,6 @@ defaultFormOptions :: FormOptions
567791defaultFormOptions = FormOptions
568792 { fieldLabelModifier = id
569793 }
794+
795+sortOn :: Ord b => (a -> b) -> [a] -> [a]
796+sortOn f = sortBy (comparing f)