{-# LANGUAGE CPP #-} {-# LANGUAGE PatternGuards #-} {-# LANGUAGE TemplateHaskell #-} {-# LANGUAGE FunctionalDependencies #-} #ifdef TRUSTWORTHY {-# LANGUAGE Trustworthy #-} #endif #ifndef MIN_VERSION_template_haskell #define MIN_VERSION_template_haskell(x,y,z) (defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 706) #endif ----------------------------------------------------------------------------- -- | -- Module : Control.Lens.TH -- Copyright : (C) 2012-14 Edward Kmett, Michael Sloan -- License : BSD-style (see the file LICENSE) -- Maintainer : Edward Kmett <ekmett@gmail.com> -- Stability : experimental -- Portability : non-portable -- ----------------------------------------------------------------------------- module Control.Lens.TH ( -- * Constructing Lenses Automatically makeLenses, makeLensesFor , makeClassy, makeClassyFor, makeClassy_ , makePrisms , makeWrapped , makeFields -- * Constructing Lenses Given a Declaration Quote , declareLenses, declareLensesFor , declareClassy, declareClassyFor , declarePrisms , declareWrapped , declareFields -- * Configuring Lenses , makeLensesWith , makeFieldsWith , declareLensesWith , declareFieldsWith , defaultRules , defaultFieldRules , camelCaseFields , underscoreFields , LensRules(LensRules) , FieldRules(FieldRules) , lensRules , classyRules , classyRules_ , lensIso , lensField , lensClass , lensFlags , LensFlag(..) , simpleLenses , partialLenses , buildTraversals , handleSingletons , singletonIso , singletonRequired , createClass , createInstance , classRequired , singletonAndField , generateSignatures ) where import Control.Applicative import Control.Monad ((<=<), when, replicateM) #if !(MIN_VERSION_template_haskell(2,7,0)) import Control.Monad (ap) #endif import qualified Control.Monad.Trans as Trans import Control.Monad.Trans.Writer import Control.Lens.At import Control.Lens.Fold import Control.Lens.Getter import Control.Lens.Iso import Control.Lens.Lens import Control.Lens.Prism import Control.Lens.Review import Control.Lens.Setter import Control.Lens.Tuple import Control.Lens.Traversal import Control.Lens.Wrapped import Control.Lens.Internal.TH import Data.Char (toLower, toUpper, isUpper) import Data.Either (lefts) import Data.Foldable hiding (concat, any) import Data.Function (on) import Data.List as List import Data.Map as Map hiding (toList,map,filter) import Data.Maybe as Maybe (isNothing,isJust,catMaybes,fromJust,mapMaybe) import Data.Monoid import Data.Ord (comparing) import Data.Set as Set hiding (toList,map,filter) import Data.Set.Lens import Data.Traversable hiding (mapM) import Language.Haskell.TH import Language.Haskell.TH.Syntax import Language.Haskell.TH.Lens #ifdef HLINT {-# ANN module "HLint: ignore Eta reduce" #-} {-# ANN module "HLint: ignore Use fewer imports" #-} {-# ANN module "HLint: ignore Use foldl" #-} #endif -- | Flags for 'Lens' construction data LensFlag = SimpleLenses | PartialLenses | BuildTraversals | SingletonAndField | SingletonIso | HandleSingletons | SingletonRequired | CreateClass | CreateInstance | ClassRequired | GenerateSignatures deriving (Eq,Ord,Show,Read) -- | Only Generate valid 'Control.Lens.Type.Simple' lenses. simpleLenses :: Lens' LensRules Bool simpleLenses = lensFlags.contains SimpleLenses -- | Enables the generation of partial lenses, generating runtime errors for -- every constructor that does not have a valid definition for the 'Lens'. This -- occurs when the constructor lacks the field, or has multiple fields mapped -- to the same 'Lens'. partialLenses :: Lens' LensRules Bool partialLenses = lensFlags.contains PartialLenses -- | In the situations that a 'Lens' would be partial, when 'partialLenses' is -- used, this flag instead causes traversals to be generated. Only one can be -- used, and if neither are, then compile-time errors are generated. buildTraversals :: Lens' LensRules Bool buildTraversals = lensFlags.contains BuildTraversals -- | Handle singleton constructors specially. handleSingletons :: Lens' LensRules Bool handleSingletons = lensFlags.contains HandleSingletons -- | When building a singleton 'Iso' (or 'Lens') for a record constructor, build -- both the 'Iso' (or 'Lens') for the record and the one for the field. singletonAndField :: Lens' LensRules Bool singletonAndField = lensFlags.contains SingletonAndField -- | Use 'Iso' for singleton constructors. singletonIso :: Lens' LensRules Bool singletonIso = lensFlags.contains SingletonIso -- | Expect a single constructor, single field newtype or data type. singletonRequired :: Lens' LensRules Bool singletonRequired = lensFlags.contains SingletonRequired -- | Create the class if the constructor is 'Control.Lens.Type.Simple' and the 'lensClass' rule matches. createClass :: Lens' LensRules Bool createClass = lensFlags.contains CreateClass -- | Create the instance if the constructor is 'Control.Lens.Type.Simple' and the 'lensClass' rule matches. createInstance :: Lens' LensRules Bool createInstance = lensFlags.contains CreateInstance -- | Die if the 'lensClass' fails to match. classRequired :: Lens' LensRules Bool classRequired = lensFlags.contains ClassRequired -- | Indicate whether or not to supply the signatures for the generated -- lenses. -- -- Disabling this can be useful if you want to provide a more restricted type -- signature or if you want to supply hand-written haddocks. generateSignatures :: Lens' LensRules Bool generateSignatures = lensFlags.contains GenerateSignatures -- | This configuration describes the options we'll be using to make -- isomorphisms or lenses. data LensRules = LensRules { _lensIso :: String -> Maybe String , _lensField :: String -> Maybe String , _lensClass :: String -> Maybe (String, String) , _lensFlags :: Set LensFlag } -- | 'Lens'' to access the convention for naming top level isomorphisms in our -- 'LensRules'. -- -- Defaults to lowercasing the first letter of the constructor. lensIso :: Lens' LensRules (String -> Maybe String) lensIso f (LensRules i n c o) = f i <&> \i' -> LensRules i' n c o -- | 'Lens'' to access the convention for naming fields in our 'LensRules'. -- -- Defaults to stripping the _ off of the field name, lowercasing the name, and -- rejecting the field if it doesn't start with an '_'. lensField :: Lens' LensRules (String -> Maybe String) lensField f (LensRules i n c o) = f n <&> \n' -> LensRules i n' c o -- | Retrieve options such as the name of the class and method to put in it to -- build a class around monomorphic data types. lensClass :: Lens' LensRules (String -> Maybe (String, String)) lensClass f (LensRules i n c o) = f c <&> \c' -> LensRules i n c' o -- | Retrieve options such as the name of the class and method to put in it to -- build a class around monomorphic data types. lensFlags :: Lens' LensRules (Set LensFlag) lensFlags f (LensRules i n c o) = f o <&> LensRules i n c -- | Default 'LensRules'. defaultRules :: LensRules defaultRules = LensRules mLowerName fld (const Nothing) $ Set.fromList [SingletonIso, SingletonAndField, CreateClass, CreateInstance, BuildTraversals, GenerateSignatures] where fld ('_':cs) = mLowerName cs fld _ = Nothing mLowerName :: String -> Maybe String mLowerName (c:cs) = Just (toLower c:cs) mLowerName _ = Nothing -- | Rules for making fairly simple partial lenses, ignoring the special cases -- for isomorphisms and traversals, and not making any classes. lensRules :: LensRules lensRules = defaultRules & lensIso .~ const Nothing & lensClass .~ const Nothing & handleSingletons .~ True & partialLenses .~ False & buildTraversals .~ True lensRulesFor :: [(String, String)] -> LensRules lensRulesFor fields = lensRules & lensField .~ (`Prelude.lookup` fields) -- | Rules for making lenses and traversals that precompose another 'Lens'. classyRules :: LensRules classyRules = defaultRules & lensIso .~ const Nothing & handleSingletons .~ False & lensClass .~ classy & classRequired .~ True & partialLenses .~ False & buildTraversals .~ True where classy :: String -> Maybe (String, String) classy n@(a:as) = Just ("Has" ++ n, toLower a:as) classy _ = Nothing classyRulesFor :: (String -> Maybe (String, String)) -> [(String, String)] -> LensRules classyRulesFor classFun fields = classyRules & lensClass .~ classFun & lensField .~ (`Prelude.lookup` fields) underscorePrefixRules :: LensRules underscorePrefixRules = LensRules mLowerName fld (const Nothing) $ Set.fromList [SingletonIso, SingletonAndField, CreateClass, CreateInstance, BuildTraversals, GenerateSignatures] where fld cs = Just ('_':cs) classyRules_ :: LensRules classyRules_ = underscorePrefixRules & lensIso .~ const Nothing & handleSingletons .~ False & lensClass .~ classy & classRequired .~ True & partialLenses .~ False & buildTraversals .~ True where classy :: String -> Maybe (String, String) classy n@(a:as) = Just ("Has" ++ n, toLower a:as) classy _ = Nothing -- | Build lenses (and traversals) with a sensible default configuration. -- -- /e.g./ -- -- @ -- data FooBar -- = Foo { _x, _y :: 'Int' } -- | Bar { _x :: 'Int' } -- 'makeLenses' ''FooBar -- @ -- -- will create -- -- @ -- x :: 'Lens'' FooBar 'Int' -- x f (Foo a b) = (\\a\' -> Foo a\' b) \<$\> f a -- x f (Bar a) = Bar \<$\> f a -- y :: 'Traversal'' FooBar 'Int' -- y f (Foo a b) = (\\b\' -> Foo a b\') \<$\> f b -- y _ c\@(Bar _) = pure c -- @ -- -- @ -- 'makeLenses' = 'makeLensesWith' 'lensRules' -- @ makeLenses :: Name -> Q [Dec] makeLenses = makeLensesWith lensRules -- | Make lenses and traversals for a type, and create a class when the -- type has no arguments. -- -- /e.g./ -- -- @ -- data Foo = Foo { _fooX, _fooY :: 'Int' } -- 'makeClassy' ''Foo -- @ -- -- will create -- -- @ -- class HasFoo t where -- foo :: 'Lens'' t Foo -- fooX :: 'Lens'' t 'Int' -- fooX = foo . go where go f (Foo x y) = (\\x\' -> Foo x' y) \<$\> f x -- fooY :: 'Lens'' t 'Int' -- fooY = foo . go where go f (Foo x y) = (\\y\' -> Foo x y') \<$\> f y -- instance HasFoo Foo where -- foo = id -- @ -- -- @ -- 'makeClassy' = 'makeLensesWith' 'classyRules' -- @ makeClassy :: Name -> Q [Dec] makeClassy = makeLensesWith classyRules -- | Make lenses and traversals for a type, and create a class when the type -- has no arguments. Works the same as 'makeClassy' except that (a) it -- expects that record field names do not begin with an underscore, (b) all -- record fields are made into lenses, and (c) the resulting lens is prefixed -- with an underscore. makeClassy_ :: Name -> Q [Dec] makeClassy_ = makeLensesWith classyRules_ -- | Derive lenses and traversals, specifying explicit pairings -- of @(fieldName, lensName)@. -- -- If you map multiple names to the same label, and it is present in the same -- constructor then this will generate a 'Traversal'. -- -- /e.g./ -- -- @ -- 'makeLensesFor' [(\"_foo\", \"fooLens\"), (\"baz\", \"lbaz\")] ''Foo -- 'makeLensesFor' [(\"_barX\", \"bar\"), (\"_barY\", \"bar\")] ''Bar -- @ makeLensesFor :: [(String, String)] -> Name -> Q [Dec] makeLensesFor fields = makeLensesWith $ lensRulesFor fields -- | Derive lenses and traversals, using a named wrapper class, and -- specifying explicit pairings of @(fieldName, traversalName)@. -- -- Example usage: -- -- @ -- 'makeClassyFor' \"HasFoo\" \"foo\" [(\"_foo\", \"fooLens\"), (\"bar\", \"lbar\")] ''Foo -- @ makeClassyFor :: String -> String -> [(String, String)] -> Name -> Q [Dec] makeClassyFor clsName funName fields = makeLensesWith $ classyRulesFor (const $ Just (clsName, funName)) fields -- | Build lenses with a custom configuration. makeLensesWith :: LensRules -> Name -> Q [Dec] makeLensesWith cfg nm = do inf <- reify nm case inf of TyConI decl -> makeLensesForDec cfg decl _ -> fail "makeLensesWith: Expected the name of a data type or newtype" -- | Generate a 'Prism' for each constructor of a data type. -- -- /e.g./ -- -- @ -- data FooBarBaz a -- = Foo Int -- | Bar a -- | Baz Int Char -- makePrisms ''FooBarBaz -- @ -- -- will create -- -- @ -- _Foo :: Prism' (FooBarBaz a) Int -- _Bar :: Prism (FooBarBaz a) (FooBarBaz b) a b -- _Baz :: Prism' (FooBarBaz a) (Int, Char) -- @ makePrisms :: Name -> Q [Dec] makePrisms nm = do inf <- reify nm case inf of TyConI decl -> makePrismsForDec decl _ -> fail "makePrisms: Expected the name of a data type or newtype" -- | Make lenses for all records in the given declaration quote. All record -- syntax in the input will be stripped off. -- -- /e.g./ -- -- @ -- declareLenses [d| -- data Foo = Foo { fooX, fooY :: 'Int' } -- deriving 'Show' -- |] -- @ -- -- will create -- -- @ -- data Foo = Foo 'Int' 'Int' deriving 'Show' -- fooX, fooY :: 'Lens'' Foo Int -- @ -- -- @ declareLenses = 'declareLensesWith' ('lensRules' '&' 'lensField' '.~' 'Just') @ declareLenses :: Q [Dec] -> Q [Dec] declareLenses = declareLensesWith (lensRules & lensField .~ Just) -- | Similar to 'makeLensesFor', but takes a declaration quote. declareLensesFor :: [(String, String)] -> Q [Dec] -> Q [Dec] declareLensesFor fields = declareLensesWith $ lensRulesFor fields & lensField .~ Just -- | For each record in the declaration quote, make lenses and traversals for -- it, and create a class when the type has no arguments. All record syntax -- in the input will be stripped off. -- -- /e.g./ -- -- @ -- declareClassy [d| -- data Foo = Foo { fooX, fooY :: 'Int' } -- deriving 'Show' -- |] -- @ -- -- will create -- -- @ -- data Foo = Foo 'Int' 'Int' deriving 'Show' -- class HasFoo t where -- foo :: 'Lens'' t Foo -- instance HasFoo Foo where foo = 'id' -- fooX, fooY :: HasFoo t => 'Lens'' t 'Int' -- @ -- -- @ declareClassy = 'declareLensesWith' ('classyRules' '&' 'lensField' '.~' 'Just') @ declareClassy :: Q [Dec] -> Q [Dec] declareClassy = declareLensesWith (classyRules & lensField .~ Just) -- | Similar to 'makeClassyFor', but takes a declaration quote. declareClassyFor :: [(String, (String, String))] -> [(String, String)] -> Q [Dec] -> Q [Dec] declareClassyFor classes fields = declareLensesWith $ classyRulesFor (`Prelude.lookup`classes) fields & lensField .~ Just -- | Generate a 'Prism' for each constructor of each data type. -- -- /e.g./ -- -- @ -- declarePrisms [d| -- data Exp = Lit Int | Var String | Lambda{ bound::String, body::Exp } -- |] -- @ -- -- will create -- -- @ -- data Exp = Lit Int | Var String | Lambda { bound::String, body::Exp } -- _Lit :: 'Prism'' Exp Int -- _Var :: 'Prism'' Exp String -- _Lambda :: 'Prism'' Exp (String, Exp) -- @ declarePrisms :: Q [Dec] -> Q [Dec] declarePrisms = declareWith $ \dec -> do emit =<< Trans.lift (makePrismsForDec dec) return dec -- | Build 'Wrapped' instance for each newtype. declareWrapped :: Q [Dec] -> Q [Dec] declareWrapped = declareWith $ \dec -> do maybeDecs <- Trans.lift (makeWrappedForDec dec) forM_ maybeDecs emit return dec -- | @ declareFields = 'declareFieldsWith' 'defaultFieldRules' @ declareFields :: Q [Dec] -> Q [Dec] declareFields = declareFieldsWith defaultFieldRules -- | Declare lenses for each records in the given declarations, using the -- specified 'LensRules'. Any record syntax in the input will be stripped -- off. declareLensesWith :: LensRules -> Q [Dec] -> Q [Dec] declareLensesWith rules = declareWith $ \dec -> do emit =<< Trans.lift (makeLensesForDec rules dec) return $ stripFields dec -- | Declare fields for each records in the given declarations, using the -- specified 'FieldRules'. Any record syntax in the input will be stripped -- off. declareFieldsWith :: FieldRules -> Q [Dec] -> Q [Dec] declareFieldsWith rules = declareWith $ \dec -> do emit =<< Trans.lift (makeFieldsForDec rules dec) return $ stripFields dec ----------------------------------------------------------------------------- -- Internal TH Implementation ----------------------------------------------------------------------------- -- | Transform @NewtypeD@s declarations to @DataD@s and @NewtypeInstD@s to -- @DataInstD@s. deNewtype :: Dec -> Dec deNewtype (NewtypeD ctx tyName args c d) = DataD ctx tyName args [c] d deNewtype (NewtypeInstD ctx tyName args c d) = DataInstD ctx tyName args [c] d deNewtype d = d makePrismsForDec :: Dec -> Q [Dec] makePrismsForDec decl = case makeDataDecl decl of Just dataDecl -> makePrismsForCons dataDecl _ -> fail "makePrisms: Unsupported data type" makePrismsForCons :: DataDecl -> Q [Dec] makePrismsForCons dataDecl@(DataDecl _ _ _ _ [_]) = case constructors dataDecl of -- Iso promotion via tuples [NormalC dataConName xs] -> makeIsoLenses rules dataDecl dataConName Nothing $ map (view _2) xs [RecC dataConName xs] -> makeIsoLenses rules dataDecl dataConName Nothing $ map (view _3) xs _ -> fail "makePrismsForCons: A single-constructor data type is required" where rules = defaultRules & handleSingletons .~ True & singletonRequired .~ True & singletonAndField .~ True & lensIso .~ (Just . ('_':)) makePrismsForCons dataDecl = concat <$> mapM (makePrismOrReviewForCon dataDecl canModifyTypeVar ) (constructors dataDecl) where conTypeVars = map (Set.fromList . toListOf typeVars) (constructors dataDecl) canModifyTypeVar = (`Set.member` typeVarsOnlyInOneCon) . view name typeVarsOnlyInOneCon = Set.fromList . concat . filter (\xs -> length xs == 1) . List.group . List.sort $ conTypeVars >>= toList onlyBuildReview :: Con -> Bool onlyBuildReview ForallC{} = True onlyBuildReview _ = False makePrismOrReviewForCon :: DataDecl -> (TyVarBndr -> Bool) -> Con -> Q [Dec] makePrismOrReviewForCon dataDecl canModifyTypeVar con | onlyBuildReview con = makeReviewForCon dataDecl con | otherwise = makePrismForCon dataDecl canModifyTypeVar con makeReviewForCon :: DataDecl -> Con -> Q [Dec] makeReviewForCon dataDecl con = do let functionName = mkName ('_': nameBase dataConName) (dataConName, fieldTypes) = ctrNameAndFieldTypes con sName <- newName "s" aName <- newName "a" fieldNames <- replicateM (length fieldTypes) (newName "x") -- Compute the type: Constructor Constraints => Review s (Type x y z) a fieldTypes let s = varT sName t = return (fullType dataDecl (map (VarT . view name) (dataParameters dataDecl))) a = varT aName b = toTupleT (map return fieldTypes) (conTyVars, conCxt) = case con of ForallC x y _ -> (x,y) _ -> ([],[]) functionType = forallT (map PlainTV [sName, aName] ++ conTyVars ++ dataParameters dataDecl) (return conCxt) (conT ''Review `appsT` [s,t,a,b]) -- Compute expression: unto (\(fields) -> Con fields) let pat = toTupleP (map varP fieldNames) lam = lam1E pat (conE dataConName `appsE1` map varE fieldNames) body = varE 'unto `appE` lam Prelude.sequence [ sigD functionName functionType , funD functionName [clause [] (normalB body) []] ] makePrismForCon :: DataDecl -> (TyVarBndr -> Bool) -> Con -> Q [Dec] makePrismForCon dataDecl canModifyTypeVar con = do remitterName <- newName "remitter" reviewerName <- newName "reviewer" xName <- newName "x" let resName = mkName $ '_': nameBase dataConName varNames <- for [0..length fieldTypes -1] $ \i -> newName ('x' : show i) let args = dataParameters dataDecl altArgsList <- forM (view name <$> filter isAltArg args) $ \arg -> (,) arg <$> newName (nameBase arg) let altArgs = Map.fromList altArgsList hitClause = clause [conP dataConName (fmap varP varNames)] (normalB $ appE (conE 'Right) $ toTupleE $ varE <$> varNames) [] otherCons = filter (/= con) (constructors dataDecl) missClauses | List.null otherCons = [] | Map.null altArgs = [clause [varP xName] (normalB (appE (conE 'Left) (varE xName))) []] | otherwise = reviewerIdClause <$> otherCons Prelude.sequence [ sigD resName . forallT (args ++ (PlainTV <$> Map.elems altArgs)) (return $ List.nub (dataContext dataDecl ++ substTypeVars altArgs (dataContext dataDecl))) $ if List.null altArgsList then conT ''Prism' `appsT` [ return $ fullType dataDecl $ VarT . view name <$> args , toTupleT $ pure <$> fieldTypes ] else conT ''Prism `appsT` [ return $ fullType dataDecl $ VarT . view name <$> args , return $ fullType dataDecl $ VarT . view name <$> substTypeVars altArgs args , toTupleT $ pure <$> fieldTypes , toTupleT $ pure <$> substTypeVars altArgs fieldTypes ] , funD resName [ clause [] (normalB (appsE [varE 'prism, varE remitterName, varE reviewerName])) [ funD remitterName [ clause [toTupleP (varP <$> varNames)] (normalB (conE dataConName `appsE1` fmap varE varNames)) [] ] , funD reviewerName $ hitClause : missClauses ] ] ] where (dataConName, fieldTypes) = ctrNameAndFieldTypes con conArgs = setOf typeVars fieldTypes isAltArg arg = canModifyTypeVar arg && conArgs^.contains(arg^.name) ctrNameAndFieldTypes :: Con -> (Name, [Type]) ctrNameAndFieldTypes (NormalC n ts) = (n, snd <$> ts) ctrNameAndFieldTypes (RecC n ts) = (n, view _3 <$> ts) ctrNameAndFieldTypes (InfixC l n r) = (n, [snd l, snd r]) ctrNameAndFieldTypes (ForallC _ _ c) = ctrNameAndFieldTypes c -- When a 'Prism' can change type variables it needs to pattern match on all -- other data constructors and rebuild the data so it will have the new type. reviewerIdClause :: Con -> ClauseQ reviewerIdClause con = do let (dataConName, fieldTypes) = ctrNameAndFieldTypes con varNames <- for [0 .. length fieldTypes - 1] $ \i -> newName ('x' : show i) clause [conP dataConName (fmap varP varNames)] (normalB (appE (conE 'Left) (conE dataConName `appsE1` fmap varE varNames))) [] -- | Given a set of names, build a map from those names to a set of fresh names -- based on them. freshMap :: Set Name -> Q (Map Name Name) freshMap ns = Map.fromList <$> for (toList ns) (\ n -> (,) n <$> newName (nameBase n)) -- i.e. AppT (AppT (TupleT 2) (ConT GHC.Types.Int)) (ConT GHC.Base.String) -- --> (\(x, y) -> Rect x y) makeIsoFrom :: Type -> Name -> Q ([Name], Exp) makeIsoFrom ty conName = lam <$> deCom ty where lam (ns, e) = (ns, LamE [TupP (map VarP ns)] e) deCom (TupleT _) = return ([], ConE conName) deCom (AppT l _) = do (ln, l') <- deCom l x <- newName "x" return (ln ++ [x], AppE l' (VarE x)) deCom t = fail $ "unable to create isomorphism for: " ++ show t -- i.e. AppT (AppT (TupleT 2) (ConT GHC.Types.Int)) (ConT GHC.Base.String) -- --> (\(Rect x y) -> (x, y)) makeIsoTo :: [Name] -> Name -> ExpQ makeIsoTo ns conName = lamE [conP conName (map varP ns)] $ tupE $ map varE ns makeIsoBody :: Name -> Exp -> Exp -> DecQ makeIsoBody lensName f t = funD lensName [clause [] (normalB body) []] where body = appsE [ varE 'iso , return f , return t ] makeLensBody :: Name -> Exp -> Exp -> DecQ makeLensBody lensName i o = do f <- newName "f" a <- newName "a" funD lensName [clause [] (normalB ( lamE [varP f, varP a] $ appsE [ varE 'fmap , return o , varE f `appE` (return i `appE` varE a) ])) []] plain :: TyVarBndr -> TyVarBndr plain (KindedTV t _) = PlainTV t plain (PlainTV t) = PlainTV t apps :: Type -> [Type] -> Type apps = Prelude.foldl AppT makeLensesForDec :: LensRules -> Dec -> Q [Dec] makeLensesForDec cfg decl = case makeDataDecl decl of Just dataDecl -> makeLensesForCons cfg dataDecl Nothing -> fail "makeLensesWith: Unsupported data type" makeLensesForCons :: LensRules -> DataDecl -> Q [Dec] makeLensesForCons cfg dataDecl = case constructors dataDecl of [NormalC dataConName [( _,ty)]] | cfg^.handleSingletons -> makeIsoLenses cfg dataDecl dataConName Nothing [ty] [RecC dataConName [(fld,_,ty)]] | cfg^.handleSingletons -> makeIsoLenses cfg dataDecl dataConName (Just fld) [ty] _ | cfg^.singletonRequired -> fail "makeLensesWith: A single-constructor single-argument data type is required" | otherwise -> makeFieldLenses cfg dataDecl makeDataDecl :: Dec -> Maybe DataDecl makeDataDecl dec = case deNewtype dec of DataD ctx tyName args cons _ -> Just DataDecl { dataContext = ctx , tyConName = Just tyName , dataParameters = args , fullType = apps $ ConT tyName , constructors = cons } DataInstD ctx familyName args cons _ -> Just DataDecl { dataContext = ctx , tyConName = Nothing , dataParameters = map PlainTV vars , fullType = \tys -> apps (ConT familyName) $ substType (Map.fromList $ zip vars tys) args , constructors = cons } where -- The list of "type parameters" to a data family instance is not -- explicitly specified in the source. Here we define it to be -- the set of distinct type variables that appear in the LHS. e.g. -- -- data instance F a Int (Maybe (a, b)) = G -- -- has 2 type parameters: a and b. vars = toList $ setOf typeVars args _ -> Nothing -- | A data, newtype, data instance or newtype instance declaration. data DataDecl = DataDecl { dataContext :: Cxt -- ^ Datatype context. , tyConName :: Maybe Name -- ^ Type constructor name, or Nothing for a data family instance. , dataParameters :: [TyVarBndr] -- ^ List of type parameters , fullType :: [Type] -> Type -- ^ Create a concrete record type given a substitution to -- 'detaParameters'. , constructors :: [Con] -- ^ Constructors -- , derivings :: [Name] -- currently not needed } makeIsoLenses :: LensRules -> DataDecl -> Name -> Maybe Name -> [Type] -> Q [Dec] makeIsoLenses cfg dataDecl dataConName maybeFieldName partTy = do let tyArgs = map plain (dataParameters dataDecl) m <- freshMap $ setOf typeVars tyArgs let aty = List.foldl' AppT (TupleT $ length partTy) partTy bty = substTypeVars m aty sty = fullType dataDecl $ map (VarT . view name) tyArgs tty = substTypeVars m sty quantified = ForallT (tyArgs ++ substTypeVars m tyArgs) (dataContext dataDecl ++ substTypeVars m (dataContext dataDecl)) maybeIsoName = mkName <$> view lensIso cfg (nameBase dataConName) lensOnly = not $ cfg^.singletonIso isoCon | lensOnly = ConT ''Lens | otherwise = ConT ''Iso isoCon' | lensOnly = ConT ''Lens' | otherwise = ConT ''Iso' makeBody | lensOnly = makeLensBody | otherwise = makeIsoBody isoDecls <- flip (maybe (return [])) maybeIsoName $ \isoName -> do let decl = SigD isoName $ quantified $ if cfg^.simpleLenses || Map.null m then isoCon' `apps` [sty,aty] else isoCon `apps` [sty,tty,aty,bty] (ns, f) <- makeIsoFrom aty dataConName t <- makeIsoTo ns dataConName body <- makeBody isoName t f #ifndef INLINING return $ if cfg^.generateSignatures then [decl, body] else [body] #else inlining <- inlinePragma isoName return $ if cfg^.generateSignatures then [decl, body, inlining] else [body, inlining] #endif accessorDecls <- case mkName <$> (maybeFieldName >>= view lensField cfg . nameBase) of jfn@(Just lensName) | (jfn /= maybeIsoName) && (isNothing maybeIsoName || cfg^.singletonAndField) -> do let decl = SigD lensName $ quantified $ if cfg^.simpleLenses || Map.null m then isoCon' `apps` [sty,aty] else isoCon `apps` [sty,tty,aty,bty] (ns, f) <- makeIsoFrom aty dataConName t <- makeIsoTo ns dataConName body <- makeBody lensName t f #ifndef INLINING return $ if cfg^.generateSignatures then [decl, body] else [body] #else inlining <- inlinePragma lensName return $ if cfg^.generateSignatures then [decl, body, inlining] else [body, inlining] #endif _ -> return [] return $ isoDecls ++ accessorDecls makeFieldGetterBody :: Bool -> Name -> [(Con, [Name])] -> Maybe Name -> Q Dec makeFieldGetterBody isFold lensName conList maybeMethodName = case maybeMethodName of Just methodName -> do go <- newName "go" let expr = infixApp (varE methodName) (varE '(Prelude..)) (varE go) funD lensName [ clause [] (normalB expr) [funD go clauses] ] Nothing -> funD lensName clauses where clauses = map buildClause conList buildClause (con, fields) | isRecord con = do f <- newName "_f" vars <- for (con^..conNamedFields._1) $ \fld -> if fld `List.elem` fields then Just <$> newName ('_':(nameBase fld++"")) else return Nothing let cpats = maybe wildP varP <$> vars -- Deconstruction fvals = map (appE (varE f) . varE) (catMaybes vars) -- Functor applications conName = con^.name fpat | List.null fvals = wildP | otherwise = varP f expr | not isFold && length fields /= 1 = appE (varE 'error) . litE . stringL $ show lensName ++ ": expected a single matching field in " ++ show conName ++ ", found " ++ show (length fields) | List.null fields = [| coerce (pure ()) |] | List.null fvals = [| coerce (pure ()) |] | otherwise = let add x y = [| $x *> $y |] in [| coerce $(List.foldl1 add fvals) |] clause [fpat, conP conName cpats] (normalB expr) [] -- Non-record are never the target of a generated field lens body buildClause (con, _fields) = -- clause: _ c@Con{} = expr -- expr: pure c clause [wildP, recP (con^.name) []] (normalB [| coerce (pure ()) |]) [] isRecord :: Con -> Bool isRecord RecC{} = True isRecord NormalC{} = False isRecord InfixC{} = False isRecord (ForallC _ _ c) = isRecord c makeFieldLensBody :: Bool -> Name -> [(Con, [Name])] -> Maybe Name -> Q Dec makeFieldLensBody isTraversal lensName conList maybeMethodName = case maybeMethodName of Just methodName -> do go <- newName "go" let expr = infixApp (varE methodName) (varE '(Prelude..)) (varE go) funD lensName [ clause [] (normalB expr) [funD go clauses] ] Nothing -> funD lensName clauses where clauses = map buildClause conList buildClause (con, fields) | isRecord con = do f <- newName "_f" vars <- for (con^..conNamedFields._1) $ \fld -> if fld `List.elem` fields then Left <$> ((,) <$> newName ('_':(nameBase fld++"'")) <*> newName ('_':nameBase fld)) else Right <$> newName ('_':nameBase fld) let cpats = map (varP . either fst id) vars -- Deconstruction cvals = map (varE . either snd id) vars -- Reconstruction fpats = map (varP . snd) $ lefts vars -- Lambda patterns fvals = map (appE (varE f) . varE . fst) $ lefts vars -- Functor applications conName = con^.name recon = conE conName `appsE1` cvals fpat | List.null fields = wildP | otherwise = varP f expr | not isTraversal && length fields /= 1 = appE (varE 'error) . litE . stringL $ show lensName ++ ": expected a single matching field in " ++ show conName ++ ", found " ++ show (length fields) | List.null fields = appE (varE 'pure) recon | otherwise = let step Nothing r = Just $ infixE (Just $ lamE fpats recon) (varE '(<$>)) (Just r) step (Just l) r = Just $ infixE (Just l) (varE '(<*>)) (Just r) in fromJust $ List.foldl step Nothing fvals -- = infixE (Just $ lamE fpats recon) (varE '(<$>)) $ Just $ List.foldl1 (\l r -> infixE (Just l) (varE '(<*>)) (Just r)) fvals clause [fpat, conP conName cpats] (normalB expr) [] -- Non-record are never the target of a generated field lens body buildClause (con, _fields) = do let fieldCount = lengthOf conFields con vars <- replicateM fieldCount (newName "x") let conName = con^.name expr | isTraversal = [| pure $(conE conName `appsE1` map varE vars) |] -- We must rebuild the value to support type changing | otherwise = [| error errorMsg |] where errorMsg = show lensName ++ ": non-record constructors require traversals to be generated" -- clause: _ c@Con{} = expr -- expr: pure c clause [wildP, conP conName (map varP vars)] (normalB expr) [] makeFieldLenses :: LensRules -> DataDecl -> Q [Dec] makeFieldLenses cfg dataDecl = do let tyArgs = map plain $ dataParameters dataDecl maybeLensClass = view lensClass cfg . nameBase =<< tyConName dataDecl maybeClassName = fmap (^._1.to mkName) maybeLensClass cons = constructors dataDecl t <- newName "t" a <- newName "a" --TODO: there's probably a more efficient way to do this. lensFields <- map (\xs -> (fst $ head xs, map snd xs)) . groupBy ((==) `on` fst) . sortBy (comparing fst) . concat <$> mapM (getLensFields $ view lensField cfg) cons -- varMultiSet knows how many usages of the type variables there are. let varMultiSet = List.concatMap (toListOf (conFields._2.typeVars)) cons varSet = Set.fromList $ map (view name) tyArgs bodies <- for lensFields $ \(lensName, fields) -> do let fieldTypes = map (view _3) fields -- All of the polymorphic variables not involved in these fields otherVars = varMultiSet List.\\ fieldTypes^..typeVars -- New type variable binders, and the type to represent the selected fields (tyArgs', cty) <- unifyTypes tyArgs fieldTypes -- Map for the polymorphic variables that are only involved in these fields, to new names for them. m <- freshMap . Set.difference varSet $ Set.fromList otherVars let aty | isJust maybeClassName = VarT t | otherwise = fullType dataDecl $ map (VarT . view name) tyArgs' bty = substTypeVars m aty dty = substTypeVars m cty s = setOf folded m relevantBndr b = s^.contains (b^.name) relevantCtx = not . Set.null . Set.intersection s . setOf typeVars tvs = tyArgs' ++ filter relevantBndr (substTypeVars m tyArgs') ctx = dataContext dataDecl ps = filter relevantCtx (substTypeVars m ctx) qs = case maybeClassName of #if MIN_VERSION_template_haskell(2,10,0) Just n | not (cfg^.createClass) -> AppT (ConT n) (VarT t) : (ctx ++ ps) #else Just n | not (cfg^.createClass) -> ClassP n [VarT t] : (ctx ++ ps) #endif | otherwise -> ps _ -> ctx ++ ps tvs' = case maybeClassName of Just _ | not (cfg^.createClass) -> PlainTV t : tvs | otherwise -> [] _ -> tvs --TODO: Better way to write this? fieldMap = fromListWith (++) $ map (\(cn,fn,_) -> (cn, [fn])) fields conList = map (\c -> (c, Map.findWithDefault [] (view name c) fieldMap)) cons maybeMethodName = fmap (mkName . view _2) maybeLensClass isTraversal <- do let notSingular = filter ((/= 1) . length . snd) conList showCon (c, fs) = pprint (c^.name) ++ " { " ++ intercalate ", " (map pprint fs) ++ " }" case (cfg^.buildTraversals, cfg^.partialLenses) of (True, True) -> fail "Cannot makeLensesWith both of the flags buildTraversals and partialLenses." (False, True) -> return False (True, False) | List.null notSingular -> return False | otherwise -> return True (False, False) | List.null notSingular -> return False | otherwise -> fail . unlines $ [ "Cannot use 'makeLensesWith' with constructors that don't map just one field" , "to a lens, without using either the buildTraversals or partialLenses flags." , if length conList == 1 then "The following constructor failed this criterion for the " ++ pprint lensName ++ " lens:" else "The following constructors failed this criterion for the " ++ pprint lensName ++ " lens:" ] ++ map showCon conList let decl = SigD lensName $ case cty of ForallT innerTys innerCxt cty' -> ForallT (tvs'++innerTys) (qs++innerCxt) $ apps (ConT (if isTraversal then ''Fold else ''Getter)) [aty,cty'] _ -> ForallT tvs' qs $ if aty == bty && cty == dty || cfg^.simpleLenses || isJust maybeClassName then apps (ConT (if isTraversal then ''Traversal' else ''Lens')) [aty,cty] else apps (ConT (if isTraversal then ''Traversal else ''Lens)) [aty,bty,cty,dty] body <- case cty of ForallT {} -> makeFieldGetterBody isTraversal lensName conList maybeMethodName _ -> makeFieldLensBody isTraversal lensName conList maybeMethodName #ifndef INLINING return $ if cfg^.generateSignatures then [decl, body] else [body] #else inlining <- inlinePragma lensName return $ if cfg^.generateSignatures then [decl, body, inlining] else [body, inlining] #endif let defs = Prelude.concat bodies case maybeLensClass of Nothing -> return defs Just (clsNameString, methodNameString) -> do let clsName = mkName clsNameString methodName = mkName methodNameString varArgs = varT . view name <$> tyArgs appliedCon = fullType dataDecl <$> sequenceA varArgs Prelude.sequence $ filter (\_ -> cfg^.createClass) [ classD (return []) clsName (PlainTV t : tyArgs) (if List.null tyArgs then [] else [FunDep [t] (view name <$> tyArgs)]) ( sigD methodName (appsT (conT ''Lens') [varT t, appliedCon]) : map return defs)] ++ filter (\_ -> cfg^.createInstance) [ instanceD (return []) ((conT clsName `appT` appliedCon) `appsT` varArgs) [ funD methodName [clause [varP a] (normalB (varE a)) []] #ifdef INLINING , inlinePragma methodName #endif ]] ++ filter (\_ -> not $ cfg^.createClass) (map return defs) -- | Gets @[(lens name, (constructor name, field name, type))]@ from a record constructor. getLensFields :: (String -> Maybe String) -> Con -> Q [(Name, (Name, Name, Type))] getLensFields f (RecC cn fs) = return . catMaybes $ fs <&> \(fn,_,t) -> f (nameBase fn) <&> \ln -> (mkName ln, (cn,fn,t)) getLensFields f (ForallC tvs cxts con) = fmap (filter p) (getLensFields f con) where -- Only select fields which do not mention existentially -- quantified type variables or variables mentioned in internal class constraints prohibitedTypes = tvs^..typeVars ++ cxts^..typeVars p field = not (any (\t -> elemOf (_2._3.typeVars) t field) prohibitedTypes) getLensFields _ _ = return [] -- TODO: properly fill this out -- -- Ideally this would unify the different field types, and figure out which polymorphic variables -- need to be the same. For now it just leaves them the same and yields the first type. -- (This leaves us open to inscrutable compile errors in the generated code) unifyTypes :: [TyVarBndr] -> [Type] -> Q ([TyVarBndr], Type) unifyTypes tvs tys = return (tvs, head tys) -- | Build 'Wrapped' instance for a given newtype makeWrapped :: Name -> DecsQ makeWrapped nm = do inf <- reify nm case inf of TyConI decl -> do maybeDecs <- makeWrappedForDec decl maybe (fail "makeWrapped: Unsupported data type") return maybeDecs _ -> fail "makeWrapped: Expected the name of a newtype or datatype" makeWrappedForDec :: Dec -> Q (Maybe [Dec]) makeWrappedForDec decl = case makeDataDecl decl of Just dataDecl | [con] <- constructors dataDecl , [field] <- toListOf (conFields._2) con -> do wrapped <- makeWrappedInstance dataDecl con field rewrapped <- makeRewrappedInstance dataDecl return (Just [rewrapped, wrapped]) _ -> return Nothing makeRewrappedInstance :: DataDecl -> DecQ makeRewrappedInstance dataDecl = do t <- varT <$> newName "t" let typeArgs = map (view name) (dataParameters dataDecl) typeArgs' <- do m <- freshMap (Set.fromList typeArgs) return (substTypeVars m typeArgs) -- Con a b c... let appliedType = return (fullType dataDecl (map VarT typeArgs)) -- Con a' b' c'... appliedType' = return (fullType dataDecl (map VarT typeArgs')) -- Con a' b' c'... ~ t #if MIN_VERSION_template_haskell(2,10,0) eq = AppT. AppT EqualityT <$> appliedType' <*> t #else eq = equalP appliedType' t #endif -- Rewrapped (Con a b c...) t klass = conT ''Rewrapped `appsT` [appliedType, t] -- instance (Con a' b' c'... ~ t) => Rewrapped (Con a b c...) t instanceD (cxt [eq]) klass [] makeWrappedInstance :: DataDecl-> Con -> Type -> DecQ makeWrappedInstance dataDecl con fieldType = do let conName = view name con let typeArgs = toListOf typeVars (dataParameters dataDecl) -- Con a b c... let appliedType = fullType dataDecl (map VarT typeArgs) -- type Unwrapped (Con a b c...) = $fieldType let unwrappedATF = tySynInstD' ''Unwrapped [return appliedType] (return fieldType) -- Wrapped (Con a b c...) let klass = conT ''Wrapped `appT` return appliedType -- _Wrapped' = iso (\(Con x) -> x) Con let wrapFun = conE conName let unwrapFun = newName "x" >>= \x -> lam1E (conP conName [varP x]) (varE x) let isoMethod = funD '_Wrapped' [clause [] (normalB [|iso $unwrapFun $wrapFun|]) []] -- instance Wrapped (Con a b c...) where -- type Unwrapped (Con a b c...) = fieldType -- _Wrapped' = iso (\(Con x) -> x) Con instanceD (cxt []) klass [unwrappedATF, isoMethod] #if !(MIN_VERSION_template_haskell(2,7,0)) -- | The orphan instance for old versions is bad, but programming without 'Applicative' is worse. instance Applicative Q where pure = return (<*>) = ap #endif #ifdef INLINING inlinePragma :: Name -> Q Dec #if MIN_VERSION_template_haskell(2,8,0) # ifdef OLD_INLINE_PRAGMAS -- 7.6rc1? inlinePragma methodName = pragInlD methodName $ inlineSpecNoPhase Inline False # else -- 7.7.20120830 inlinePragma methodName = pragInlD methodName Inline FunLike AllPhases # endif #else -- GHC <7.6, TH <2.8.0 inlinePragma methodName = pragInlD methodName $ inlineSpecNoPhase True False #endif #endif data FieldRules = FieldRules { _getPrefix :: [String] -> String -> Maybe String , _rawLensNaming :: String -> String , _niceLensNaming :: String -> Maybe String , _classNaming :: String -> Maybe String } data Field = Field { _fieldName :: Name , _fieldLensPrefix :: String , _fieldLensName :: Name , _fieldClassName :: Name , _fieldClassLensName :: Name , _fieldNameType :: Type } overHead :: (a -> a) -> [a] -> [a] overHead _ [] = [] overHead f (x:xs) = f x : xs -- | Field rules for fields in the form @ _prefix_fieldname @ underscoreFields :: FieldRules underscoreFields = FieldRules prefix rawLens niceLens classNaming where prefix _ ('_':xs) | '_' `List.elem` xs = Just (takeWhile (/= '_') xs) prefix _ _ = Nothing rawLens x = x ++ "_lens" niceLens x = prefix [] x <&> \n -> drop (length n + 2) x classNaming x = niceLens x <&> ("Has_" ++) -- | Field rules for fields in the form @ prefixFieldname or _prefixFieldname @ -- If you want all fields to be lensed, then there is no reason to use an @_@ before the prefix. -- If any of the record fields leads with an @_@ then it is assume a field without an @_@ should not have a lens created. camelCaseFields :: FieldRules camelCaseFields = FieldRules prefix rawLens niceLens classNaming where sepUpper x = case break isUpper x of (p, s) | List.null p || List.null s -> Nothing | otherwise -> Just (p,s) prefix fields = fmap fst . sepUpper <=< dealWith_ fields rawLens x = x ++ "Lens" niceLens x = overHead toLower . snd <$> sepUpper x classNaming x = niceLens x <&> \ (n:ns) -> "Has" ++ toUpper n : ns dealWith_ :: [String] -> String -> Maybe String dealWith_ fields field | not $ any (fst . leading_) fields = Just field | otherwise = if leading then Just trailing else Nothing where leading_ ('_':xs) = (True, xs) leading_ xs = (False, xs) (leading, trailing) = leading_ field collectRecords :: [Con] -> [VarStrictType] collectRecords cons = nubBy varEq allRecordFields where varEq (name1,_,_) (name2,_,_) = name1 == name2 allRecordFields = [ field | RecC _ fields <- cons , field <- fields ] verboseLenses :: FieldRules -> Dec -> Q [Dec] verboseLenses c decl = do cons <- case deNewtype decl of DataD _ _ _ cons _ -> return cons DataInstD _ _ _ cons _ -> return cons _ -> fail "verboseLenses: Unsupported data type" let rs = collectRecords cons if List.null rs then fail "verboseLenses: Expected the name of a record type" else flip makeLenses' decl $ mkFields c rs & map (\(Field n _ l _ _ _) -> (show n, show l)) where makeLenses' fields' = makeLensesForDec $ lensRules & lensField .~ (`Prelude.lookup` fields') & buildTraversals .~ False & partialLenses .~ True mkFields :: FieldRules -> [VarStrictType] -> [Field] mkFields (FieldRules prefix' raw' nice' clas') rs = Maybe.mapMaybe namer fieldNamesAndTypes & List.groupBy (on (==) _fieldLensPrefix) & (\ gs -> case gs of x:_ -> x _ -> []) where fieldNamesAndTypes = [(nameBase n, t) | (n,_,t) <- rs] fieldNames = map fst fieldNamesAndTypes namer (field, fieldType) = do let rawlens = mkName (raw' field) prefix <- prefix' fieldNames field nice <- mkName <$> nice' field clas <- mkName <$> clas' field return (Field (mkName field) prefix rawlens clas nice fieldType) hasClassAndInstance :: FieldRules -> Dec -> Q [Dec] hasClassAndInstance cfg decl = do c <- newName "c" e <- newName "e" dataDecl <- case makeDataDecl decl of Just dataDecl -> return dataDecl _ -> fail "hasClassAndInstance: Unsupported data type" let rs = collectRecords $ constructors dataDecl when (List.null rs) $ fail "hasClassAndInstance: Expected the name of a record type" fmap concat . forM (mkFields cfg rs) $ \(Field _ _ fullLensName className lensName fieldType) -> do classHas <- classD (return []) className [ PlainTV c, PlainTV e ] [ FunDep [c] [e] ] [ sigD lensName (conT ''Lens' `appsT` [varT c, varT e])] instanceHas <- instanceD (return []) (return $ ConT className `apps` [fullType dataDecl $ map (VarT . view name) (dataParameters dataDecl) , fieldType]) [ #ifdef INLINING inlinePragma lensName, #endif funD lensName [ clause [] (normalB (varE fullLensName)) [] ] ] classAlreadyExists <- isJust `fmap` lookupTypeName (show className) return (if classAlreadyExists then [instanceHas] else [classHas, instanceHas]) -- | Make fields with the specified 'FieldRules'. makeFieldsWith :: FieldRules -> Name -> Q [Dec] makeFieldsWith c n = do inf <- reify n case inf of TyConI decl -> makeFieldsForDec c decl _ -> fail "makeFieldsWith: Expected the name of a data type or newtype" makeFieldsForDec :: FieldRules -> Dec -> Q [Dec] makeFieldsForDec cfg decl = liftA2 (++) (verboseLenses cfg decl) (hasClassAndInstance cfg decl) -- | Generate overloaded field accessors. -- -- /e.g/ -- -- @ -- data Foo a = Foo { _fooX :: 'Int', _fooY : a } -- newtype Bar = Bar { _barX :: 'Char' } -- makeFields ''Foo -- makeFields ''Bar -- @ -- -- will create -- -- @ -- _fooXLens :: Lens' (Foo a) Int -- _fooYLens :: Lens (Foo a) (Foo b) a b -- class HasX s a | s -> a where -- x :: Lens' s a -- instance HasX (Foo a) Int where -- x = _fooXLens -- class HasY s a | s -> a where -- y :: Lens' s a -- instance HasY (Foo a) a where -- y = _fooYLens -- _barXLens :: Iso' Bar Char -- instance HasX Bar Char where -- x = _barXLens -- @ -- -- @ -- makeFields = 'makeFieldsWith' 'defaultFieldRules' -- @ makeFields :: Name -> Q [Dec] makeFields = makeFieldsWith defaultFieldRules -- | @ defaultFieldRules = 'camelCaseFields' @ defaultFieldRules :: FieldRules defaultFieldRules = camelCaseFields -- Declaration quote stuff declareWith :: (Dec -> Declare Dec) -> Q [Dec] -> Q [Dec] declareWith fun = (runDeclare . traverseDataAndNewtype fun =<<) -- | Monad for emitting top-level declarations as a side effect. type Declare = WriterT (Endo [Dec]) Q runDeclare :: Declare [Dec] -> Q [Dec] runDeclare dec = do (out, endo) <- runWriterT dec return $ out ++ appEndo endo [] emit :: [Dec] -> Declare () emit decs = tell $ Endo (decs++) -- | Traverse each data, newtype, data instance or newtype instance -- declaration. traverseDataAndNewtype :: (Applicative f) => (Dec -> f Dec) -> [Dec] -> f [Dec] traverseDataAndNewtype f decs = traverse go decs where go dec = case dec of DataD{} -> f dec NewtypeD{} -> f dec DataInstD{} -> f dec NewtypeInstD{} -> f dec -- Recurse into instance declarations because they main contain -- associated data family instances. InstanceD ctx inst body -> InstanceD ctx inst <$> traverse go body _ -> pure dec stripFields :: Dec -> Dec stripFields dec = case dec of DataD ctx tyName tyArgs cons derivings -> DataD ctx tyName tyArgs (map deRecord cons) derivings NewtypeD ctx tyName tyArgs con derivings -> NewtypeD ctx tyName tyArgs (deRecord con) derivings DataInstD ctx tyName tyArgs cons derivings -> DataInstD ctx tyName tyArgs (map deRecord cons) derivings NewtypeInstD ctx tyName tyArgs con derivings -> NewtypeInstD ctx tyName tyArgs (deRecord con) derivings _ -> dec deRecord :: Con -> Con deRecord con@NormalC{} = con deRecord con@InfixC{} = con deRecord (ForallC tyVars ctx con) = ForallC tyVars ctx $ deRecord con deRecord (RecC conName fields) = NormalC conName (map dropFieldName fields) where dropFieldName (_, str, typ) = (str, typ)