{-# LANGUAGE CPP #-} {-# 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) 2012-13 Edward Kmett, Michael Sloan -- License : BSD-style (see the file LICENSE) -- Maintainer : Edward Kmett -- Stability : experimental -- Portability : non-portable -- ----------------------------------------------------------------------------- module Control.Lens.TH ( -- * Constructing Lenses Automatically makeLenses, makeLensesFor , makeClassy, makeClassyFor , makeIso , makePrisms , makeWrapped , makeFields -- * Configuring Lenses , makeLensesWith , makeFieldsWith , defaultRules , defaultFieldRules , camelCaseFields , underscoreFields , LensRules(LensRules) , FieldRules(FieldRules) , lensRules , classyRules , isoRules , lensIso , lensField , lensClass , lensFlags , LensFlag(..) , simpleLenses , partialLenses , buildTraversals , handleSingletons , singletonIso , singletonRequired , createClass , createInstance , classRequired , singletonAndField , generateSignatures ) where import Control.Applicative #if !(MIN_VERSION_template_haskell(2,7,0)) import Control.Monad (ap) #endif import Control.Lens.At import Control.Lens.Combinators import Control.Lens.Fold import Control.Lens.Getter import Control.Lens.Iso import Control.Lens.Lens import Control.Lens.Prism import Control.Lens.Setter import Control.Lens.Tuple import Control.Lens.Traversal import Control.Lens.Wrapped import Data.Char (toLower, toUpper, isUpper) import Data.Either (lefts) import Data.Foldable hiding (concat) 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.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 {-# ANN module "HLint: ignore Use foldl" #-} -- | 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 -- | 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 -- | Rules for making an isomorphism from a data type. isoRules :: LensRules isoRules = defaultRules & handleSingletons .~ True & singletonRequired .~ True & singletonAndField .~ True -- | Build lenses (and traversals) with a sensible default configuration. -- -- @ -- '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 :: 'Control.Lens.Type.Simple' 'Lens' t Foo -- instance HasFoo Foo where foo = 'id' -- fooX, fooY :: HasFoo t => 'Control.Lens.Type.Simple' 'Lens' t 'Int' -- @ -- -- @ -- 'makeClassy' = 'makeLensesWith' 'classyRules' -- @ makeClassy :: Name -> Q [Dec] makeClassy = makeLensesWith classyRules -- | Make a top level isomorphism injecting /into/ the type. -- -- The supplied name is required to be for a type with a single constructor -- that has a single argument. -- -- /e.g./ -- -- @ -- newtype 'List' a = 'List' [a] -- 'makeIso' ''List -- @ -- -- will create -- -- @ -- 'list' :: 'Iso' [a] [b] ('List' a) ('List' b) -- @ -- -- @ -- 'makeIso' = 'makeLensesWith' 'isoRules' -- @ makeIso :: Name -> Q [Dec] makeIso = makeLensesWith isoRules -- | 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 $ lensRules & lensField .~ (`Prelude.lookup` 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 $ classyRules & lensClass .~ const (Just (clsName,funName)) & lensField .~ (`Prelude.lookup` fields) -- | Build lenses with a custom configuration. makeLensesWith :: LensRules -> Name -> Q [Dec] makeLensesWith cfg nm = do inf <- reify nm case inf of TyConI decl -> case deNewtype decl of DataD ctx tyConName args cons _ -> case cons of [NormalC dataConName [( _,ty)]] | cfg^.handleSingletons -> makeIsoLenses cfg ctx tyConName args dataConName Nothing ty [RecC dataConName [(fld,_,ty)]] | cfg^.handleSingletons -> makeIsoLenses cfg ctx tyConName args dataConName (Just fld) ty _ | cfg^.singletonRequired -> fail "makeLensesWith: A single-constructor single-argument data type is required" | otherwise -> makeFieldLenses cfg ctx tyConName args cons _ -> fail "makeLensesWith: Unsupported data type" _ -> fail "makeLensesWith: Expected the name of a data type or newtype" -- | Generate a 'Prism' for each constructor of a data type. makePrisms :: Name -> Q [Dec] makePrisms nm = do inf <- reify nm case inf of TyConI decl -> case deNewtype decl of DataD ctx tyConName args cons _ -> makePrismsForCons ctx tyConName args cons _ -> fail "makePrisms: Unsupported data type" _ -> fail "makePrisms: Expected the name of a data type or newtype" ----------------------------------------------------------------------------- -- Internal TH Implementation ----------------------------------------------------------------------------- -- | Transform @NewtypeD@s declarations to @DataD@s. deNewtype :: Dec -> Dec deNewtype (NewtypeD ctx tyConName args c d) = DataD ctx tyConName args [c] d deNewtype d = d makePrismsForCons :: [Pred] -> Name -> [TyVarBndr] -> [Con] -> Q [Dec] makePrismsForCons ctx tyConName args cons = concat <$> mapM (makePrismForCon ctx tyConName args canModifyTypeVar cons) cons where conTypeVars = map (Set.fromList . toListOf typeVars) cons canModifyTypeVar = (`Set.member` typeVarsOnlyInOneCon) . view name typeVarsOnlyInOneCon = Set.fromList . concat . filter (\xs -> length xs == 1) . List.group . List.sort $ conTypeVars >>= toList makePrismForCon :: [Pred] -> Name -> [TyVarBndr] -> (TyVarBndr -> Bool) -> [Con] -> Con -> Q [Dec] makePrismForCon ctx tyConName args canModifyTypeVar allCons 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) 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 <$> varNames) [] otherCons = filter (/= con) allCons missClauses | List.null otherCons = [] | Map.null altArgs = [clause [varP xName] (normalB (appE (conE 'Left) (varE xName))) []] | otherwise = reviewerIdClause <$> otherCons Prelude.sequence [ sigD resName . forallT (args ++ (PlainTV <$> Map.elems altArgs)) (return $ List.nub (ctx ++ substTypeVars altArgs ctx)) $ if altArgsList == [] then conT ''Prism' `appsT` [ appsT (conT tyConName) $ varT . view name <$> args , toTupleT $ pure <$> fieldTypes ] else conT ''Prism `appsT` [ appsT (conT tyConName) $ varT . view name <$> args , appsT (conT tyConName) $ 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 (appsE (conE dataConName : 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) $ appsE (conE dataConName : fmap varE varNames)) [] toTupleT :: [TypeQ] -> TypeQ toTupleT [x] = x toTupleT xs = appsT (tupleT (length xs)) xs toTupleE :: [ExpQ] -> ExpQ toTupleE [x] = x toTupleE xs = tupE xs toTupleP :: [PatQ] -> PatQ toTupleP [x] = x toTupleP xs = tupP xs -- | 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)) makeIsoTo :: Name -> ExpQ makeIsoTo = conE makeIsoFrom :: Name -> ExpQ makeIsoFrom conName = do b <- newName "b" lamE [conP conName [varP b]] $ varE b makeIsoBody :: Name -> Name -> (Name -> ExpQ) -> (Name -> ExpQ) -> DecQ makeIsoBody lensName conName f g = funD lensName [clause [] (normalB body) []] where body = appsE [ varE 'iso , g conName , f conName ] makeLensBody :: Name -> Name -> (Name -> ExpQ) -> (Name -> ExpQ) -> DecQ makeLensBody lensName conName i o = do f <- newName "f" a <- newName "a" funD lensName [clause [] (normalB ( lamE [varP f, varP a] $ appsE [ varE 'fmap , o conName , varE f `appE` (i conName `appE` varE a) ])) []] plain :: TyVarBndr -> TyVarBndr plain (KindedTV t _) = PlainTV t plain (PlainTV t) = PlainTV t appArgs :: Type -> [TyVarBndr] -> Type appArgs t [] = t appArgs t (x:xs) = appArgs (AppT t (VarT (x^.name))) xs apps :: Type -> [Type] -> Type apps = Prelude.foldl AppT appsT :: TypeQ -> [TypeQ] -> TypeQ appsT = Prelude.foldl appT makeIsoLenses :: LensRules -> Cxt -> Name -> [TyVarBndr] -> Name -> Maybe Name -> Type -> Q [Dec] makeIsoLenses cfg ctx tyConName tyArgs0 dataConName maybeFieldName partTy = do let tyArgs = map plain tyArgs0 m <- freshMap $ setOf typeVars tyArgs let aty = partTy bty = substTypeVars m aty cty = appArgs (ConT tyConName) tyArgs dty = substTypeVars m cty quantified = ForallT (tyArgs ++ substTypeVars m tyArgs) (ctx ++ substTypeVars m ctx) 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` [aty,cty] else isoCon `apps` [aty,bty,cty,dty] body <- makeBody isoName dataConName makeIsoFrom makeIsoTo #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` [cty,aty] else isoCon `apps` [cty,dty,aty,bty] body <- makeBody lensName dataConName makeIsoTo makeIsoFrom #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 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) = 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 = appsE $ conE conName : cvals 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 [varP f, conP conName cpats] (normalB expr) [] makeFieldLenses :: LensRules -> Cxt -- ^ surrounding cxt driven by the data type context -> Name -- ^ data/newtype constructor name -> [TyVarBndr] -- ^ args -> [Con] -> Q [Dec] makeFieldLenses cfg ctx tyConName tyArgs0 cons = do let tyArgs = map plain tyArgs0 maybeLensClass = view lensClass cfg $ nameBase tyConName maybeClassName = fmap (^._1.to mkName) maybeLensClass 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 = appArgs (ConT tyConName) 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') ps = filter relevantCtx (substTypeVars m ctx) qs = case maybeClassName of Just n | not (cfg^.createClass) -> ClassP n [VarT t] : (ctx ++ ps) | 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 $ ForallT tvs' qs vars where vars | aty == bty && cty == dty || cfg^.simpleLenses || isJust maybeClassName = apps (ConT (if isTraversal then ''Traversal' else ''Lens')) [aty,cty] | otherwise = apps (ConT (if isTraversal then ''Traversal else ''Lens)) [aty,bty,cty,dty] body <- 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 = conT tyConName `appsT` 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 _ _ = 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 -> case deNewtype decl of DataD _ tyConName args [con] _ -> makeWrappedInstance tyConName args con _ -> fail "makeWrapped: Unsupported data type" _ -> fail "makeWrapped: Expected the name of a newtype or datatype" makeWrappedInstance :: Name -> [TyVarBndr] -> Con -> DecsQ makeWrappedInstance tyConName tyArgs con = do let tyNames = view name <$> tyArgs tyNameRemap <- makeNameRemap tyNames (newtypeConName, fieldType) <- case ctrNameAndFieldTypes con of (a,[b]) -> return (a,b) _ -> fail "makeWrappedInstance: Constructor must have a single field" let outer1 = conT tyConName `appsT` fmap varT tyNames inner1 = return fieldType outer2 = conT tyConName `appsT` fmap (varT . snd) tyNameRemap inner2 = return $ substTypeVars (Map.fromList tyNameRemap) fieldType dec <- instanceD (cxt []) (conT ''Wrapped `appsT` [inner1, inner2, outer1, outer2]) [makeIsoBody 'wrapped newtypeConName makeIsoFrom makeIsoTo] return [dec] where -- Return list to preserve order, convert to Map later makeNameRemap tyNames = for tyNames $ \ tyName -> do tyName1 <- newName (show tyName) return (tyName, tyName1) #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 -> 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 } 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 @ camelCaseFields :: FieldRules camelCaseFields = FieldRules prefix rawLens niceLens classNaming where sep x = case break isUpper x of (p, s) | List.null p || List.null s -> Nothing | otherwise -> Just (p,s) prefix x = do ('_':xs,_) <- sep x; return xs rawLens x = x ++ "Lens" niceLens x = overHead toLower . snd <$> sep x classNaming x = niceLens x <&> \ (n:ns) -> "Has" ++ toUpper n : ns collectRecords :: [Con] -> [VarStrictType] collectRecords cons = rs where recs = filter (\r -> case r of RecC{} -> True; _ -> False) cons rs' = List.concatMap (\(RecC _ _rs) -> _rs) recs rs = nubBy ((==) `on` (^._1)) rs' verboseLenses :: FieldRules -> Name -> Q [Dec] verboseLenses c src = do rs <- do inf <- reify src case inf of TyConI decl -> case deNewtype decl of DataD _ _ _ cons _ -> do let rs = collectRecords cons if List.null rs then fail "verboseLenses: Expected the name of a record type" else return rs _ -> fail "verboseLenses: Unsupported data type" _ -> fail "verboseLenses: Expected the name of a data type or newtype" flip makeLenses' src $ mkFields c rs & map (\(Field n _ l _ _) -> (show n, show l)) where makeLenses' fields' = makeLensesWith $ lensRules & lensField .~ (`Prelude.lookup` fields') & buildTraversals .~ False & partialLenses .~ True mkFields :: FieldRules -> [VarStrictType] -> [Field] mkFields (FieldRules prefix' raw' nice' clas') rs = Maybe.mapMaybe namer rs & List.groupBy (on (==) _fieldLensPrefix) & (\ gs -> case gs of x:_ -> x _ -> []) where namer (n', _, _) = do let field = nameBase n' rawlens = mkName (raw' field) prefix <- prefix' field nice <- mkName <$> nice' field clas <- mkName <$> clas' field return (Field (mkName field) prefix rawlens clas nice) hasClassAndInstance :: FieldRules -> Name -> Q [Dec] hasClassAndInstance cfg src = do c <- newName "c" e <- newName "e" (vs,rs) <- do inf <- reify src case inf of TyConI decl -> case deNewtype decl of DataD _ _ vs cons _ -> do let rs = collectRecords cons if List.null rs then fail "hasClassAndInstance: Expected the name of a record type" else return (vs,rs) _ -> fail "hasClassAndInstance: Unsupported data type" _ -> fail "hasClassAndInstance: Expected the name of a data type or newtype" fmap concat . forM (mkFields cfg rs) $ \(Field field _ fullLensName className lensName) -> do classHas <- classD (return []) className [ PlainTV c, PlainTV e ] [ FunDep [c] [e] ] [ sigD lensName (conT ''Lens' `appsT` [varT c, varT e])] fieldType <- do VarI _ t _ _ <- reify field case t of AppT _ fieldType -> return fieldType ForallT _ [] (AppT _ fieldType) -> return fieldType _ -> error "Cannot get fieldType" instanceHas <- instanceD (return []) (conT className `appsT` [conT src `appsT` map (varT.view name) vs, return fieldType]) [ #ifdef INLINING inlinePragma lensName, #endif funD lensName [ clause [] (normalB (global 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 = liftA2 (++) (verboseLenses c n) (hasClassAndInstance c n) -- | @ makeFields = 'makeFieldsWith' 'defaultFieldRules' @ makeFields :: Name -> Q [Dec] makeFields = makeFieldsWith defaultFieldRules -- | @ defaultFieldRules = 'camelCaseFields' @ defaultFieldRules :: FieldRules defaultFieldRules = camelCaseFields