{-# LANGUAGE CPP #-} {-# LANGUAGE PatternGuards #-} #ifdef TRUSTWORTHY # if MIN_VERSION_template_haskell(2,12,0) {-# LANGUAGE Safe #-} # else {-# LANGUAGE Trustworthy #-} # endif #endif #ifndef MIN_VERSION_base #define MIN_VERSION_base(x,y,z) 1 #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) 2012-16 Edward Kmett, 2012-13 Michael Sloan -- License : BSD-style (see the file LICENSE) -- Maintainer : Edward Kmett -- Stability : experimental -- Portability : non-portable -- ----------------------------------------------------------------------------- module Control.Lens.TH ( -- * Constructing Lenses Automatically -- ** Lenses for data fields makeLenses, makeLensesFor , makeClassy, makeClassyFor, makeClassy_ , makeFields , makeFieldsNoPrefix -- ** Prisms , makePrisms , makeClassyPrisms -- ** Wrapped , makeWrapped -- * Constructing Lenses Given a Declaration Quote -- ** Lenses for data fields , declareLenses, declareLensesFor , declareClassy, declareClassyFor , declareFields -- ** Prisms , declarePrisms -- ** Wrapped , declareWrapped -- * Configuring Lenses -- ** Running LensRules , makeLensesWith , declareLensesWith -- ** LensRules type , LensRules -- ** Predefined LensRules , lensRules , lensRulesFor , classyRules , classyRules_ , defaultFieldRules , camelCaseFields , classUnderscoreNoPrefixFields , underscoreFields , abbreviatedFields -- ** LensRules configuration accessors , lensField , FieldNamer , DefName(..) , lensClass , ClassyNamer , simpleLenses , createClass , generateSignatures , generateUpdateableOptics , generateLazyPatterns -- ** FieldNamers , underscoreNoPrefixNamer , lookingupNamer , mappingNamer , camelCaseNamer , classUnderscoreNoPrefixNamer , underscoreNamer , abbreviatedNamer ) where #if !MIN_VERSION_base(4,8,0) import Control.Applicative #endif #if !(MIN_VERSION_template_haskell(2,7,0)) import Control.Monad (ap) #endif import Control.Monad.Trans.Class import Control.Monad.Trans.State import Control.Monad.Trans.Writer import Control.Lens.Fold import Control.Lens.Getter import Control.Lens.Lens import Control.Lens.Setter import Control.Lens.Tuple import Control.Lens.Traversal import Control.Lens.Internal.TH import Control.Lens.Internal.FieldTH import Control.Lens.Internal.PrismTH import Control.Lens.Wrapped () -- haddocks import Control.Lens.Type () -- haddocks import Data.Char (toLower, toUpper, isUpper) import Data.Foldable hiding (concat, any) import Data.List as List import qualified Data.Map as Map import Data.Map (Map) import Data.Maybe (maybeToList) import Data.Monoid import qualified Data.Set as Set import Data.Set (Set) import Data.Set.Lens import Data.Traversable hiding (mapM) import Language.Haskell.TH import Language.Haskell.TH.Lens import Language.Haskell.TH.Syntax hiding (lift) #ifdef HLINT {-# ANN module "HLint: ignore Eta reduce" #-} {-# ANN module "HLint: ignore Use fewer imports" #-} {-# ANN module "HLint: ignore Use foldl" #-} #endif -- | Generate "simple" optics even when type-changing optics are possible. -- (e.g. 'Lens'' instead of 'Lens') simpleLenses :: Lens' LensRules Bool simpleLenses f r = fmap (\x -> r { _simpleLenses = x}) (f (_simpleLenses r)) -- | 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 f r = fmap (\x -> r { _generateSigs = x}) (f (_generateSigs r)) -- | Generate "updateable" optics when 'True'. When 'False', 'Fold's will be -- generated instead of 'Traversal's and 'Getter's will be generated instead -- of 'Lens'es. This mode is intended to be used for types with invariants -- which must be maintained by "smart" constructors. generateUpdateableOptics :: Lens' LensRules Bool generateUpdateableOptics f r = fmap (\x -> r { _allowUpdates = x}) (f (_allowUpdates r)) -- | Generate optics using lazy pattern matches. This can -- allow fields of an undefined value to be initialized with lenses: -- -- @ -- data Foo = Foo {_x :: Int, _y :: Bool} -- deriving Show -- -- 'makeLensesWith' ('lensRules' & 'generateLazyPatterns' .~ True) ''Foo -- @ -- -- @ -- > undefined & x .~ 8 & y .~ True -- Foo {_x = 8, _y = True} -- @ -- -- The downside of this flag is that it can lead to space-leaks and -- code-size/compile-time increases when generated for large records. By -- default this flag is turned off, and strict optics are generated. -- -- When using lazy optics the strict optic can be recovered by composing -- with '$!': -- -- @ -- strictOptic = ($!) . lazyOptic -- @ generateLazyPatterns :: Lens' LensRules Bool generateLazyPatterns f r = fmap (\x -> r { _lazyPatterns = x}) (f (_lazyPatterns r)) -- | Create the class if the constructor is 'Control.Lens.Type.Simple' and the -- 'lensClass' rule matches. createClass :: Lens' LensRules Bool createClass f r = fmap (\x -> r { _generateClasses = x}) (f (_generateClasses r)) -- | 'Lens'' to access the convention for naming fields in our 'LensRules'. lensField :: Lens' LensRules FieldNamer lensField f r = fmap (\x -> r { _fieldToDef = x}) (f (_fieldToDef r)) -- | 'Lens'' to access the option for naming "classy" lenses. lensClass :: Lens' LensRules ClassyNamer lensClass f r = fmap (\x -> r { _classyLenses = x }) (f (_classyLenses r)) -- | Rules for making fairly simple partial lenses, ignoring the special cases -- for isomorphisms and traversals, and not making any classes. -- It uses 'underscoreNoPrefixNamer'. lensRules :: LensRules lensRules = LensRules { _simpleLenses = False , _generateSigs = True , _generateClasses = False , _allowIsos = True , _allowUpdates = True , _lazyPatterns = False , _classyLenses = const Nothing , _fieldToDef = underscoreNoPrefixNamer } -- | A 'FieldNamer' that strips the _ off of the field name, -- lowercases the name, and skips the field if it doesn't start with -- an '_'. underscoreNoPrefixNamer :: FieldNamer underscoreNoPrefixNamer _ _ n = case nameBase n of '_':x:xs -> [TopName (mkName (toLower x:xs))] _ -> [] -- | Construct a 'LensRules' value for generating top-level definitions -- using the given map from field names to definition names. lensRulesFor :: [(String, String)] {- ^ [(Field Name, Definition Name)] -} -> LensRules lensRulesFor fields = lensRules & lensField .~ lookingupNamer fields -- | Create a 'FieldNamer' from explicit pairings of @(fieldName, lensName)@. lookingupNamer :: [(String,String)] -> FieldNamer lookingupNamer kvs _ _ field = [ TopName (mkName v) | (k,v) <- kvs, k == nameBase field] -- | Create a 'FieldNamer' from a mapping function. If the function -- returns @[]@, it creates no lens for the field. mappingNamer :: (String -> [String]) -- ^ A function that maps a @fieldName@ to @lensName@s. -> FieldNamer mappingNamer mapper _ _ = fmap (TopName . mkName) . mapper . nameBase -- | Rules for making lenses and traversals that precompose another 'Lens'. classyRules :: LensRules classyRules = LensRules { _simpleLenses = True , _generateSigs = True , _generateClasses = True , _allowIsos = False -- generating Isos would hinder "subtyping" , _allowUpdates = True , _lazyPatterns = False , _classyLenses = \n -> case nameBase n of x:xs -> Just (mkName ("Has" ++ x:xs), mkName (toLower x:xs)) [] -> Nothing , _fieldToDef = underscoreNoPrefixNamer } -- | Rules for making lenses and traversals that precompose another 'Lens' -- using a custom function for naming the class, main class method, and a -- mapping from field names to definition names. classyRulesFor :: (String -> Maybe (String, String)) {- ^ Type Name -> Maybe (Class Name, Method Name) -} -> [(String, String)] {- ^ [(Field Name, Method Name)] -} -> LensRules classyRulesFor classFun fields = classyRules & lensClass .~ (over (mapped . both) mkName . classFun . nameBase) & lensField .~ lookingupNamer fields -- | A 'LensRules' used by 'makeClassy_'. classyRules_ :: LensRules classyRules_ = classyRules & lensField .~ \_ _ n -> [TopName (mkName ('_':nameBase n))] -- | 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\') \<$\> f b -- y _ c\@(Bar _) = pure c -- @ -- -- @ -- 'makeLenses' = 'makeLensesWith' 'lensRules' -- @ makeLenses :: Name -> DecsQ makeLenses = makeFieldOptics lensRules -- | Make lenses and traversals for a type, and create a class when the -- type has no arguments. -- -- /e.g./ -- -- @ -- data Foo = Foo { _fooX, _fooY :: 'Int' } -- 'makeClassy' ''Foo -- @ -- -- will create -- -- @ -- class HasFoo t where -- foo :: 'Lens'' t Foo -- fooX :: 'Lens'' t 'Int' -- fooX = foo . go where go f (Foo x y) = (\\x\' -> Foo x' y) \<$\> 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 -> DecsQ makeClassy = makeFieldOptics 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 -> DecsQ makeClassy_ = makeFieldOptics 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 -> DecsQ makeLensesFor fields = makeFieldOptics (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 -> DecsQ makeClassyFor clsName funName fields = makeFieldOptics $ classyRulesFor (const (Just (clsName, funName))) fields -- | Build lenses with a custom configuration. makeLensesWith :: LensRules -> Name -> DecsQ makeLensesWith = makeFieldOptics -- | 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 :: DecsQ -> DecsQ declareLenses = declareLensesWith $ lensRules & lensField .~ \_ _ n -> [TopName n] -- | Similar to 'makeLensesFor', but takes a declaration quote. declareLensesFor :: [(String, String)] -> DecsQ -> DecsQ declareLensesFor fields = declareLensesWith $ lensRulesFor fields & lensField .~ \_ _ n -> [TopName n] -- | 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 :: DecsQ -> DecsQ declareClassy = declareLensesWith $ classyRules & lensField .~ \_ _ n -> [TopName n] -- | Similar to 'makeClassyFor', but takes a declaration quote. declareClassyFor :: [(String, (String, String))] -> [(String, String)] -> DecsQ -> DecsQ declareClassyFor classes fields = declareLensesWith $ classyRulesFor (`Prelude.lookup`classes) fields & lensField .~ \_ _ n -> [TopName n] -- | Generate a 'Control.Lens.Type.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 :: DecsQ -> DecsQ declarePrisms = declareWith $ \dec -> do emit =<< liftDeclare (makeDecPrisms True dec) return dec -- | Build 'Control.Lens.Wrapped.Wrapped' instance for each newtype. declareWrapped :: DecsQ -> DecsQ declareWrapped = declareWith $ \dec -> do maybeDecs <- liftDeclare (makeWrappedForDec dec) forM_ maybeDecs emit return dec -- | @ declareFields = 'declareLensesWith' 'defaultFieldRules' @ declareFields :: DecsQ -> DecsQ declareFields = declareLensesWith 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 -> DecsQ -> DecsQ declareLensesWith rules = declareWith $ \dec -> do emit =<< lift (makeFieldOpticsForDec' rules dec) return $ stripFields dec ----------------------------------------------------------------------------- -- Internal TH Implementation ----------------------------------------------------------------------------- -- | Transform @NewtypeD@s declarations to @DataD@s and @NewtypeInstD@s to -- @DataInstD@s. deNewtype :: Dec -> Dec #if MIN_VERSION_template_haskell(2,11,0) deNewtype (NewtypeD ctx tyName args kind c d) = DataD ctx tyName args kind [c] d deNewtype (NewtypeInstD ctx tyName args kind c d) = DataInstD ctx tyName args kind [c] d #else 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 #endif deNewtype d = d -- | 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)) apps :: Type -> [Type] -> Type apps = Prelude.foldl AppT makeDataDecl :: Dec -> Maybe DataDecl makeDataDecl dec = case deNewtype dec of DataD ctx tyName args #if MIN_VERSION_template_haskell(2,11,0) _ #endif cons _ -> Just DataDecl { dataContext = ctx , tyConName = Just tyName , dataParameters = args , fullType = apps $ ConT tyName , constructors = cons } DataInstD ctx familyName args #if MIN_VERSION_template_haskell(2,11,0) _ #endif 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 } -- | 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 rewrappedTypeName `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' unwrappedTypeName [return appliedType] (return fieldType) -- Wrapped (Con a b c...) let klass = conT wrappedTypeName `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 body = appsE [varE isoValName, unwrapFun, wrapFun] let isoMethod = funD _wrapped'ValName [clause [] (normalB body) []] -- 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 overHead :: (a -> a) -> [a] -> [a] overHead _ [] = [] overHead f (x:xs) = f x : xs -- | Field rules for fields in the form @ _prefix_fieldname @ underscoreFields :: LensRules underscoreFields = defaultFieldRules & lensField .~ underscoreNamer -- | A 'FieldNamer' for 'underscoreFields'. underscoreNamer :: FieldNamer underscoreNamer _ _ field = maybeToList $ do _ <- prefix field' method <- niceLens cls <- classNaming return (MethodName (mkName cls) (mkName method)) where field' = nameBase field prefix ('_':xs) | '_' `List.elem` xs = Just (takeWhile (/= '_') xs) prefix _ = Nothing niceLens = prefix field' <&> \n -> drop (length n + 2) field' classNaming = niceLens <&> ("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. -- -- __Note__: The @prefix@ must be the same as the typename (with the first -- letter lowercased). This is a change from lens versions before lens 4.5. -- If you want the old behaviour, use 'makeLensesWith' 'abbreviatedFields' camelCaseFields :: LensRules camelCaseFields = defaultFieldRules -- | A 'FieldNamer' for 'camelCaseFields'. camelCaseNamer :: FieldNamer camelCaseNamer tyName fields field = maybeToList $ do fieldPart <- stripPrefix expectedPrefix (nameBase field) method <- computeMethod fieldPart let cls = "Has" ++ fieldPart return (MethodName (mkName cls) (mkName method)) where expectedPrefix = optUnderscore ++ overHead toLower (nameBase tyName) optUnderscore = ['_' | any (isPrefixOf "_" . nameBase) fields ] computeMethod (x:xs) | isUpper x = Just (toLower x : xs) computeMethod _ = Nothing -- | Field rules for fields in the form @ _fieldname @ (the leading -- underscore is mandatory). -- -- __Note__: The primary difference to 'camelCaseFields' is that for -- @classUnderscoreNoPrefixFields@ the field names are not expected to -- be prefixed with the type name. This might be the desired behaviour -- when the @DuplicateRecordFields@ extension is enabled. classUnderscoreNoPrefixFields :: LensRules classUnderscoreNoPrefixFields = defaultFieldRules & lensField .~ classUnderscoreNoPrefixNamer -- | A 'FieldNamer' for 'classUnderscoreNoPrefixFields'. classUnderscoreNoPrefixNamer :: FieldNamer classUnderscoreNoPrefixNamer _ _ field = maybeToList $ do fieldUnprefixed <- stripPrefix "_" (nameBase field) let className = "Has" ++ overHead toUpper fieldUnprefixed methodName = fieldUnprefixed return (MethodName (mkName className) (mkName methodName)) -- | Field rules 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. -- -- Note that @prefix@ may be any string of characters that are not uppercase -- letters. (In particular, it may be arbitrary string of lowercase letters -- and numbers) This is the behavior that 'defaultFieldRules' had in lens -- 4.4 and earlier. abbreviatedFields :: LensRules abbreviatedFields = defaultFieldRules { _fieldToDef = abbreviatedNamer } -- | A 'FieldNamer' for 'abbreviatedFields'. abbreviatedNamer :: FieldNamer abbreviatedNamer _ fields field = maybeToList $ do fieldPart <- stripMaxLc (nameBase field) method <- computeMethod fieldPart let cls = "Has" ++ fieldPart return (MethodName (mkName cls) (mkName method)) where stripMaxLc f = do x <- stripPrefix optUnderscore f case break isUpper x of (p,s) | List.null p || List.null s -> Nothing | otherwise -> Just s optUnderscore = ['_' | any (isPrefixOf "_" . nameBase) fields ] computeMethod (x:xs) | isUpper x = Just (toLower x : xs) computeMethod _ = Nothing -- | 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 -- @ -- -- For details, see 'camelCaseFields'. -- -- @ -- makeFields = 'makeLensesWith' 'defaultFieldRules' -- @ makeFields :: Name -> DecsQ makeFields = makeFieldOptics camelCaseFields -- | Generate overloaded field accessors based on field names which -- are only prefixed with an underscore (e.g. '_name'), not -- additionally with the type name (e.g. '_fooName'). -- -- This might be the desired behaviour in case the -- @DuplicateRecordFields@ language extension is used in order to get -- rid of the necessity to prefix each field name with the type name. -- -- As an example: -- -- @ -- data Foo a = Foo { _x :: 'Int', _y :: a } -- newtype Bar = Bar { _x :: 'Char' } -- makeFieldsNoPrefix ''Foo -- makeFieldsNoPrefix ''Bar -- @ -- -- will create classes -- -- @ -- class HasX s a | s -> a where -- x :: Lens' s a -- class HasY s a | s -> a where -- y :: Lens' s a -- @ -- -- together with instances -- -- @ -- instance HasX (Foo a) Int -- instance HasY (Foo a) a where -- instance HasX Bar Char where -- @ -- -- For details, see 'classUnderscoreNoPrefixFields'. -- -- @ -- makeFieldsNoPrefix = 'makeLensesWith' 'classUnderscoreNoPrefixFields' -- @ makeFieldsNoPrefix :: Name -> DecsQ makeFieldsNoPrefix = makeFieldOptics classUnderscoreNoPrefixFields defaultFieldRules :: LensRules defaultFieldRules = LensRules { _simpleLenses = True , _generateSigs = True , _generateClasses = True -- classes will still be skipped if they already exist , _allowIsos = False -- generating Isos would hinder field class reuse , _allowUpdates = True , _lazyPatterns = False , _classyLenses = const Nothing , _fieldToDef = camelCaseNamer } -- Declaration quote stuff declareWith :: (Dec -> Declare Dec) -> DecsQ -> DecsQ declareWith fun = (runDeclare . traverseDataAndNewtype fun =<<) -- | Monad for emitting top-level declarations as a side effect. We also track -- the set of field class 'Name's that have been created and consult them to -- avoid creating duplicate classes. -- See #463 for more information. type Declare = WriterT (Endo [Dec]) (StateT (Set Name) Q) liftDeclare :: Q a -> Declare a liftDeclare = lift . lift runDeclare :: Declare [Dec] -> DecsQ runDeclare dec = do (out, endo) <- evalStateT (runWriterT dec) Set.empty 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. #if MIN_VERSION_template_haskell(2,11,0) InstanceD moverlap ctx inst body -> InstanceD moverlap ctx inst <$> traverse go body #else InstanceD ctx inst body -> InstanceD ctx inst <$> traverse go body #endif _ -> pure dec stripFields :: Dec -> Dec stripFields dec = case dec of #if MIN_VERSION_template_haskell(2,11,0) DataD ctx tyName tyArgs kind cons derivings -> DataD ctx tyName tyArgs kind (map deRecord cons) derivings NewtypeD ctx tyName tyArgs kind con derivings -> NewtypeD ctx tyName tyArgs kind (deRecord con) derivings DataInstD ctx tyName tyArgs kind cons derivings -> DataInstD ctx tyName tyArgs kind (map deRecord cons) derivings NewtypeInstD ctx tyName tyArgs kind con derivings -> NewtypeInstD ctx tyName tyArgs kind (deRecord con) derivings #else 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 #endif _ -> 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) #if MIN_VERSION_template_haskell(2,11,0) deRecord con@GadtC{} = con deRecord (RecGadtC ns fields retTy) = GadtC ns (map dropFieldName fields) retTy #endif #if MIN_VERSION_template_haskell(2,11,0) dropFieldName :: VarBangType -> BangType #else dropFieldName :: VarStrictType -> StrictType #endif dropFieldName (_, str, typ) = (str, typ)