lens-3.10.0.1: src/Control/Lens/TH.hs
{-# 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 <ekmett@gmail.com>
-- 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
#ifdef HLINT
{-# 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
-- | 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