{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE OverloadedLists #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TypeFamilies #-}
module Dhall.Nix (
dhallToNix
, CompileError(..)
) where
import Control.Exception (Exception)
import Data.Foldable (toList)
import Data.Fix (Fix(..))
import Data.Traversable (for)
import Data.Typeable (Typeable)
import Data.Void (absurd)
import Dhall.Core (Chunks(..), Const(..), Expr(..), MultiLet(..), Var(..))
import Dhall.TypeCheck (X)
import Nix.Atoms (NAtom(..))
import Nix.Expr
( Antiquoted(..)
, Binding(..)
, NBinaryOp(..)
, NExprF(..)
, NKeyName(..)
, NString(..)
, Params(..)
, (@@)
, (==>)
, ($+)
)
import qualified Data.Text
import qualified Dhall.Core
import qualified Dhall.Map
import qualified NeatInterpolation
import qualified Nix
data CompileError
= CannotReferenceShadowedVariable Var
| CannotProjectByType
deriving (Typeable)
instance Show CompileError where
show (CannotReferenceShadowedVariable v) =
Data.Text.unpack [NeatInterpolation.text|
$_ERROR: Cannot reference shadowed variable
Explanation: Whenever you introduce two variables of the same name, the latter
variable takes precedence:
This ❰x❱ ...
⇩
┌───────────────────────────────┐
│ λ(x : Text) → λ(x : Text) → x │
└───────────────────────────────┘
⇧
... refers to this ❰x❱
The former variable is "shadowed":
┌───────────────────────────────┐
│ λ(x : Text) → λ(x : Text) → x │
└───────────────────────────────┘
⇧
This ❰x❱ is shadowed
... and Dhall lets you reference shadowed variables using the ❰@❱ notation:
This ❰x❱ ...
⇩
┌─────────────────────────────────┐
│ λ(x : Text) → λ(x : Text) → x@1 │
└─────────────────────────────────┘
⇧
... now refers to this ❰x❱
However, the Nix language does not let you reference shadowed variables and
there is nothing analogous to ❰@❱ in Nix
Your code contains the following expression:
↳ $txt
... which references a shadowed variable and therefore cannot be translated to
Nix
|]
where
txt = Dhall.Core.pretty v
show CannotProjectByType =
Data.Text.unpack [NeatInterpolation.text|
$_ERROR: Cannot project by type
The ❰dhall-to-nix❱ compiler does not support projecting out a subset of a record
by the expected type (i.e. ❰someRecord.(someType)❱
|]
_ERROR :: Data.Text.Text
_ERROR = "\ESC[1;31mError\ESC[0m"
instance Exception CompileError
dhallToNix :: Expr s X -> Either CompileError (Fix NExprF)
dhallToNix e = loop (Dhall.Core.normalize e)
where
loop (Const _) = return (Fix (NSet []))
loop (Var (V a 0)) = return (Fix (NSym a))
loop (Var a ) = Left (CannotReferenceShadowedVariable a)
loop (Lam a _ c) = do
c' <- loop c
return (Fix (NAbs (Param a) c'))
loop (Pi _ _ _) = return (Fix (NSet []))
loop (App None _) = do
return (Fix (NConstant NNull))
loop (App (Field (Union kts) k) v) = do
v' <- loop v
let e0 = do
k' <- Dhall.Map.keys kts
return (k', Nothing)
let e2 = Fix (NBinary NApp (Fix (NSym k)) v')
return (Fix (NAbs (ParamSet e0 False Nothing) e2))
loop (App a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NApp a' b'))
loop (Let a0 b0) = do
let MultiLet as b = Dhall.Core.multiLet a0 b0
as' <- for as $ \a -> do
val <- loop $ Dhall.Core.value a
pure $ NamedVar [StaticKey $ Dhall.Core.variable a] val Nix.nullPos
b' <- loop b
return (Fix (NLet (toList as') b'))
loop (Annot a _) = loop a
loop Bool = return (Fix (NSet []))
loop (BoolLit b) = return (Fix (NConstant (NBool b)))
loop (BoolAnd a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NAnd a' b'))
loop (BoolOr a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NOr a' b'))
loop (BoolEQ a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NEq a' b'))
loop (BoolNE a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NNEq a' b'))
loop (BoolIf a b c) = do
a' <- loop a
b' <- loop b
c' <- loop c
return (Fix (NIf a' b' c'))
loop Natural = return (Fix (NSet []))
loop (NaturalLit n) = return (Fix (NConstant (NInt (fromIntegral n))))
loop NaturalFold = do
let e0 = Fix (NBinary NMinus "n" (Fix (NConstant (NInt 1))))
let e1 = Fix (NBinary NApp (Fix (NBinary NApp (Fix (NBinary NApp "naturalFold" e0)) "t")) "succ")
let e2 = Fix (NBinary NApp "succ" (Fix (NBinary NApp e1 "zero")))
let e3 = Fix (NBinary NLte "n" (Fix (NConstant (NInt 0))))
let e4 = Fix (NAbs "succ" (Fix (NAbs "zero" (Fix (NIf e3 "zero" e2)))))
let e5 = Fix (NAbs "n" (Fix (NAbs "t" e4)))
return (Fix (NLet [NamedVar ["naturalFold"] e5 Nix.nullPos] "naturalFold"))
loop NaturalBuild = do
let e0 = Fix (NBinary NPlus "n" (Fix (NConstant (NInt 1))))
let e1 = Fix (NBinary NApp (Fix (NBinary NApp "k" (Fix (NSet [])))) (Fix (NAbs "n" e0)))
return (Fix (NAbs "k" (Fix (NBinary NApp e1 (Fix (NConstant (NInt 0)))))))
loop NaturalIsZero = do
let e0 = Fix (NBinary NEq "n" (Fix (NConstant (NInt 0))))
return (Fix (NAbs "n" e0))
loop NaturalEven = do
let e0 = Fix (NBinary NMinus "n" (Fix (NConstant (NInt 2))))
let e1 = Fix (NBinary NApp "naturalEven" e0)
let e2 = Fix (NBinary NNEq "n" (Fix (NConstant (NInt 1))))
let e3 = Fix (NBinary NEq "n" (Fix (NConstant (NInt 0))))
let e4 = Fix (NBinary NOr e3 (Fix (NBinary NAnd e2 e1)))
let e5 = NamedVar ["naturalEven"] (Fix (NAbs "n" e4)) Nix.nullPos
let e6 = Fix (NBinary NMinus (Fix (NConstant (NInt 0))) "n")
let e7 = Fix (NBinary NLte "n" (Fix (NConstant (NInt 0))))
let e8 = Fix (NAbs "n" (Fix (NBinary NApp "naturalEven" (Fix (NIf e7 e6 "n")))))
return (Fix (NLet [e5] e8))
loop NaturalOdd = do
let e0 = Fix (NBinary NMinus "n" (Fix (NConstant (NInt 2))))
let e1 = Fix (NBinary NApp "naturalOdd" e0)
let e2 = Fix (NBinary NNEq "n" (Fix (NConstant (NInt 0))))
let e3 = Fix (NBinary NEq "n" (Fix (NConstant (NInt 1))))
let e4 = Fix (NBinary NOr e3 (Fix (NBinary NAnd e2 e1)))
let e5 = NamedVar ["naturalOdd"] (Fix (NAbs "n" e4)) Nix.nullPos
let e6 = Fix (NBinary NMinus (Fix (NConstant (NInt 0))) "n")
let e7 = Fix (NBinary NLte "n" (Fix (NConstant (NInt 0))))
let e8 = Fix (NAbs "n" (Fix (NBinary NApp "naturalOdd" (Fix (NIf e7 e6 "n")))))
return (Fix (NLet [e5] e8))
loop NaturalShow = do
return "toString"
loop NaturalSubtract = do
let e0 = NamedVar ["z"] (Fix (NBinary NMinus "y" "x")) Nix.nullPos
let e1 = Fix (NBinary NLt "z" (Fix (NConstant (NInt 0))))
let e2 = Fix (NConstant (NInt 0))
let e3 = "z"
let e4 = Fix (NIf e1 e2 e3)
let e5 = Fix (NLet [e0] e4)
return (Fix (NAbs "x" (Fix (NAbs "y" e5))))
loop NaturalToInteger = do
return (Fix (NAbs "n" "n"))
loop (NaturalPlus a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NPlus a' b'))
loop (NaturalTimes a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NMult a' b'))
loop Integer = return (Fix (NSet []))
loop (IntegerLit n) = return (Fix (NConstant (NInt (fromIntegral n))))
loop IntegerShow = do
let e0 = Fix (NBinary NApp "toString" "x")
let e1 = Fix (NBinary NPlus (Fix (NStr "+")) e0)
let e2 = Fix (NBinary NLte (Fix (NConstant (NInt 0))) "x")
let e3 = Fix (NAbs "x" (Fix (NIf e2 e1 e0)))
return e3
loop IntegerToDouble = do
return (Fix (NAbs "x" "x"))
loop Double = return (Fix (NSet []))
loop (DoubleLit n) = return (Fix (NConstant (NFloat (realToFrac n))))
loop DoubleShow = do
return "toString"
loop Text = return (Fix (NSet []))
loop (TextLit (Chunks abs_ c)) = do
let process (a, b) = do
b' <- loop b
return [Plain a, Antiquoted b']
abs' <- mapM process abs_
let chunks = concat abs' ++ [Plain c]
return (Fix (NStr (DoubleQuoted chunks)))
loop (TextAppend a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NPlus a' b'))
loop TextShow = do
let from =
Nix.mkList
[ Nix.mkStr "\""
, Nix.mkStr "$"
, Nix.mkStr "\\"
, Nix.mkStr "\n"
, Nix.mkStr "\r"
, Nix.mkStr "\t"
]
let to =
Nix.mkList
[ Nix.mkStr "\\\""
, Nix.mkStr "\\u0024"
, Nix.mkStr "\\\\"
, Nix.mkStr "\\n"
, Nix.mkStr "\\r"
, Nix.mkStr "\\t"
]
let replaced = "builtins.replaceStrings" @@ from @@ to @@ "t"
let quoted = Nix.mkStr "\"" $+ replaced $+ Nix.mkStr "\""
return ("t" ==> quoted)
loop List = return (Fix (NAbs "t" (Fix (NSet []))))
loop (ListAppend a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NConcat a' b'))
loop (ListLit _ bs) = do
bs' <- mapM loop (toList bs)
return (Fix (NList bs'))
loop ListBuild = do
let e0 = Fix (NBinary NApp "k" (Fix (NSet [])))
let e1 = Fix (NBinary NConcat (Fix (NList ["x"])) "xs")
let e2 = Fix (NBinary NApp e0 (Fix (NAbs "x" (Fix (NAbs "xs" e1)))))
let e3 = Fix (NAbs "k" (Fix (NBinary NApp e2 (Fix (NList [])))))
return (Fix (NAbs "t" e3))
loop ListFold = do
let e0 = Fix (NBinary NApp "f" (Fix (NBinary NApp (Fix (NBinary NApp "cons" "y")) "ys")))
let e1 = Fix (NAbs "f" (Fix (NAbs "y" (Fix (NAbs "ys" e0)))))
let e2 = Fix (NBinary NApp "builtins.foldl'" e1)
let e3 = Fix (NBinary NApp (Fix (NBinary NApp e2 (Fix (NAbs "ys" "ys")))) "xs")
let e4 = Fix (NAbs "xs" (Fix (NAbs "t" (Fix (NAbs "cons" e3)))))
return (Fix (NAbs "t" e4))
loop ListLength = return (Fix (NAbs "t" "builtins.length"))
loop ListHead = do
let e0 = Fix (NBinary NApp "builtins.head" "xs")
let e1 = Fix (NBinary NEq "xs" (Fix (NList [])))
let e2 = Fix (NAbs "xs" (Fix (NIf e1 (Fix (NConstant NNull)) e0)))
return (Fix (NAbs "t" e2))
loop ListLast = do
let e0 = Fix (NBinary NApp "builtins.length" "xs")
let e1 = Fix (NBinary NMinus e0 (Fix (NConstant (NInt 1))))
let e2 = Fix (NBinary NApp (Fix (NBinary NApp "builtins.elemAt" "xs")) e1)
let e3 = Fix (NBinary NEq "xs" (Fix (NList [])))
let e4 = Fix (NAbs "xs" (Fix (NIf e3 (Fix (NConstant NNull)) e2)))
return (Fix (NAbs "t" e4))
loop ListIndexed = do
let e0 = Fix (NBinary NApp "builtins.length" "xs")
let e1 = Fix (NBinary NApp (Fix (NBinary NApp "builtins.elemAt" "xs")) "i")
let e2 =
[ NamedVar ["index"] "i" Nix.nullPos
, NamedVar ["value"] e1 Nix.nullPos
]
let e3 = Fix (NBinary NApp "builtins.genList" (Fix (NAbs "i" (Fix (NSet e2)))))
return (Fix (NAbs "t" (Fix (NAbs "xs" (Fix (NBinary NApp e3 e0))))))
loop ListReverse = do
let e0 = Fix (NBinary NMinus "n" "i")
let e1 = Fix (NBinary NMinus e0 (Fix (NConstant (NInt 1))))
let e2 = Fix (NBinary NApp (Fix (NBinary NApp "builtins.elemAt" "xs")) e1)
let e3 = Fix (NBinary NApp "builtins.genList" (Fix (NAbs "i" e2)))
let e4 = Fix (NBinary NApp e3 "n")
let e5 = Fix (NBinary NApp "builtins.length" "xs")
let e6 = Fix (NAbs "xs" (Fix (NLet [NamedVar ["n"] e5 Nix.nullPos] e4)))
return (Fix (NAbs "t" e6))
loop Optional = return (Fix (NAbs "t" (Fix (NSet []))))
loop (Some a) = loop a
loop None = return (Fix (NConstant NNull))
loop OptionalFold = do
let e0 = Fix (NBinary NEq "x" (Fix (NConstant NNull)))
let e1 = Fix (NIf e0 "nothing" (Fix (NBinary NApp "just" "x")))
let e2 = Fix (NAbs "t" (Fix (NAbs "just" (Fix (NAbs "nothing" e1)))))
return (Fix (NAbs "t" (Fix (NAbs "x" e2))))
loop OptionalBuild = do
let e0 = Pi "nothing" "optional" "optional"
let e1 = Pi "just" (Pi "_" "a" "optional") e0
let e2 = Pi "optional" (Const Type) e1
let e3 = App None "a"
let e4 = Lam "x" "a" (Some "x")
let e5 = App (App (App "f" (App Optional "a")) e4) e3
loop (Lam "a" (Const Type) (Lam "f" e2 e5))
loop (Record _) = return (Fix (NSet []))
loop (RecordLit a) = do
a' <- traverse loop a
let a'' = do
(k, v) <- Dhall.Map.toList a'
return (NamedVar [StaticKey k] v Nix.nullPos)
return (Fix (NSet a''))
loop (Union _) = return (Fix (NSet []))
loop (Combine a b) = do
a' <- loop a
b' <- loop b
let e0 = Fix (NBinary NApp (Fix (NBinary NApp "map" "toKeyVals")) "ks")
let e1 = Fix (NBinary NApp "builtins.concatLists" e0)
let e2 = Fix (NBinary NApp "builtins.listToAttrs" e1)
let defL = Fix (NBinary NApp (Fix (NBinary NApp "builtins.hasAttr" "k")) "kvsL")
let defR = Fix (NBinary NApp (Fix (NBinary NApp "builtins.hasAttr" "k")) "kvsR")
let valL = Fix (NBinary NApp (Fix (NBinary NApp "builtins.getAttr" "k")) "kvsL")
let valR = Fix (NBinary NApp (Fix (NBinary NApp "builtins.getAttr" "k")) "kvsR")
let empty_ = Fix (NList [])
let toNameValue v =
let bindings =
[ NamedVar ["name" ] "k" Nix.nullPos
, NamedVar ["value"] v Nix.nullPos
]
in Fix (NList [Fix (NSet bindings)])
let e3 = Fix (NBinary NApp (Fix (NBinary NApp "combine" valL)) valR)
let e4 = Fix (NBinary NApp "builtins.isAttrs" valL)
let e5 = Fix (NBinary NApp "builtins.isAttrs" valR)
let e6 = Fix (NBinary NAnd e4 e5)
let e7 = Fix (NIf e6 (toNameValue e3) (toNameValue valR))
let e8 = Fix (NIf defR e7 (toNameValue valL))
let e9 = Fix (NIf defR (toNameValue valR) empty_)
let toKeyVals = Fix (NAbs "k" (Fix (NIf defL e8 e9)))
let ksL = Fix (NBinary NApp "builtins.attrNames" "kvsL")
let ksR = Fix (NBinary NApp "builtins.attrNames" "kvsR")
let ks = Fix (NBinary NConcat ksL ksR)
let e10 =
[ NamedVar ["ks" ] ks Nix.nullPos
, NamedVar ["toKeyVals"] toKeyVals Nix.nullPos
]
let combine = Fix (NAbs "kvsL" (Fix (NAbs "kvsR" (Fix (NLet e10 e2)))))
let e11 = Fix (NBinary NApp (Fix (NBinary NApp "combine" a')) b')
return (Fix (NLet [NamedVar ["combine"] combine Nix.nullPos] e11))
loop (CombineTypes _ _) = return (Fix (NSet []))
loop (Merge a b _) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NApp b' a'))
loop (ToMap a _) = do
a' <- loop a
let ks = Fix (NBinary NApp "builtins.attrNames" "kvs")
let v = Fix (NBinary NApp (Fix (NBinary NApp "builtins.getAttr" "k")) "kvs")
let setBindings =
[ NamedVar [StaticKey "mapKey"] "k" Nix.nullPos
, NamedVar [StaticKey "mapValue"] v Nix.nullPos
]
let map_ = Fix (NBinary NApp "map" (Fix (NAbs "k" (Fix (NSet setBindings)))))
let toMap = Fix (NAbs "kvs" (Fix (NBinary NApp map_ ks)))
return (Fix (NBinary NApp toMap a'))
loop (Prefer a b) = do
a' <- loop a
b' <- loop b
return (Fix (NBinary NUpdate a' b'))
loop (Field (Union kts) k) =
case Dhall.Map.lookup k kts of
Just ( Just _ ) -> do
let e0 = do
k' <- Dhall.Map.keys kts
return (k', Nothing)
let e2 = Fix (NBinary NApp (Fix (NSym k)) (Fix (NSym "x")))
return (Fix (NAbs (Param "x") (Fix (NAbs (ParamSet e0 False Nothing) e2))))
_ -> do
let e0 = do
k' <- Dhall.Map.keys kts
return (k', Nothing)
let e2 = Fix (NSym k)
return (Fix (NAbs (ParamSet e0 False Nothing) e2))
loop (Field a b) = do
a' <- loop a
return (Fix (NSelect a' [StaticKey b] Nothing))
loop (Project a (Left b)) = do
a' <- loop a
let b' = fmap StaticKey (toList b)
return (Fix (NSet [Inherit (Just a') b' Nix.nullPos]))
loop (Project _ (Right _)) = do
Left CannotProjectByType
loop (Assert _) = do
return (Fix (NSet []))
loop (Equivalent _ _) = do
return (Fix (NSet []))
loop (ImportAlt a _) = loop a
loop (Note _ b) = loop b
loop (Embed x) = absurd x