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Parser.hs
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Parser.hs
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{-# LANGUAGE CPP #-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedStrings #-}
{-# OPTIONS_GHC -fno-warn-name-shadowing #-}
{-# OPTIONS_GHC -Wno-missing-signatures #-}
module Nix.Parser
( parseNixFile
, parseNixFileLoc
, parseNixText
, parseNixTextLoc
, parseFromFileEx
, parseFromText
, Result(..)
, reservedNames
, OperatorInfo(..)
, NSpecialOp(..)
, NAssoc(..)
, NOperatorDef
, getUnaryOperator
, getBinaryOperator
, getSpecialOperator
) where
import Control.Applicative hiding (many, some)
import Control.DeepSeq
import Control.Monad
import Control.Monad.IO.Class
import Data.Char (isAlpha, isDigit, isSpace)
import Data.Data (Data(..))
import Data.Foldable (concat)
import Data.Functor
import Data.Functor.Identity
import Data.HashSet (HashSet)
import qualified Data.HashSet as HashSet
import Data.List.NonEmpty (NonEmpty(..))
import qualified Data.List.NonEmpty as NE
import qualified Data.Map as Map
import Data.Text (Text)
import Data.Text hiding (map, foldr1, concat, concatMap, zipWith)
import qualified Data.Text.IO as T
import Data.Typeable (Typeable)
import Data.Void
import GHC.Generics hiding (Prefix)
import Nix.Expr hiding (($>))
import Nix.Strings
import Text.Megaparsec
import Text.Megaparsec.Char
import qualified Text.Megaparsec.Char.Lexer as L
import Text.Megaparsec.Expr
import Text.PrettyPrint.ANSI.Leijen (Doc, text)
infixl 3 <+>
(<+>) :: MonadPlus m => m a -> m a -> m a
(<+>) = mplus
--------------------------------------------------------------------------------
nixExprLoc :: Parser NExprLoc
nixExprLoc = makeExprParser nixTerm $ map (map snd) (nixOperators nixSelector)
antiStart :: Parser Text
antiStart = symbol "${" <?> show ("${" :: String)
nixAntiquoted :: Parser a -> Parser (Antiquoted a NExprLoc)
nixAntiquoted p =
Antiquoted <$> (antiStart *> nixToplevelForm <* symbol "}")
<+> Plain <$> p
<?> "anti-quotation"
selDot :: Parser ()
selDot = try (symbol "." *> notFollowedBy nixPath) <?> "."
nixSelect :: Parser NExprLoc -> Parser NExprLoc
nixSelect term = do
res <- build
<$> term
<*> optional ((,) <$> (selDot *> nixSelector)
<*> optional (reserved "or" *> nixTerm))
continues <- optional $ lookAhead selDot
case continues of
Nothing -> pure res
Just _ -> nixSelect (pure res)
where
build :: NExprLoc
-> Maybe (Ann SrcSpan (NAttrPath NExprLoc), Maybe NExprLoc)
-> NExprLoc
build t Nothing = t
build t (Just (s,o)) = nSelectLoc t s o
nixSelector :: Parser (Ann SrcSpan (NAttrPath NExprLoc))
nixSelector = annotateLocation $ do
(x:xs) <- keyName `sepBy1` selDot
return $ x :| xs
nixTerm :: Parser NExprLoc
nixTerm = do
c <- try $ lookAhead $ satisfy $ \x ->
pathChar x ||
x == '(' ||
x == '{' ||
x == '[' ||
x == '<' ||
x == '/' ||
x == '"' ||
x == '\''
case c of
'(' -> nixSelect nixParens
'{' -> nixSelect nixSet
'[' -> nixList
'<' -> nixSPath
'/' -> nixPath
'"' -> nixStringExpr
'\'' -> nixStringExpr
_ -> msum $
[ nixSelect nixSet | c == 'r' ] ++
[ nixPath | pathChar c ] ++
if isDigit c
then [ nixFloat
, nixInt ]
else [ nixUri | isAlpha c ] ++
[ nixBool | c == 't' || c == 'f' ] ++
[ nixNull | c == 'n' ] ++
[ nixSelect nixSym ]
nixToplevelForm :: Parser NExprLoc
nixToplevelForm = keywords <+> nixLambda <+> nixExprLoc
where
keywords = nixLet <+> nixIf <+> nixAssert <+> nixWith
nixSym :: Parser NExprLoc
nixSym = annotateLocation1 $ mkSymF <$> identifier
nixInt :: Parser NExprLoc
nixInt = annotateLocation1 (mkIntF <$> integer <?> "integer")
nixFloat :: Parser NExprLoc
nixFloat = annotateLocation1 (try (mkFloatF . realToFrac <$> float) <?> "float")
nixBool :: Parser NExprLoc
nixBool = annotateLocation1 (bool "true" True <+>
bool "false" False) <?> "bool" where
bool str b = mkBoolF b <$ reserved str
nixNull :: Parser NExprLoc
nixNull = annotateLocation1 (mkNullF <$ reserved "null" <?> "null")
nixParens :: Parser NExprLoc
nixParens = parens nixToplevelForm <?> "parens"
nixList :: Parser NExprLoc
nixList = annotateLocation1 (brackets (NList <$> many nixTerm) <?> "list")
pathChar :: Char -> Bool
pathChar x = isAlpha x || isDigit x || x == '.' || x == '_' || x == '-' || x == '+' || x == '~'
slash :: Parser Char
slash = try (char '/' <* notFollowedBy (satisfy (\x -> x == '/' || x == '*' || isSpace x)))
<?> "slash"
-- | A path surrounded by angle brackets, indicating that it should be
-- looked up in the NIX_PATH environment variable at evaluation.
nixSPath :: Parser NExprLoc
nixSPath = annotateLocation1
(mkPathF True <$> try (char '<' *> many (satisfy pathChar <+> slash) <* symbol ">")
<?> "spath")
pathStr :: Parser FilePath
pathStr = lexeme $ liftM2 (++) (many (satisfy pathChar))
(Prelude.concat <$> some (liftM2 (:) slash (some (satisfy pathChar))))
nixPath :: Parser NExprLoc
nixPath = annotateLocation1 (try (mkPathF False <$> pathStr) <?> "path")
nixLet :: Parser NExprLoc
nixLet = annotateLocation1 (reserved "let"
*> (letBody <+> letBinders)
<?> "let block")
where
letBinders = NLet
<$> nixBinders
<*> (reserved "in" *> nixToplevelForm)
-- Let expressions `let {..., body = ...}' are just desugared
-- into `(rec {..., body = ...}).body'.
letBody = (\x -> NSelect x (StaticKey "body" :| []) Nothing) <$> aset
aset = annotateLocation1 $ NRecSet <$> braces nixBinders
nixIf :: Parser NExprLoc
nixIf = annotateLocation1 (NIf
<$> (reserved "if" *> nixExprLoc)
<*> (reserved "then" *> nixToplevelForm)
<*> (reserved "else" *> nixToplevelForm)
<?> "if")
nixAssert :: Parser NExprLoc
nixAssert = annotateLocation1 (NAssert
<$> (reserved "assert" *> nixExprLoc)
<*> (semi *> nixToplevelForm)
<?> "assert")
nixWith :: Parser NExprLoc
nixWith = annotateLocation1 (NWith
<$> (reserved "with" *> nixToplevelForm)
<*> (semi *> nixToplevelForm)
<?> "with")
nixLambda :: Parser NExprLoc
nixLambda = nAbs <$> annotateLocation (try argExpr) <*> nixToplevelForm
nixStringExpr :: Parser NExprLoc
nixStringExpr = nStr <$> annotateLocation nixString
nixUri :: Parser NExprLoc
nixUri = annotateLocation1 $ lexeme $ try $ do
start <- letterChar
protocol <- many $ satisfy $ \x ->
isAlpha x || isDigit x || x `elem` ("+-." :: String)
_ <- string ":"
address <- some $ satisfy $ \x ->
isAlpha x || isDigit x || x `elem` ("%/?:@&=+$,-_.!~*'" :: String)
return $ NStr $
DoubleQuoted [Plain $ pack $ start : protocol ++ ':' : address]
nixString :: Parser (NString NExprLoc)
nixString = lexeme (doubleQuoted <+> indented <?> "string")
where
doubleQuoted :: Parser (NString NExprLoc)
doubleQuoted = DoubleQuoted . removePlainEmpty . mergePlain
<$> (doubleQ *> many (stringChar doubleQ (void $ char '\\')
doubleEscape)
<* doubleQ)
<?> "double quoted string"
doubleQ = void (char '"')
doubleEscape = Plain . singleton <$> (char '\\' *> escapeCode)
indented :: Parser (NString NExprLoc)
indented = stripIndent
<$> (indentedQ *> many (stringChar indentedQ indentedQ
indentedEscape)
<* indentedQ)
<?> "indented string"
indentedQ = void (string "''" <?> "\"''\"")
indentedEscape = try $ do
indentedQ
(Plain <$> ("''" <$ char '\'' <+> "$" <$ char '$')) <+> do
_ <- char '\\'
c <- escapeCode
pure $ if c == '\n'
then EscapedNewline
else Plain $ singleton c
stringChar end escStart esc =
Antiquoted <$> (antiStart *> nixToplevelForm <* char '}')
<+> Plain . singleton <$> char '$'
<+> esc
<+> Plain . pack <$> some plainChar
where
plainChar =
notFollowedBy (end <+> void (char '$') <+> escStart) *> anyChar
escapeCode = msum [ c <$ char e | (c,e) <- escapeCodes ] <+> anyChar
-- | Gets all of the arguments for a function.
argExpr :: Parser (Params NExprLoc)
argExpr = msum [atLeft, onlyname, atRight] <* symbol ":" where
-- An argument not in curly braces. There's some potential ambiguity
-- in the case of, for example `x:y`. Is it a lambda function `x: y`, or
-- a URI `x:y`? Nix syntax says it's the latter. So we need to fail if
-- there's a valid URI parse here.
onlyname = msum [nixUri >> unexpected (Label ('v' NE.:| "alid uri")),
Param <$> identifier]
-- Parameters named by an identifier on the left (`args @ {x, y}`)
atLeft = try $ do
name <- identifier <* symbol "@"
(variadic, params) <- params
return $ ParamSet params variadic (Just name)
-- Parameters named by an identifier on the right, or none (`{x, y} @ args`)
atRight = do
(variadic, params) <- params
name <- optional $ symbol "@" *> identifier
return $ ParamSet params variadic name
-- Return the parameters set.
params = do
(args, dotdots) <- braces getParams
return (dotdots, args)
-- Collects the parameters within curly braces. Returns the parameters and
-- a boolean indicating if the parameters are variadic.
getParams :: Parser ([(Text, Maybe NExprLoc)], Bool)
getParams = go [] where
-- Attempt to parse `...`. If this succeeds, stop and return True.
-- Otherwise, attempt to parse an argument, optionally with a
-- default. If this fails, then return what has been accumulated
-- so far.
go acc = ((acc, True) <$ symbol "...") <+> getMore acc
getMore acc =
-- Could be nothing, in which just return what we have so far.
option (acc, False) $ do
-- Get an argument name and an optional default.
pair <- liftM2 (,) identifier (optional $ question *> nixToplevelForm)
-- Either return this, or attempt to get a comma and restart.
option (acc ++ [pair], False) $ comma >> go (acc ++ [pair])
nixBinders :: Parser [Binding NExprLoc]
nixBinders = (inherit <+> namedVar) `endBy` semi where
inherit = do
-- We can't use 'reserved' here because it would consume the whitespace
-- after the keyword, which is not exactly the semantics of C++ Nix.
try $ string "inherit" *> lookAhead (void (satisfy reservedEnd))
p <- getPosition
x <- whiteSpace *> optional scope
Inherit x <$> many keyName <*> pure p <?> "inherited binding"
namedVar = do
p <- getPosition
NamedVar <$> (annotated <$> nixSelector)
<*> (equals *> nixToplevelForm)
<*> pure p
<?> "variable binding"
scope = parens nixToplevelForm <?> "inherit scope"
keyName :: Parser (NKeyName NExprLoc)
keyName = dynamicKey <+> staticKey where
staticKey = StaticKey <$> identifier
dynamicKey = DynamicKey <$> nixAntiquoted nixString
nixSet :: Parser NExprLoc
nixSet = annotateLocation1 ((isRec <*> braces nixBinders) <?> "set") where
isRec = (reserved "rec" $> NRecSet <?> "recursive set")
<+> pure NSet
parseNixFile :: MonadIO m => FilePath -> m (Result NExpr)
parseNixFile =
parseFromFileEx $ stripAnnotation <$> (whiteSpace *> nixToplevelForm <* eof)
parseNixFileLoc :: MonadIO m => FilePath -> m (Result NExprLoc)
parseNixFileLoc = parseFromFileEx (whiteSpace *> nixToplevelForm <* eof)
parseNixText :: Text -> Result NExpr
parseNixText =
parseFromText $ stripAnnotation <$> (whiteSpace *> nixToplevelForm <* eof)
parseNixTextLoc :: Text -> Result NExprLoc
parseNixTextLoc = parseFromText (whiteSpace *> nixToplevelForm <* eof)
{- Parser.Library -}
skipLineComment' :: Tokens Text -> Parser ()
skipLineComment' prefix =
string prefix
*> void (takeWhileP (Just "character") (\x -> x /= '\n' && x /= '\r'))
whiteSpace :: Parser ()
whiteSpace = L.space space1 lineCmnt blockCmnt
where
lineCmnt = skipLineComment' "#"
blockCmnt = L.skipBlockComment "/*" "*/"
lexeme :: Parser a -> Parser a
lexeme p = p <* whiteSpace
symbol :: Text -> Parser Text
symbol = lexeme . string
reservedEnd :: Char -> Bool
reservedEnd x = isSpace x ||
x == '{' || x == '(' || x == '[' ||
x == '}' || x == ')' || x == ']' ||
x == ';' || x == ':' || x == '.' ||
x == '"' || x == '\'' || x == ','
reserved :: Text -> Parser ()
reserved n = lexeme $ try $
string n *> lookAhead (void (satisfy reservedEnd) <|> eof)
identifier = lexeme $ try $ do
ident <- cons <$> satisfy (\x -> isAlpha x || x == '_')
<*> takeWhileP Nothing identLetter
guard (not (ident `HashSet.member` reservedNames))
return ident
where
identLetter x = isAlpha x || isDigit x || x == '_' || x == '\'' || x == '-'
parens = between (symbol "(") (symbol ")")
braces = between (symbol "{") (symbol "}")
-- angles = between (symbol "<") (symbol ">")
brackets = between (symbol "[") (symbol "]")
semi = symbol ";"
comma = symbol ","
-- colon = symbol ":"
-- dot = symbol "."
equals = symbol "="
question = symbol "?"
integer :: Parser Integer
integer = lexeme L.decimal
float :: Parser Double
float = lexeme L.float
reservedNames :: HashSet Text
reservedNames = HashSet.fromList
[ "let", "in"
, "if", "then", "else"
, "assert"
, "with"
, "rec"
, "inherit"
, "true", "false" ]
type Parser = ParsecT Void Text Identity
data Result a = Success a | Failure Doc deriving Show
parseFromFileEx :: MonadIO m => Parser a -> FilePath -> m (Result a)
parseFromFileEx p path = do
txt <- liftIO (T.readFile path)
return $ either (Failure . text . parseErrorPretty' txt) Success
$ parse p path txt
parseFromText :: Parser a -> Text -> Result a
parseFromText p txt =
either (Failure . text . parseErrorPretty' txt) Success $
parse p "<string>" txt
{- Parser.Operators -}
data NSpecialOp = NHasAttrOp | NSelectOp
deriving (Eq, Ord, Generic, Typeable, Data, Show, NFData)
data NAssoc = NAssocNone | NAssocLeft | NAssocRight
deriving (Eq, Ord, Generic, Typeable, Data, Show, NFData)
data NOperatorDef
= NUnaryDef Text NUnaryOp
| NBinaryDef Text NBinaryOp NAssoc
| NSpecialDef Text NSpecialOp NAssoc
deriving (Eq, Ord, Generic, Typeable, Data, Show, NFData)
annotateLocation :: Parser a -> Parser (Ann SrcSpan a)
annotateLocation p = do
begin <- getPosition
res <- p
end <- getPosition
pure $ Ann (SrcSpan begin end) res
annotateLocation1 :: Parser (NExprF NExprLoc) -> Parser NExprLoc
annotateLocation1 = fmap annToAnnF . annotateLocation
manyUnaryOp f = foldr1 (.) <$> some f
operator "-" = lexeme . try $ string "-" <* notFollowedBy (char '>')
operator "/" = lexeme . try $ string "/" <* notFollowedBy (char '/')
operator "<" = lexeme . try $ string "<" <* notFollowedBy (char '=')
operator ">" = lexeme . try $ string ">" <* notFollowedBy (char '=')
operator n = symbol n
opWithLoc :: Text -> o -> (Ann SrcSpan o -> a) -> Parser a
opWithLoc name op f = do
Ann ann _ <- annotateLocation $ {- dbg (unpack name) $ -} operator name
return $ f (Ann ann op)
binaryN name op = (NBinaryDef name op NAssocNone,
InfixN (opWithLoc name op nBinary))
binaryL name op = (NBinaryDef name op NAssocLeft,
InfixL (opWithLoc name op nBinary))
binaryR name op = (NBinaryDef name op NAssocRight,
InfixR (opWithLoc name op nBinary))
prefix name op = (NUnaryDef name op,
Prefix (manyUnaryOp (opWithLoc name op nUnary)))
-- postfix name op = (NUnaryDef name op,
-- Postfix (opWithLoc name op nUnary))
nixOperators
:: Parser (Ann SrcSpan (NAttrPath NExprLoc))
-> [[(NOperatorDef, Operator Parser NExprLoc)]]
nixOperators selector =
[ -- This is not parsed here, even though technically it's part of the
-- expression table. The problem is that in some cases, such as list
-- membership, it's also a term. And since terms are effectively the
-- highest precedence entities parsed by the expression parser, it ends up
-- working out that we parse them as a kind of "meta-term".
-- {- 1 -} [ (NSpecialDef "." NSelectOp NAssocLeft,
-- Postfix $ do
-- sel <- seldot *> selector
-- mor <- optional (reserved "or" *> term)
-- return $ \x -> nSelectLoc x sel mor) ]
{- 2 -} [ (NBinaryDef " " NApp NAssocLeft,
-- Thanks to Brent Yorgey for showing me this trick!
InfixL $ nApp <$ symbol "") ]
, {- 3 -} [ prefix "-" NNeg ]
, {- 4 -} [ (NSpecialDef "?" NHasAttrOp NAssocLeft,
Postfix $ symbol "?" *> (flip nHasAttr <$> selector)) ]
, {- 5 -} [ binaryR "++" NConcat ]
, {- 6 -} [ binaryL "*" NMult
, binaryL "/" NDiv ]
, {- 7 -} [ binaryL "+" NPlus
, binaryL "-" NMinus ]
, {- 8 -} [ prefix "!" NNot ]
, {- 9 -} [ binaryR "//" NUpdate ]
, {- 10 -} [ binaryL "<" NLt
, binaryL ">" NGt
, binaryL "<=" NLte
, binaryL ">=" NGte ]
, {- 11 -} [ binaryN "==" NEq
, binaryN "!=" NNEq ]
, {- 12 -} [ binaryL "&&" NAnd ]
, {- 13 -} [ binaryL "||" NOr ]
, {- 14 -} [ binaryN "->" NImpl ]
]
data OperatorInfo = OperatorInfo
{ precedence :: Int
, associativity :: NAssoc
, operatorName :: Text
} deriving (Eq, Ord, Generic, Typeable, Data, Show)
getUnaryOperator :: NUnaryOp -> OperatorInfo
getUnaryOperator = (m Map.!) where
m = Map.fromList $ concat $ zipWith buildEntry [1..]
(nixOperators (error "unused"))
buildEntry i = concatMap $ \case
(NUnaryDef name op, _) -> [(op, OperatorInfo i NAssocNone name)]
_ -> []
getBinaryOperator :: NBinaryOp -> OperatorInfo
getBinaryOperator = (m Map.!) where
m = Map.fromList $ concat $ zipWith buildEntry [1..]
(nixOperators (error "unused"))
buildEntry i = concatMap $ \case
(NBinaryDef name op assoc, _) -> [(op, OperatorInfo i assoc name)]
_ -> []
getSpecialOperator :: NSpecialOp -> OperatorInfo
getSpecialOperator NSelectOp = OperatorInfo 1 NAssocLeft "."
getSpecialOperator o = m Map.! o where
m = Map.fromList $ concat $ zipWith buildEntry [1..]
(nixOperators (error "unused"))
buildEntry i = concatMap $ \case
(NSpecialDef name op assoc, _) -> [(op, OperatorInfo i assoc name)]
_ -> []