Don't rewrite floats and don't break e+ syntax

src/Nixfmt/Parser/Float.hs

@@ -1,66 +1,33 @@
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 
 module Nixfmt.Parser.Float (floatParse) where
 
-import "base" Control.Monad (void)
-import qualified "base" Data.Char as Char
-import "base" Data.Foldable (foldl')
-import "base" Data.Proxy (Proxy (..))
-import "megaparsec" Text.Megaparsec (
+import Data.List (singleton)
+import Data.Text (Text, pack)
+import Text.Megaparsec (
   MonadParsec,
   Token,
-  chunkToTokens,
-  notFollowedBy,
+  many,
+  oneOf,
   option,
-  takeWhile1P,
+  satisfy,
+  some,
   try,
-  (<?>),
   (<|>),
  )
-import "megaparsec" Text.Megaparsec.Char (char, char', digitChar)
-import "megaparsec" Text.Megaparsec.Char.Lexer (decimal, signed)
-import "scientific" Data.Scientific (scientific, toRealFloat)
+import Text.Megaparsec.Char (char, digitChar)
 
--- copied (and modified) from Text.Megaparsec.Char.Lexer
-data SP = SP !Integer {-# UNPACK #-} !Int
-
-floatParse :: (MonadParsec e s m, Token s ~ Char, RealFloat a) => m a
-floatParse = do
-  notFollowedBy $ char '0' >> digitChar
-  notFollowedBy (char' 'e')
-  c' <- (decimal <?> "decimal") <|> return 0
-  toRealFloat
-    <$> ( ( do
-              SP c e' <- dotDecimal_ c'
-              e <- option e' (try $ exponent_ e')
-              return (scientific c e)
+floatParse :: (MonadParsec e s m, Token s ~ Char, Semigroup (m [Char])) => m Text
+floatParse =
+  -- This mirrors https://github.com/NixOS/nix/blob/b89eca9aecc69d4dfc0f0afd9353c126eb7b5858/src/libexpr/lexer.l#L96
+  pack
+    <$> ( ( try oneThroughNineStart
+              <|> zeroDotStart
           )
-            <|> (scientific c' <$> exponent_ 0)
+            <> scientific
         )
-{-# INLINE floatParse #-}
-
--- copied from Text.Megaparsec.Char.Lexer
-dotDecimal_ ::
-  forall e s m.
-  (MonadParsec e s m, Token s ~ Char) =>
-  Integer ->
-  m SP
-dotDecimal_ c' = do
-  void (char '.')
-  let mkNum = foldl' step (SP c' 0) . chunkToTokens @s Proxy
-      step (SP a e') c =
-        SP
-          (a * 10 + fromIntegral (Char.digitToInt c))
-          (e' - 1)
-  mkNum <$> takeWhile1P (Just "digit") Char.isDigit
-{-# INLINE dotDecimal_ #-}
-
--- copied from Text.Megaparsec.Char.Lexer
-exponent_ :: (MonadParsec e s m, Token s ~ Char) => Int -> m Int
-exponent_ e' = do
-  void (char' 'e')
-  (+ e') <$> signed (return ()) decimal
-{-# INLINE exponent_ #-}
+  where
+    oneThroughNineStart = oneThroughNine <> many digitChar <> (singleton <$> char '.') <> many digitChar
+    zeroDotStart = option "" (singleton <$> char '0') <> (singleton <$> char '.') <> some digitChar
+    scientific = option "" ((singleton <$> oneOf "Ee") <> option "" (singleton <$> oneOf "+-") <> some digitChar)
+    oneThroughNine = singleton <$> satisfy (\c -> '1' <= c && c <= '9')

src/Nixfmt/Types.hs

@@ -488,7 +488,7 @@ instance (LanguageElement a) => LanguageElement (NonEmpty a) where
 
 data Token
   = Integer Int
-  | Float Double
+  | Float Text
   | Identifier Text
   | EnvPath Text
   | KAssert
@@ -588,7 +588,7 @@ operators =
 tokenText :: Token -> Text
 tokenText (Identifier i) = i
 tokenText (Integer i) = pack (show i)
-tokenText (Float f) = pack (show f)
+tokenText (Float f) = f
 tokenText (EnvPath p) = "<" <> p <> ">"
 tokenText KAssert = "assert"
 tokenText KElse = "else"

test/correct/numbers.nix

@@ -0,0 +1,23 @@
+[
+  (-9223372036854775807)
+  (-1)
+  0
+  1
+  # 01
+  # 0000000000000000000000000000000000000000000001
+  9223372036854775807
+
+  .1
+  0.1
+  1.0
+  .1e0
+  1.0e0
+  1.e0
+  .1e-0
+  1.0e-0
+  1.e-0
+  .1e+0
+  1.0e+0
+  1.e+0
+
+]

test/diff/operator-after-operator/out-pure.nix

@@ -1,2 +1,2 @@
 # https://github.com/NixOS/nixfmt/issues/122
-(1 + 1) (1 + 0.4)
+(1 + 1) (1 + .4)

test/diff/operator-after-operator/out.nix

@@ -1,2 +1,2 @@
 # https://github.com/NixOS/nixfmt/issues/122
-(1 + 1) (1 + 0.4)
+(1 + 1) (1 + .4)