program is runnable again, File doesn't backtrack out of import anymore

app/Main.hs

@@ -1,10 +1,32 @@
-module Main (main) where
+module Main 
+( main
+) where
+
+import System.Directory as Directory
+import qualified Control.Monad.Trans.Reader as Reader
+
+import qualified Data.Set as Set
+
 import qualified Text.Parsec as Parsec
+
+import qualified Path as Path
+
+import Ubc.Parse.Syntax.Config (Config(..))
+
 import qualified Ubc.Parse.Syntax.File as File
 
+minimalConfig :: IO Config
+minimalConfig = do
+        workingDir <- Directory.getCurrentDirectory >>= Path.parseAbsDir
+        pure $ Config (Set.singleton workingDir)
+
 main :: IO ()
 main = do
         text <- getContents
         -- fixme: handle errors?
 
-        print $ Parsec.parse (File.parse "<stdin>" <* Parsec.eof) "<stdin>" text 
+        parseConfig <- minimalConfig
+
+        result <- Reader.runReaderT (Parsec.runPT (File.parse <* Parsec.eof) () "<stdin>" text) parseConfig
+        print $ result
+--      print $ Parsec.parse (File.parse <* Parsec.eof) "<stdin>" text

src/Ubc/Parse/Syntax/File.hs

@@ -26,6 +26,7 @@ import qualified Ubc.Parse.Syntax.Struct as Struct
 import qualified Ubc.Parse.Syntax.Function as Function
 import qualified Ubc.Parse.Syntax.Statement as Statement
 import qualified Ubc.Parse.Syntax.Enumeration as Enumeration
+import qualified Text.Parsec as Parsec
 
 data File = File
         { name :: String
@@ -44,8 +45,11 @@ data FileBody = FileBody
         deriving (Semigroup, Monoid) via Generically FileBody
 -- dont use `deriving ... via FileBody` because that leads to a loop, somehow
 
-parse :: String -> ParsecT String u Transformer File
+parse :: ParsecT String u Transformer File
-parse source = File source <$!> mconcat <$!> many fileMember
+parse = do
+        fileName <- Parsec.sourceName <$!> Parsec.getPosition
+        fileBody <- mconcat <$!> many fileMember
+        pure $ File fileName fileBody
 
 fileMember :: ParsecT String u Transformer FileBody
 fileMember = choice

src/Ubc/Parse/Syntax/File.hs-boot

@@ -0,0 +1,15 @@
+module Ubc.Parse.Syntax.File
+( File
+, parse
+)
+where
+
+import Text.Parsec (ParsecT)
+
+import Ubc.Parse.Syntax (Transformer)
+
+data File 
+instance Show File
+
+parse :: ParsecT String u Transformer File
+

src/Ubc/Parse/Syntax/Import.hs

@@ -54,7 +54,6 @@ parse :: ParsecT String u Transformer Import
 parse = do
         UbcLanguage.reserved "import"
         fragments <- importPath
-        importAs <- option (NonEmpty.last fragments) importAlias
 
         -- concatenate directory and file parts, also utf-decoding
         relFile <- case parseRelPath fragments of
@@ -66,12 +65,16 @@ parse = do
         -- only existing files
         existingFiles <- liftIO $ filterInexistent possiblePaths
 
-        -- fail if there are multiple files
+        -- fail or parse
-        case existingFiles of
+        importedFile <- case existingFiles of
                 [] -> fail $ notFoundMessage relFile possiblePaths
-                [path] -> parseFile path importAs
+                [path] -> parseFile path
                 fs@_ -> fail $ multipleFoundMessage relFile fs
 
+        importAs <- Parsec.parserTraced "alias" $ option (NonEmpty.last fragments) importAlias
+
+        return $ Import importedFile importAs
+
 importAlias :: Monad m => ParsecT String u m String
 importAlias = UbcLanguage.reserved "as" 
         *> UbcLanguage.identifier
@@ -82,12 +85,12 @@ multipleFoundMessage relFile foundFiles = "Could not identify imported file " <>
         <> (unlines . List.map (Path.fromAbsFile >>> ('\t':)) $ foundFiles)
 
 notFoundMessage :: Path Rel File -> [Path Abs File] -> String
-notFoundMessage relFile searchedLocations = "Could not locate import file path" <> Path.fromRelFile relFile <> "\n"
+notFoundMessage relFile searchedLocations = "Could not locate import file <" <> Path.fromRelFile relFile <> ">\n"
-                <> "Searched locations were:"
+                <> "Searched locations were:\n"
                 <> (unlines . List.map (('\t':) . Path.fromAbsFile) $ searchedLocations)
 
-parseFile :: Path Abs File -> String -> ParsecT String u Transformer Import
+parseFile :: Path Abs File -> ParsecT String u Transformer File.File
-parseFile path importAs = do
+parseFile path = do
         let stringPath = Path.fromAbsFile path
         contents <- liftIO . readFile $ stringPath
 
@@ -101,16 +104,21 @@ parseFile path importAs = do
                 >>> (flip Parsec.setSourceColumn) 1
                 $ oldPosition
 
+        -- disable backtracking (consuming input)
+        Parsec.setInput "_" <* Parsec.char '_'
+
         -- prepare new state
         Parsec.setInput contents
         Parsec.setPosition newPosition
-        importedFile <- File.parse stringPath 
+
+        -- parse the file
+        importedFile <- File.parse <* Parsec.eof
 
         -- restore old state
         Parsec.setInput oldInput
         Parsec.setPosition oldPosition
 
-        pure $ Import importedFile importAs
+        pure importedFile 
 
 parseRelPath :: MonadThrow m => NonEmpty FilePath -> m (Path Rel File)
 parseRelPath fragments = do

src/Ubc/Parse/Syntax/Import.hs-boot

@@ -0,0 +1,15 @@
+module Ubc.Parse.Syntax.Import
+( Import
+, parse
+)
+where
+
+import Text.Parsec (ParsecT)
+
+import Ubc.Parse.Syntax (Transformer)
+
+data Import 
+instance Show Import
+
+parse :: ParsecT String u Transformer Import
+