Add the parseTsvWithDiagnostics function

This will pave the way for a more thorough refactoring to
be able to emit diagnostics after parsing.

src/Gargantext/Core/Text/Corpus/Parsers/TSV.hs

+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE ViewPatterns #-}
 {-|
 Module      : Gargantext.Core.Text.Corpus.Parsers.TSV
 Description :
@@ -31,6 +34,7 @@ import Gargantext.Core.Text.Context ( splitBy, SplitContext(..) )
 import Gargantext.Database.Admin.Types.Hyperdata.Document ( HyperdataDocument(..) )
 import Gargantext.Prelude hiding (length, show)
 import Protolude
+import qualified Data.ByteString as B
 
 ---------------------------------------------------------------
 headerTsvGargV3 :: Header
@@ -406,7 +410,37 @@ readTSVFile fp = do
     Left _err -> pure $ Left _err
     Right del -> pure $ readTsvLazyBS del file
 
-
+-- | Allows the parser to report errors happening at a given row in the document.
+data AtRow a = AtRow Int a
+
+data ParseTsvResult a
+  = ParseTsvResult
+  { _ptr_parsed_records  :: a
+  , _ptr_skipped_records :: [ AtRow (Text, Vector ByteString) ]
+  }
+
+parseTsvWithDiagnostics :: Delimiter
+                        -> BL.ByteString
+                        -> Either Text (ParseTsvResult [TsvDoc])
+parseTsvWithDiagnostics d bs = case decodeWith @Record (tsvDecodeOptions d) HasHeader bs of
+  Left err         -> Left  $ pack err
+  Right rawRecords -> Right $ uncurry ParseTsvResult . first reverse $
+    foldl' parse_raw_record (mempty, mempty) (zip (V.toList rawRecords) [ 1 .. ])
+  where
+    parse_raw_record :: ([TsvDoc], [AtRow (Text, Vector ByteString)])
+                      -> (Vector ByteString, Int)
+                      -> ([TsvDoc], [AtRow (Text, Vector ByteString)])
+    parse_raw_record (!succeeded, !failed) (input_record, current_row) =
+      case decodeByNameWith @TsvDoc (tsvDecodeOptions d) (intercalateRecords d input_record) of
+        Left err                        -> (succeeded, AtRow current_row (pack err, input_record) : failed)
+        Right (_, V.toList -> [tsvDoc]) -> (tsvDoc : succeeded, failed)
+        -- The one below won't happen, but it's left for completeness.
+        Right (_, V.toList -> tsvDocs) -> (tsvDocs <> succeeded, failed)
+
+-- | \"Reconstructs\" a line out of a parsed record, so that it can be fed back
+-- into the invidual parser.
+intercalateRecords :: Delimiter -> Record -> BL.ByteString
+intercalateRecords d r = BL.fromStrict $ B.intercalate (B.pack [delimiter d]) (V.toList r)
 
 -- | TODO use readByteStringLazy
 readTsvLazyBS :: Delimiter