fix: Stricter query string parsing - no empty fts lang

Signed-off-by: Wolfgang Walther <walther@technowledgy.de>

CHANGELOG.md

@@ -29,7 +29,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
  - #2444, Removed `db-pool-timeout` option, because this was removed upstream in hasql-pool. - @robx
  - #2343, PATCH requests that don't affect any rows no longer return 404 - @wolfgangwalther
- - #2537, Stricter parsing of query string. Instead of silently ignoring, the parser now throws on invalid syntax like json paths for embeddings, hints for regular columns, empty casts, etc. - @wolfgangwalther
+ - #2537, Stricter parsing of query string. Instead of silently ignoring, the parser now throws on invalid syntax like json paths for embeddings, hints for regular columns, empty casts or fts languages, etc. - @wolfgangwalther
 
 ### Deprecated
 

src/PostgREST/ApiRequest/QueryParams.hs

@@ -518,6 +518,12 @@ pFieldSelect = lexeme $
            try (void $ lookAhead (string ",")) <|>
            try eof
 
+-- |
+-- Parse operator expression used in horizontal filtering
+--
+-- >>> P.parse (pOpExpr pSingleVal) "" "fts().value"
+-- Left (line 1, column 7):
+-- unknown single value operator fts()
 pOpExpr :: Parser SingleVal -> Parser OpExpr
 pOpExpr pSVal = try ( string "not" *> pDelimiter *> (OpExpr True <$> pOperation)) <|> OpExpr False <$> pOperation
   where
@@ -541,7 +547,7 @@ pOpExpr pSVal = try ( string "not" *> pDelimiter *> (OpExpr True <$> pOperation)
     pFts = do
       opStr <- try (P.many (noneOf ".("))
       op <- parseMaybe ("unknown fts operator " <> opStr) . ftsOperator $ toS opStr
-      lang <- optionMaybe $ try (between (char '(') (char ')') $ many pIdentifierChar)
+      lang <- optionMaybe $ try (between (char '(') (char ')') $ many1 pIdentifierChar)
       pDelimiter >> Fts op (toS <$> lang) <$> pSVal
 
     parseMaybe :: [Char] -> Maybe a -> Parser a