fix, using .:? instead of .: for more flexibility

src/HAL/Doc/Corpus.hs

@@ -43,7 +43,7 @@ instance FromJSON Corpus where
     _corpus_source               <- o .:? "source_s"
     _corpus_authors_names        <- o .: "authFullName_s" <|> return []
 
-    idsNames <- o .: "structIdName_fs" :: Parser [Text] --unsparsed (contains a _FacetSep_)
+    idsNames <- o .:? "structIdName_fs" :: Parser (Maybe [Text]) --unsparsed (contains a _FacetSep_)
 
     let structIdname = getStructIdsNames idsNames
 
@@ -64,11 +64,12 @@ instance FromJSON Corpus where
 -- > StructId_FacetSep_StructName
 -- 
 -- returns [(StructId, StructName)]
-getStructIdsNames :: [T.Text] -> [(Int, T.Text)]
-getStructIdsNames idsNames = map (\tab -> (P.read (T.unpack (P.head tab)) :: Int, P.last tab)) $ splitInstitutes idsNames
+getStructIdsNames :: Maybe [T.Text] -> [(Int, T.Text)]
+getStructIdsNames (Just idsNames) = map (\tab -> (P.read (T.unpack (P.head tab)) :: Int, P.last tab)) $ splitInstitutes idsNames
   where
     splitInstitutes :: [T.Text] -> [[T.Text]]
     splitInstitutes = P.map (T.splitOn (T.pack "_FacetSep_"))
+getStructIdsNames Nothing = []
 
 instance ToHttpApiData Corpus where
   toUrlPiece _ = "docid,title_s,en_abstract_s,fr_abstract_s,submittedDate_s,source_s,authFullName_s,structId_i,structIdName_fs"