refactor: add ResultAggregate type

src/PostgREST/Query/SqlFragment.hs

@@ -7,12 +7,7 @@ Description : Helper functions for PostgREST.QueryBuilder.
 -}
 module PostgREST.Query.SqlFragment
   ( noLocationF
-  , asBinaryF
-  , asCsvF
-  , asGeoJsonF
-  , asJsonF
-  , asJsonSingleF
-  , asXmlF
+  , aggF
   , countF
   , fromQi
   , limitOffsetF
@@ -81,7 +76,8 @@ import PostgREST.RangeQuery              (NonnegRange, allRange,
                                           rangeLimit, rangeOffset)
 import PostgREST.SchemaCache.Identifiers (FieldName,
                                           QualifiedIdentifier (..))
-import PostgREST.SchemaCache.Routine     (Routine (..),
+import PostgREST.SchemaCache.Routine     (ResultAggregate (..),
+                                          Routine (..),
                                           funcReturnsScalar,
                                           funcReturnsSetOfScalar,
                                           funcReturnsSingleComposite)
@@ -208,14 +204,18 @@ asJsonF rout
       Just r  -> (funcReturnsSingleComposite r, funcReturnsScalar r, funcReturnsSetOfScalar r)
       Nothing -> (False, False, False)
 
-asXmlF :: FieldName -> SQL.Snippet
-asXmlF fieldName = "coalesce(xmlagg(_postgrest_t." <> pgFmtIdent fieldName <> "), '')"
+asXmlF :: Maybe FieldName -> SQL.Snippet
+asXmlF (Just fieldName) = "coalesce(xmlagg(_postgrest_t." <> pgFmtIdent fieldName <> "), '')"
+-- TODO unreachable because a previous step(binaryField) will validate that there's a field. This will be cleared once custom media types are implemented.
+asXmlF Nothing          = "coalesce(xmlagg(_postgrest_t), '')"
 
 asGeoJsonF ::  SQL.Snippet
 asGeoJsonF = "json_build_object('type', 'FeatureCollection', 'features', coalesce(json_agg(ST_AsGeoJSON(_postgrest_t)::json), '[]'))"
 
-asBinaryF :: FieldName -> SQL.Snippet
-asBinaryF fieldName = "coalesce(string_agg(_postgrest_t." <> pgFmtIdent fieldName <> ", ''), '')"
+asBinaryF :: Maybe FieldName -> SQL.Snippet
+asBinaryF (Just fieldName) = "coalesce(string_agg(_postgrest_t." <> pgFmtIdent fieldName <> ", ''), '')"
+-- TODO unreachable because a previous step(binaryField) will validate that there's a field. This will be cleared once custom media types are implemented.
+asBinaryF Nothing          = "coalesce(string_agg(_postgrest_t, ''), '')"
 
 locationF :: [Text] -> SQL.Snippet
 locationF pKeys = [qc|(
@@ -491,3 +491,13 @@ setConfigLocalJson prefix keyVals = [setConfigLocal mempty (prefix, gucJsonVal k
     gucJsonVal = LBS.toStrict . JSON.encode . HM.fromList . arrayByteStringToText
     arrayByteStringToText :: [(ByteString, ByteString)] -> [(Text,Text)]
     arrayByteStringToText keyVal = (T.decodeUtf8 *** T.decodeUtf8) <$> keyVal
+
+aggF :: Maybe Routine -> ResultAggregate -> SQL.Snippet
+aggF rout = \case
+  BuiltinAggJson          -> asJsonF rout
+  BuiltinAggSingleJson    -> asJsonSingleF rout
+  BuiltinAggGeoJson       -> asGeoJsonF
+  BuiltinAggCsv           -> asCsvF
+  BuiltinAggXml    bField -> asXmlF    bField
+  BuiltinAggBinary bField -> asBinaryF bField
+  NoAgg                   -> "''::text"