server/mssql: fix table_by_pk query returning empty array

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/2810
GitOrigin-RevId: ed8e694d491d7bd28da0b39da2b1f1150d2e3735

CHANGELOG.md

@@ -9,6 +9,8 @@
 ### Bug fixes and improvements
 (Add entries below in the order of server, console, cli, docs, others)
 
+- server: fix mssql `table_by_pk` query returning empty array (fix #7784)
+
 ## v2.1.0-beta.2
 
 ### Action transforms

server/src-lib/Hasura/Backends/MSSQL/ToQuery.hs

@@ -496,12 +496,23 @@ parens p = "(" <+> IndentPrinter 1 p <+> ")"
 
 -- | Wrap a select with things needed when using FOR JSON.
 wrapFor :: For -> Printer -> Printer
-wrapFor for' inner = nullToArray
+wrapFor for' inner = coalesceNull
   where
-    nullToArray =
+    coalesceNull =
       case for' of
         NoFor -> rooted
-        JsonFor _ -> SeqPrinter ["SELECT ISNULL((", rooted, "), '[]')"]
+        JsonFor forJson ->
+          SeqPrinter
+            [ "SELECT ISNULL((",
+              rooted,
+              "), '",
+              emptyarrayOrNull forJson,
+              "')"
+            ]
+    emptyarrayOrNull ForJson {..} =
+      case jsonCardinality of
+        JsonSingleton -> "null"
+        JsonArray -> "[]"
     rooted =
       case for' of
         JsonFor ForJson {jsonRoot, jsonCardinality = JsonSingleton} ->

server/tests-py/queries/graphql_query/basic/select_query_author_by_pkey_null.yaml

@@ -0,0 +1,14 @@
+description: select query on author with id = 4
+url: /v1/graphql
+status: 200
+response:
+  data:
+    author_by_pk: null
+query:
+  query: |
+    query {
+      author_by_pk(id: 4){
+        id
+        name
+      }
+    }

server/tests-py/test_graphql_queries.py

@@ -306,7 +306,6 @@ class TestGraphQLQueryBasicCommon:
     def test_select_query_multiple_columns_obj_fkey(self, hge_ctx, transport):
         check_query_f(hge_ctx, self.dir() + "/select_multiple_columns_obj_fkey.yaml", transport)
 
-
     @classmethod
     def dir(cls):
         return 'queries/graphql_query/basic'
@@ -331,6 +330,12 @@ class TestGraphQLQueryBasicMSSQL:
     def test_nodes_aggregates_conditions_mssql(self, hge_ctx, transport):
         check_query_f(hge_ctx, self.dir() + "/nodes_aggregates_conditions_mssql.yaml", transport)
 
+    def test_select_query_author_pk(self, hge_ctx, transport):
+        check_query_f(hge_ctx, self.dir() + '/select_query_author_by_pkey.yaml', transport)
+
+    def test_select_query_author_pk_null(self, hge_ctx, transport):
+        check_query_f(hge_ctx, self.dir() + '/select_query_author_by_pkey_null.yaml', transport)
+
     @classmethod
     def dir(cls):
         return 'queries/graphql_query/basic'
@@ -344,12 +349,6 @@ class TestGraphQLQueryBasicPostgres:
     def test_select_various_postgres_types(self, hge_ctx, transport):
         check_query_f(hge_ctx, self.dir() + '/select_query_test_types_postgres.yaml', transport)
 
-    # TODO: https://github.com/hasura/graphql-engine-mono/issues/866
-    # This test currently fails on MSSQL.
-    # Move to TestGraphQLQueryBasicCommon once linked issue is fixed.
-    def test_select_query_author_pk(self, hge_ctx, transport):
-        check_query_f(hge_ctx, self.dir() + '/select_query_author_by_pkey.yaml', transport)
-
     def test_select_query_invalid_escape_sequence(self, hge_ctx, transport):
         transport = 'http'
         check_query_f(hge_ctx, self.dir() + "/select_query_invalid_escape_sequence.yaml", transport)
@@ -384,6 +383,12 @@ class TestGraphQLQueryBasicPostgres:
         assert st_code == 400, resp
         assert resp['error'] == "Expecting object { table, columns }."
 
+    def test_select_query_author_pk(self, hge_ctx, transport):
+        check_query_f(hge_ctx, self.dir() + '/select_query_author_by_pkey.yaml', transport)
+
+    def test_select_query_author_pk_null(self, hge_ctx, transport):
+        check_query_f(hge_ctx, self.dir() + '/select_query_author_by_pkey_null.yaml', transport)
+
     @classmethod
     def dir(cls):
         return 'queries/graphql_query/basic'