What I did:

Implemented recursive nexthop group enhancement in Orchagent (NhgOrch).
They have been proposed in:
sonic-net/SONiC#1636

Why I did it:

These changes are required to handle a new field - "nexthop_group" in the
App DB NEXT_HOP_GROUP_TABLE. Such nexthop groups are called recursive
nexthop groups. This field contains the list of member (singleton) nexthop groups.
Such recursive nexthop groups are represented by NEXT_HOP_GROUP objects.

tests/test_nhg.py

@@ -1550,22 +1550,6 @@ def create_route_inexistent_nhg_test():
         self.asic_db.wait_for_n_keys(self.ASIC_NHGM_STR, self.asic_nhgms_count)
 
     def test_nhgorch_nh_group(self, dvs, testlog):
-        # Test scenario:
-        # - create NHG 'group1' and assert it is being added to ASIC DB along with its members
-        def create_nhg_test():
-            # create next hop group in APPL DB
-            fvs = swsscommon.FieldValuePairs([('nexthop', '10.0.0.1,10.0.0.3,10.0.0.5'),
-                                            ("ifname", "Ethernet0,Ethernet4,Ethernet8")])
-            self.nhg_ps.set("group1", fvs)
-
-            # check if group was propagated to ASIC DB
-            self.asic_db.wait_for_n_keys(self.ASIC_NHG_STR, self.asic_nhgs_count + 1)
-            assert self.nhg_exists('group1')
-
-            # check if members were propagated to ASIC DB
-            self.asic_db.wait_for_n_keys(self.ASIC_NHGM_STR, self.asic_nhgms_count + 3)
-            assert len(self.get_nhgm_ids('group1')) == 3
-
         # Test scenario:
         # - create recursive nhg - rec_grp1 with two members - grp1 and grp2 only one of which exists
         # - create singleton nhg grp2 and check if the rec_grp1 is updated with both the members
@@ -1617,7 +1601,7 @@ def create_recursive_nhg_test():
 
             # check that the group was not propagated to ASIC DB
             self.asic_db.wait_for_n_keys(self.ASIC_NHG_STR, self.asic_nhgs_count + 1)
-            assert self.nhg_exists('rec_grp2')
+            assert not self.nhg_exists('rec_grp2')
 
             self.nhg_ps._del("rec_grp2")
             self.nhg_ps._del("rec_grp1")
@@ -1627,6 +1611,22 @@ def create_recursive_nhg_test():
             self.asic_db.wait_for_n_keys(self.ASIC_NHG_STR, self.asic_nhgs_count)
             self.asic_db.wait_for_n_keys(self.ASIC_NHGM_STR, self.asic_nhgms_count)
 
+        # Test scenario:
+        # - create NHG 'group1' and assert it is being added to ASIC DB along with its members
+        def create_nhg_test():
+            # create next hop group in APPL DB
+            fvs = swsscommon.FieldValuePairs([('nexthop', '10.0.0.1,10.0.0.3,10.0.0.5'),
+                                            ("ifname", "Ethernet0,Ethernet4,Ethernet8")])
+            self.nhg_ps.set("group1", fvs)
+
+            # check if group was propagated to ASIC DB
+            self.asic_db.wait_for_n_keys(self.ASIC_NHG_STR, self.asic_nhgs_count + 1)
+            assert self.nhg_exists('group1')
+
+            # check if members were propagated to ASIC DB
+            self.asic_db.wait_for_n_keys(self.ASIC_NHGM_STR, self.asic_nhgms_count + 3)
+            assert len(self.get_nhgm_ids('group1')) == 3
+
         # Test scenario:
         # - create a route pointing to `group1` and assert it is being added to ASIC DB and pointing to its SAI ID
         # - delete the route and assert it is being removed
@@ -1781,6 +1781,7 @@ def update_nhgm_count_test():
 
         self.init_test(dvs, 4)
 
+        create_recursive_nhg_test()
         create_nhg_test()
         create_route_nhg_test()
         link_flap_test()