fix: Avoid inconsistent result after apply when transitioning from replica set to sharded

internal/service/advancedcluster/resource_advanced_cluster_migration_test.go

@@ -52,9 +52,10 @@ func TestMigAdvancedCluster_replicaSetAWSProviderUpdate(t *testing.T) {
 		Steps: []resource.TestStep{
 			{
 				ExternalProviders: acc.ExternalProviders(versionBeforeISSRelease),
-				Config: configReplicaSetAWSProvider(t, false, ReplicaSetAWSConfig{
+				Config: configAWSProvider(t, false, ReplicaSetAWSConfig{
 					ProjectID:          projectID,
 					ClusterName:        clusterName,
+					ClusterType:        "REPLICASET",
 					DiskSizeGB:         60,
 					NodeCountElectable: 3,
 					WithAnalyticsSpecs: true,
@@ -63,9 +64,10 @@ func TestMigAdvancedCluster_replicaSetAWSProviderUpdate(t *testing.T) {
 			},
 			{
 				ProtoV6ProviderFactories: acc.TestAccProviderV6Factories,
-				Config: configReplicaSetAWSProvider(t, false, ReplicaSetAWSConfig{
+				Config: configAWSProvider(t, false, ReplicaSetAWSConfig{
 					ProjectID:          projectID,
 					ClusterName:        clusterName,
+					ClusterType:        "REPLICASET",
 					DiskSizeGB:         60,
 					NodeCountElectable: 5,
 					WithAnalyticsSpecs: true,

internal/service/advancedcluster/resource_advanced_cluster_test.go

@@ -203,25 +203,38 @@ func replicaSetAWSProviderTestCase(t *testing.T, isAcc bool) resource.TestCase {
 		CheckDestroy:             acc.CheckDestroyCluster,
 		Steps: []resource.TestStep{
 			{
-				Config: configReplicaSetAWSProvider(t, isAcc, ReplicaSetAWSConfig{
+				Config: configAWSProvider(t, isAcc, ReplicaSetAWSConfig{
 					ProjectID:          projectID,
 					ClusterName:        clusterName,
+					ClusterType:        "REPLICASET",
 					DiskSizeGB:         60,
 					NodeCountElectable: 3,
 					WithAnalyticsSpecs: true,
 				}),
 				Check: checkReplicaSetAWSProvider(isAcc, projectID, clusterName, 60, 3, true, true),
 			},
 			{
-				Config: configReplicaSetAWSProvider(t, isAcc, ReplicaSetAWSConfig{
+				Config: configAWSProvider(t, isAcc, ReplicaSetAWSConfig{
 					ProjectID:          projectID,
 					ClusterName:        clusterName,
+					ClusterType:        "REPLICASET",
 					DiskSizeGB:         50,
 					NodeCountElectable: 5,
 					WithAnalyticsSpecs: false, // removed as part of other updates, computed value is expected to be the same
 				}),
 				Check: checkReplicaSetAWSProvider(isAcc, projectID, clusterName, 50, 5, true, true),
 			},
+			{ // testing transition from replica set to sharded cluster
+				Config: configAWSProvider(t, isAcc, ReplicaSetAWSConfig{
+					ProjectID:          projectID,
+					ClusterName:        clusterName,
+					ClusterType:        "SHARDED",
+					DiskSizeGB:         50,
+					NodeCountElectable: 5,
+					WithAnalyticsSpecs: false,
+				}),
+				Check: checkReplicaSetAWSProvider(isAcc, projectID, clusterName, 50, 5, true, true),
+			},
 			acc.TestStepImportCluster(resourceName, "replication_specs", "retain_backups_enabled"),
 		},
 	}
@@ -1772,12 +1785,13 @@ func checkKeyValueBlocksPreviewProviderV2(isAcc, includeDataSources bool, blockN
 type ReplicaSetAWSConfig struct {
 	ProjectID          string
 	ClusterName        string
+	ClusterType        string
 	DiskSizeGB         int
 	NodeCountElectable int
 	WithAnalyticsSpecs bool
 }
 
-func configReplicaSetAWSProvider(t *testing.T, isAcc bool, configInfo ReplicaSetAWSConfig) string {
+func configAWSProvider(t *testing.T, isAcc bool, configInfo ReplicaSetAWSConfig) string {
 	t.Helper()
 	analyticsSpecs := ""
 	if configInfo.WithAnalyticsSpecs {
@@ -1791,24 +1805,24 @@ func configReplicaSetAWSProvider(t *testing.T, isAcc bool, configInfo ReplicaSet
 		resource "mongodbatlas_advanced_cluster" "test" {
 			project_id   = %[1]q
 			name         = %[2]q
-			cluster_type = "REPLICASET"
+			cluster_type = %[3]q
 			retain_backups_enabled = "true"
-			disk_size_gb = %[3]d
+			disk_size_gb = %[4]d
 
 			replication_specs {
 				region_configs {
 					electable_specs {
 						instance_size = "M10"
-						node_count    = %[4]d
+						node_count    = %[5]d
 					}
-					%[5]s
+					%[6]s
 					provider_name = "AWS"
 					priority      = 7
 					region_name   = "US_WEST_2"
 				}
 			}
 		}
-	`, configInfo.ProjectID, configInfo.ClusterName, configInfo.DiskSizeGB, configInfo.NodeCountElectable, analyticsSpecs)) + dataSourcesTFOldSchema
+	`, configInfo.ProjectID, configInfo.ClusterName, configInfo.ClusterType, configInfo.DiskSizeGB, configInfo.NodeCountElectable, analyticsSpecs)) + dataSourcesTFOldSchema
 }
 
 func checkReplicaSetAWSProvider(isAcc bool, projectID, name string, diskSizeGB, nodeCountElectable int, checkDiskSizeGBInnerLevel, checkExternalID bool) resource.TestCheckFunc {

internal/service/advancedclustertpf/plan_modifier.go

@@ -19,6 +19,7 @@ var (
 		"replication_specs":      {},
 		"mongo_db_major_version": {"mongo_db_version"},
 		"tls_cipher_config_mode": {"custom_openssl_cipher_config_tls12"},
+		"cluster_type":           {"config_server_management_mode", "config_server_type"}, // computed values of config server change when REPLICA_SET changes to SHARDED
 	}
 	attributeReplicationSpecChangeMapping = map[string][]string{
 		// All these fields can exist in specs that are computed, therefore, it is not safe to use them when they have changed.