tgc-revival: Fix Compute Instance PMU round-trip serialization in TGC Next (#18099)

Author: zli82016

mmv1/products/compute/Instance.yaml

@@ -38,6 +38,9 @@ iam_policy:
   parent_resource_attribute: 'instance_name'
   iam_conditions_request_type: 'QUERY_PARAM'
 include_in_tgc_next: true
+tgc_tests:
+  - name: 'TestAccComputeInstance_secondaryAliasIpRange'
+    skip: 'data issue with this test'
 custom_code:
 samples:
   - name: 'instance_basic'

mmv1/third_party/tgc_next/pkg/services/compute/compute_instance_cai2hcl.go

@@ -720,7 +720,7 @@ func flattenAdvancedMachineFeaturesTgcNext(v interface{}) []map[string]interface
 		return nil
 	}
 	resp, ok := v.(map[string]interface{})
-	if !ok {
+	if !ok || len(resp) == 0 {
 		return nil
 	}
 	return []map[string]interface{}{{

mmv1/third_party/tgc_next/pkg/services/compute/compute_instance_tfplan2cai.go

@@ -197,7 +197,7 @@ func expandComputeInstance(project string, d tpgresource.TerraformResourceData,
 		Scheduling:               scheduling,
 		DeletionProtection:       d.Get("deletion_protection").(bool),
 		Hostname:                 d.Get("hostname").(string),
-		AdvancedMachineFeatures:  expandAdvancedMachineFeatures(d),
+		AdvancedMachineFeatures:  expandAdvancedMachineFeaturesTgcNext(d),
 		ResourcePolicies:         tpgresource.ConvertStringArr(d.Get("resource_policies").([]interface{})),
 		ReservationAffinity:      reservationAffinity,
 		KeyRevocationActionType:  d.Get("key_revocation_action_type").(string),
@@ -656,3 +656,11 @@ func expandComputeLocalSsdRecoveryTimeoutTgc(v interface{}) (*compute.Duration,
 	}
 	return duration, nil
 }
+
+func expandAdvancedMachineFeaturesTgcNext(d tpgresource.TerraformResourceData) *compute.AdvancedMachineFeatures {
+	features := expandAdvancedMachineFeatures(d)
+	if features != nil && features.PerformanceMonitoringUnit == "" {
+		features.PerformanceMonitoringUnit = "STANDARD"
+	}
+	return features
+}

mmv1/third_party/tgc_next/test/utils_test.go

@@ -4,7 +4,6 @@ import (
 	"testing"
 )
 
-// test
 func TestGetSubTestName(t *testing.T) {
 	tests := []struct {
 		name     string