Fix error that occured in e2e test

cli/gcp/client/network.go

@@ -124,7 +124,7 @@ func (c *Client) TerminateVPCs(ctx context.Context) error {
 		return errors.New("client has firewalls, which must be deleted first")
 	}
 
-	if err := c.terminateSubnets(ctx); err != nil {
+	if err := c.terminateSubnet(ctx); err != nil {
 		return err
 	}
 
@@ -183,23 +183,18 @@ func (c *Client) createSubnet(ctx context.Context, name, cidr, network, secondar
 	return c.subnetworksAPI.Insert(ctx, req)
 }
 
-func (c *Client) terminateSubnets(ctx context.Context) error {
+func (c *Client) terminateSubnet(ctx context.Context) error {
-	var op Operation
+	if c.subnetwork == "" {
-	var err error
+		return nil
-	if c.subnetwork != "" {
-		op, err = c.terminateSubnet(ctx, c.subnetwork)
-		if err != nil {
-			return err
-		}
 	}
-	return c.waitForOperations(ctx, []Operation{op})
-}
-
-func (c *Client) terminateSubnet(ctx context.Context, name string) (Operation, error) {
 	req := &computepb.DeleteSubnetworkRequest{
 		Project:    c.project,
 		Region:     c.region,
-		Subnetwork: name,
+		Subnetwork: c.subnetwork,
 	}
-	return c.subnetworksAPI.Delete(ctx, req)
+	op, err := c.subnetworksAPI.Delete(ctx, req)
+	if err != nil {
+		return err
+	}
+	return c.waitForOperations(ctx, []Operation{op})
 }

cli/gcp/client/network_test.go

@@ -97,6 +97,7 @@ func TestTerminateVPCs(t *testing.T) {
 		networksAPI        networksAPI
 		subnetworksAPI     subnetworksAPI
 		firewalls          []string
+		subnetwork         string
 		wantErr            bool
 	}{
 		"successful terminate": {
@@ -104,6 +105,14 @@ func TestTerminateVPCs(t *testing.T) {
 			operationRegionAPI: stubOperationRegionAPI{},
 			networksAPI:        stubNetworksAPI{},
 			subnetworksAPI:     stubSubnetworksAPI{},
+			subnetwork:         "subnetwork-id-1",
+		},
+		"subnetwork empty": {
+			operationGlobalAPI: stubOperationGlobalAPI{},
+			operationRegionAPI: stubOperationRegionAPI{},
+			networksAPI:        stubNetworksAPI{},
+			subnetworksAPI:     stubSubnetworksAPI{},
+			subnetwork:         "",
 		},
 		"failed wait global op": {
 			operationGlobalAPI: stubOperationGlobalAPI{waitErr: someErr},
@@ -111,6 +120,7 @@ func TestTerminateVPCs(t *testing.T) {
 			networksAPI:        stubNetworksAPI{},
 			subnetworksAPI:     stubSubnetworksAPI{},
 			wantErr:            true,
+			subnetwork:         "subnetwork-id-1",
 		},
 		"failed delete networks": {
 			operationGlobalAPI: stubOperationGlobalAPI{},
@@ -118,6 +128,7 @@ func TestTerminateVPCs(t *testing.T) {
 			networksAPI:        stubNetworksAPI{deleteErr: someErr},
 			subnetworksAPI:     stubSubnetworksAPI{},
 			wantErr:            true,
+			subnetwork:         "subnetwork-id-1",
 		},
 		"failed delete subnetworks": {
 			operationGlobalAPI: stubOperationGlobalAPI{},
@@ -125,6 +136,7 @@ func TestTerminateVPCs(t *testing.T) {
 			networksAPI:        stubNetworksAPI{},
 			subnetworksAPI:     stubSubnetworksAPI{deleteErr: someErr},
 			wantErr:            true,
+			subnetwork:         "subnetwork-id-1",
 		},
 		"must delete firewalls first": {
 			firewalls:          []string{"firewall-1", "firewall-2"},
@@ -133,6 +145,7 @@ func TestTerminateVPCs(t *testing.T) {
 			networksAPI:        stubNetworksAPI{},
 			subnetworksAPI:     stubSubnetworksAPI{},
 			wantErr:            true,
+			subnetwork:         "subnetwork-id-1",
 		},
 	}
 
@@ -152,7 +165,7 @@ func TestTerminateVPCs(t *testing.T) {
 				subnetworksAPI:     tc.subnetworksAPI,
 				firewalls:          tc.firewalls,
 				network:            "network-id-1",
-				subnetwork:         "subnetwork-id-1",
+				subnetwork:         tc.subnetwork,
 			}
 
 			if tc.wantErr {

cli/gcp/client/operation.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
 	computepb "google.golang.org/genproto/googleapis/cloud/compute/v1"
@@ -12,6 +13,8 @@ import (
 func (c *Client) waitForOperations(ctx context.Context, ops []Operation) error {
 	for _, op := range ops {
 		switch {
+		case op.Proto() == nil:
+			return errors.New("proto of operation is nil")
 		case op.Proto().Zone != nil:
 			if err := c.waitForZoneOperation(ctx, op); err != nil {
 				return err