feat(BaseService): add Clone() method to clone a BaseService instance

This commit adds the BaseService "Clone()" method that can be
used to make a copy of an existing BaseService instance as part
of cloning a generated service struct instance.

v4/core/base_service.go

@@ -106,6 +106,24 @@ func NewBaseService(options *ServiceOptions) (*BaseService, error) {
 	return &service, nil
 }
 
+// Clone will return a copy of "service" suitable for use by a
+// generated service instance to process requests.
+func (service *BaseService) Clone() *BaseService {
+	if IsNil(service) {
+		return nil
+	}
+
+	// First, copy the service options struct.
+	serviceOptions := *service.Options
+
+	// Next, make a copy the service struct, then use the copy of the service options.
+	// Note, we'll re-use the "Client" instance from the original BaseService instance.
+	clone := *service
+	clone.Options = &serviceOptions
+
+	return &clone
+}
+
 // ConfigureService updates the service with external configuration values.
 func (service *BaseService) ConfigureService(serviceName string) error {
 	// Try to load service properties from external config.

v4/core/base_service_test.go

@@ -33,6 +33,33 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestClone(t *testing.T) {
+	var service *BaseService = nil
+	var err error
+
+	// Verify nil.Clone() == nil
+	assert.Nil(t, service.Clone())
+
+	// Verify a non-nil service is cloned correctly.
+	options := &ServiceOptions{
+		URL:           "https://myservice.ibm.com/api/v1",
+		Authenticator: &NoAuthAuthenticator{},
+	}
+	service, err = NewBaseService(options)
+	assert.Nil(t, err)
+	assert.NotNil(t, service.Options.Authenticator)
+	assert.Equal(t, "https://myservice.ibm.com/api/v1", service.Options.URL)
+
+	clone := service.Clone()
+	assert.NotNil(t, clone)
+	assert.Equal(t, service.Client, clone.Client)
+	assert.Equal(t, service.UserAgent, clone.UserAgent)
+	assert.Equal(t, service.DefaultHeaders, clone.DefaultHeaders)
+	assert.Equal(t, service.Options.URL, clone.Options.URL)
+	assert.Equal(t, service.Options.Authenticator, clone.Options.Authenticator)
+	assert.Equal(t, service.Options.EnableGzipCompression, clone.Options.EnableGzipCompression)
+}
+
 // Test a normal JSON-based response.
 func TestRequestGoodResponseJSON(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -60,6 +87,9 @@ func TestRequestGoodResponseJSON(t *testing.T) {
 	assert.NotNil(t, service.Options.Authenticator)
 	assert.Equal(t, AUTHTYPE_BASIC, service.Options.Authenticator.AuthenticationType())
 
+	// Use a cloned service to verify it works ok.
+	service = service.Clone()
+
 	var foo *Foo
 	detailedResponse, err := service.Request(req, &foo)
 	assert.Nil(t, err)
@@ -101,6 +131,9 @@ func TestRequestGoodResponseJSONStream(t *testing.T) {
 	assert.NotNil(t, service.Options.Authenticator)
 	assert.Equal(t, AUTHTYPE_BASIC, service.Options.Authenticator.AuthenticationType())
 
+	// Use a cloned service to verify it works ok.
+	service = service.Clone()
+
 	detailedResponse, err := service.Request(req, new(io.ReadCloser))
 	assert.Nil(t, err)
 	assert.NotNil(t, detailedResponse)
@@ -144,6 +177,9 @@ func TestRequestGoodResponseJSONExtraFields(t *testing.T) {
 	}
 	service, _ := NewBaseService(options)
 
+	// Use a cloned service to verify it works ok.
+	service = service.Clone()
+
 	var foo *Foo
 	detailedResponse, _ := service.Request(req, &foo)
 	result, ok := detailedResponse.Result.(*Foo)