js: Add JetStreamAPIError with more api response details

Signed-off-by: Waldemar Quevedo <wally@nats.io>

jsm.go

@@ -161,6 +161,37 @@ type APIError struct {
 	Description string `json:"description,omitempty"`
 }
 
+// JetStreamAPIError is an error result from making a request to the
+// JetStream API.
+type JetStreamAPIError interface {
+	Code() int
+	ErrorCode() int
+	Description() string
+	Error() string
+}
+
+type jsAPIError struct {
+	code        int
+	errorCode   int
+	description string
+}
+
+func (err *jsAPIError) Code() int {
+	return err.code
+}
+
+func (err *jsAPIError) ErrorCode() int {
+	return err.errorCode
+}
+
+func (err *jsAPIError) Description() string {
+	return err.description
+}
+
+func (err *jsAPIError) Error() string {
+	return "nats: jetstream not enabled"
+}
+
 // apiResponse is a standard response from the JetStream JSON API
 type apiResponse struct {
 	Type  string    `json:"type"`
@@ -245,10 +276,15 @@ func (js *js) AccountInfo(opts ...JSOpt) (*AccountInfo, error) {
 	}
 	if info.Error != nil {
 		var err error
-		if strings.Contains(info.Error.Description, "not enabled for") {
+		// Check based on error code instead of description match.
+		if info.Error.ErrorCode == ErrJetStreamNotEnabled.ErrorCode() {
 			err = ErrJetStreamNotEnabled
 		} else {
-			err = errors.New(info.Error.Description)
+			err = &jsAPIError{
+				code:        info.Error.Code,
+				errorCode:   info.Error.ErrorCode,
+				description: info.Error.Description,
+			}
 		}
 		return nil, err
 	}

nats.go

@@ -139,7 +139,6 @@ var (
 	ErrNoResponders                 = errors.New("nats: no responders available for request")
 	ErrNoContextOrTimeout           = errors.New("nats: no context or timeout given")
 	ErrPullModeNotAllowed           = errors.New("nats: pull based not supported")
-	ErrJetStreamNotEnabled          = errors.New("nats: jetstream not enabled")
 	ErrJetStreamBadPre              = errors.New("nats: jetstream api prefix not valid")
 	ErrNoStreamResponse             = errors.New("nats: no response from stream")
 	ErrNotJSMessage                 = errors.New("nats: not a jetstream message")
@@ -172,6 +171,11 @@ var (
 	ErrConnectionNotTLS             = errors.New("nats: connection is not tls")
 )
 
+var (
+	// ErrJetStreamNotEnabled is an error returned when JetStream is not enabled for an account.
+	ErrJetStreamNotEnabled JetStreamAPIError = &jsAPIError{errorCode: 10039}
+)
+
 func init() {
 	rand.Seed(time.Now().UnixNano())
 }

test/js_test.go

@@ -87,9 +87,18 @@ func TestJetStreamNotAccountEnabled(t *testing.T) {
 	nc, js := jsClient(t, s)
 	defer nc.Close()
 
-	if _, err := js.AccountInfo(); err != nats.ErrJetStreamNotEnabled {
+	_, err := js.AccountInfo()
+	if err != nats.ErrJetStreamNotEnabled {
 		t.Fatalf("Did not get the proper error, got %v", err)
 	}
+	jserr, ok := err.(nats.JetStreamAPIError)
+	if !ok {
+		t.Fatal("Expected a JetStreamAPIError")
+	}
+	expected := 10039
+	if jserr.ErrorCode() != expected {
+		t.Fatalf("Expected: %v, got: %v", expected, jserr.ErrorCode())
+	}
 }
 
 func TestJetStreamPublish(t *testing.T) {