js: make an APIError implement the interface

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

jsm.go

@@ -166,6 +166,11 @@ func (e *APIError) Error() string {
 	return fmt.Sprintf("nats: API error %d: %s", e.ErrorCode, e.Description)
 }
 
+// APIError implements the JetStreamError interface.
+func (e *APIError) APIError() *APIError {
+	return e
+}
+
 // Is matches against an APIError.
 func (e *APIError) Is(err error) bool {
 	// Extract internal APIError to match against.
@@ -303,14 +308,11 @@ func (js *js) AccountInfo(opts ...JSOpt) (*AccountInfo, error) {
 		return nil, err
 	}
 	if info.Error != nil {
-		var err error
+		var err JetStreamError = info.Error
+
 		// Internally checks based on error code instead of description match.
 		if errors.Is(info.Error, ErrJetStreamNotEnabledForAccount) {
 			err = ErrJetStreamNotEnabledForAccount
-		} else {
-			err = &jsError{
-				apiErr: info.Error,
-			}
 		}
 		return nil, err
 	}

test/js_test.go

@@ -134,6 +134,9 @@ func TestJetStreamNotAccountEnabled(t *testing.T) {
 		t.Fatalf("Expected: %v, got: %v", expectedMessage, apierr.Error())
 	}
 
+	// an APIError also implements the JetStreamError interface.
+	var _ nats.JetStreamError = &nats.APIError{}
+
 	// matching arbitrary custom error via errors.Is(...)
 	customErr := &nats.APIError{ErrorCode: expected}
 	if ok := errors.Is(customErr, nats.ErrJetStreamNotEnabledForAccount); !ok {
@@ -143,6 +146,10 @@ func TestJetStreamNotAccountEnabled(t *testing.T) {
 	if ok := errors.Is(customErr, nats.ErrJetStreamNotEnabledForAccount); ok {
 		t.Fatal("Expected to not match ErrJetStreamNotEnabled")
 	}
+	var cerr nats.JetStreamError
+	if ok := errors.As(customErr, &cerr); !ok {
+		t.Fatal("Expected custom error to be a JetStreamError")
+	}
 
 	// matching to concrete type via errors.As(...)
 	var aerr *nats.APIError