Wrap ErrKeyExists on kv.Create WrongLastSequence error

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

jserrors.go

@@ -124,7 +124,7 @@ const (
 
 	JSErrCodeBadRequest ErrorCode = 10003
 
-	JSErrStreamWrongLastSequence ErrorCode = 10071
+	JSErrCodeStreamWrongLastSequence ErrorCode = 10071
 )
 
 // APIError is included in all API responses if there was an error.

kv.go

@@ -299,12 +299,8 @@ var (
 	ErrNoKeysFound            = errors.New("nats: no keys found")
 )
 
-// KeyValueError is an error result for KeyValue operations which internally
-// are JetStreamError as well so this is just an alias.
-type KeyValueError = JetStreamError
-
 var (
-	ErrKeyExists KeyValueError = &jsError{apiErr: &APIError{ErrorCode: JSErrStreamWrongLastSequence, Description: "key exists", Code: 400}}
+	ErrKeyExists JetStreamError = &jsError{apiErr: &APIError{ErrorCode: JSErrCodeStreamWrongLastSequence, Code: 400}, message: "key exists"}
 )
 
 const (
@@ -637,6 +633,13 @@ func (kv *kvs) Create(key string, value []byte) (revision uint64, err error) {
 		return kv.Update(key, value, e.Revision())
 	}
 
+	// Check if the expected last subject sequence is not zero which implies
+	// the key already exists.
+	var aerr *APIError
+	if errors.Is(err, ErrKeyExists) && errors.As(err, &aerr) {
+		return 0, fmt.Errorf("%w: %s", ErrKeyExists, aerr.Description)
+	}
+
 	return 0, err
 }
 

kv_test.go

@@ -223,7 +223,7 @@ func TestKeyValueCreate(t *testing.T) {
 	}
 
 	_, err = kv.Create("key", []byte("1"))
-	expected := "nats: wrong last sequence: 1"
+	expected := "nats: key exists: wrong last sequence: 1"
 	if err.Error() != expected {
 		t.Fatalf("Expected %q, got: %v", expected, err)
 	}
@@ -240,7 +240,7 @@ func TestKeyValueCreate(t *testing.T) {
 	if aerr.Code != ErrKeyExists.APIError().Code {
 		t.Fatalf("Unexpected error code, got: %v", aerr.Code)
 	}
-	var kerr KeyValueError
+	var kerr JetStreamError
 	if !errors.As(err, &kerr) {
 		t.Fatalf("Expected KeyValueError, got: %v", err)
 	}