This is due to ContextInitializer, which uses the extension (.xml or .groove) to determine whether to parse the file as a groovy script or xml configuration file.
That makes some sense, but I agree this should be (1) documented where logback.configurationFile is documented and (2) an error message should be logged when the file type cannot be determined based on its extension.
That makes some sense, but I agree this should be (1) documented where logback.configurationFile is documented and (2) an error message should be logged when the file type cannot be determined based on its extension.