Creating a proxy writer with the "filtered" flag set is not currently possible via the API and the only ones that are created are built-in ones. Since all built-in ones are using the asynchronous path anyway the absence of a synchronous path is not actually a bug, but the undocumented deviation of the pattern is.
Not deviating from the patter is the better option here, especially because it is constitutes a significant fraction of performing content filtering at the writer and so its use is likely to be extended.
Creating a proxy writer with the "filtered" flag set is not currently possible via the API and the only ones that are created are built-in ones. Since all built-in ones are using the asynchronous path anyway the absence of a synchronous path is not actually a bug, but the undocumented deviation of the pattern is.
Not deviating from the patter is the better option here, especially because it is constitutes a significant fraction of performing content filtering at the writer and so its use is likely to be extended.
Fixes #2018