[Question] LOGBACK-1673 and conditional appender configuration

[edudar]

In LOGBACK-1673 it was mentioned that

One notable change is that, <if>/<then> elements cannot be embedded within "second phase" elements such as <appender>/<root>/<logger>. The<if>/<then> elements must be located under <configuration> or other "first phase elements", i.e. all elements other than <appender>/<root>/<logger>.

In my case, I have a conditional configuration for an appender. There's a chunk of attributes that I don't include when some property is not set. For example,

<appender name="..." class="...">
    <log>...</log>
    <flushLevel>...</flushLevel>
    <if condition='...'>
        <then>
            <partialSuccess>true</partialSuccess>
            <logbackBatchingSettings>
                <elementCountThreshold>...</elementCountThreshold>
                ...
            </logbackBatchingSettings>
        </then>
    </if>
</appender>

With the sanity check in place, I don't see any way to configure this properly without duplicating appenders: one with these settings and the same one but without, then introducing a logic to include only one of them later. That looks like a lot of duplication and exposing properties/logic that I'd rather have in the <include>d xml.

What's the best way to express a conditional configuration for an appender in 1.3/1.4?