Export service provider format error

Question

During a development of the Export plugin I've run into a problem:
Need to export some files to multiple formats (depends on the original format: JPEG or DNG)
but according to the documentation the settings of export allow only one of the supported formats (JPEG, PSD, TIFF, DNG, ORIGINAL).
Is there some way to come over this limitation? If YES please show me how.
And the second thing: when I set only one format in `allowFileFormats` option ('DNG') regardless of the origin file format I always get JPEG one. However, if I set few output formats in
`allowFileFormats` such as ( TIFF, DNG) as a result I get the correct one (according to my settings). So my question is: is it a bug or a feature?

Answer 1

Well those are the only formats (JPEG, PSD, TIFF, DNG, ORIGINAL), but if you want to do 2 in 1 go, you have to roll your own export using:
local es = LrExportSession { photosToExport=photos, exportSettings=settings }
es.doExportOnCurrentTask()
something like that.
PS - No export filters allowed when rolling ad-hoc exports.
Rob