Using fs.memoryfs.MemoryFS for speedups?

[twardoch]

ufoLib2 uses PyFilesystem2 ("fs"). There is fs.memoryfs.MemoryFS — has anyone tried it for potential speedups?

I mean, fontmake, glyphsLib etc. might yield speedups if the DesignSpace+UFO intermediates are written into MemoryFS

See fonttools/ufoLib2#161

[anthrotype]

There is no need to serialise intermediate UFOs to virtual disk, we can just pass them on as ufoLib2.Font objects like we already are doing (they are contained in the designspace source.font attributes). The only reason we are writing them out to disk is because MutatorMath required them to be reopened from filenames on disk. Since MutatorMath is now optional and superseded by fontmake.instantiator we can just not write them out unless the requested output is "-o ufo".