Stupid mistake, 'original' filepath is a blender-flavored one, with
potentially weird things like the '//' relative 'header'... This can
work on linux (also it could have broken in other places too), but on
windows that is fully invalid path and python `os.path` library just
generates empty result here.
Simply using proper valid path instead fixes it...
Nice side-effect of using new __annotations__ thingy to store
dynamically-generated fields in a class: __annotations__ dict is not
ensured to exist for a given class, so we may end up modifying on of the
parents' one!
- Logical use of fields since they define type information.
- Avoids using ordered-dict metaclass.
Properties using regular assignments will print a warning and load,
however the order is undefined.
- check for class/static methods assumed nonzero args.
- subclass references and set-flag items are now sorted.
- use 'order' for Py operator mix-ins,
so operator settings don't show in random order.
Transformed 'OrientationHelper' class into 'orientation_helper_factory' function,
which returns an OrientationHelper customized class with specified default axes.
Also 'fix' T43243, since we can easily add a common better behavior now
when both axis settings are incompatible, by systematically changing
the other axis.
Will update 'main' addons in next commit, contrib ones I'll let to the authors
(old behavior is still possible anyway).
For python operators that used the ExportHelper mix-in class, an empty file field would become '.ext', entering and existing the text field would become '.ext.ext',
Now only add an extension if the filename part of the path is set, so '.ext' will still become '.ext.ext' but having only the extension isn't so likely to happen in the first place now.
This is a different fix then the changes suggested in the report but I'd prefer to keep path functions stupid+predictable.
