Skateboard chokes on kerning?

GregThompson

I've been using Skateboard in design of a two-axes variable font. So far all is well, but now I'm adding kerning to my ufo's and Skateboard is not liking it. I can visualize the fonts in the text window throughout the design space, but trying to create a Preview UFO gets the following error:

Something went wrong. At this time it may not be possible to assign blame and point fingers. So, pardon the traceback posted below, it may be helpful in a report. Thanks!

Traceback (most recent call last):
  File "/Users/gregory/Library/Application Support/RoboFont/plugins/Skateboard.roboFontExt/lib/skateboard.py", line 3992, in export_generateUFOCallback
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/ufoProcessor/__init__.py", line 669, in makeInstance
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/ufoProcessor/__init__.py", line 393, in getKerningMutator
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontMath/mathKerning.py", line 27, in __init__
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontMath/mathKerning.py", line 35, in update
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/kerning.py", line 396, in keys
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/base.py", line 278, in keys
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/base.py", line 287, in _keys
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/kerning.py", line 386, in items
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/base.py", line 295, in items
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/base.py", line 295, in <listcomp>
  File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/normalizers.py", line 131, in normalizeKerningKey
ValueError: Kerning key items must be one character long

frederik

good you found it!
kerning values has to be set very precise.

Did the extension DesignSpaceEditor show this kern error in the report?

good luck!

GregThompson

Found the problem. It was a kerning pair without a Side 1 glyph. And only in one ufo, the first ufo I kerned. I then copied that kerning info into the other three ufo's but the error didn't copy.

GregThompson

@GregThompson More detail on my situation.

There are four ufo sources
Each ufo has identical kerning groups, pairs, and values
859 pairs, 143 groups, 399 glyphs in each ufo
Robofont 3.4, Skateboard 1.6.1, MetricsMachine 1.1.0
otf and variable fonts generate with no errors

SOLVED Skateboard chokes on kerning?