[makeinstancesufo] fail better when source files are missing

[frankrolf]

File this under “unexpected problems found during FDK workshop”:

When one of the masters is missing on disk, makeinstancesufo will fail like this:

Masters$ makeinstancesufo -acnv -d Exercise3.designspace 
INFO:afdko.makeinstancesufo:Reading design space file 'Exercise3.designspace' ...
INFO:afdko.makeinstancesufo:Adding Exercise 3 Regular to build list.
INFO:afdko.makeinstancesufo:Adding Exercise 3 Bold to build list.
INFO:afdko.makeinstancesufo:Adding Exercise 3 SemiBold to build list.
INFO:afdko.makeinstancesufo:Building 3 instances...
ERROR:afdko.makeinstancesufo:ufoProcessor error
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/ufoProcessor/__init__.py", line 117, in build
    r = document.generateUFO(processRules=processRules)
  File "/usr/local/lib/python3.7/site-packages/ufoProcessor/__init__.py", line 299, in generateUFO
    font = self.makeInstance(instanceDescriptor, processRules, glyphNames=glyphNames, pairs=pairs, bend=bend)
  File "/usr/local/lib/python3.7/site-packages/ufoProcessor/__init__.py", line 625, in makeInstance
    kerningMutator = self.getKerningMutator()
  File "/usr/local/lib/python3.7/site-packages/ufoProcessor/__init__.py", line 403, in getKerningMutator
    bias, self._kerningMutator = self.getVariationModel(kerningItems, axes=self.serializedAxes, bias=self.defaultLoc)
TypeError: cannot unpack non-iterable NoneType object
INFO:afdko.makeinstancesufo:Built 3 instances.
Traceback (most recent call last):
  File "/usr/local/bin/makeinstancesufo", line 10, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.7/site-packages/afdko/makeinstancesufo.py", line 388, in main
    run(opts)
  File "/usr/local/lib/python3.7/site-packages/afdko/makeinstancesufo.py", line 243, in run
    postProcessInstance(instancePath, options)
  File "/usr/local/lib/python3.7/site-packages/afdko/makeinstancesufo.py", line 210, in postProcessInstance
    dFont = Font(fontPath)
  File "/usr/local/lib/python3.7/site-packages/defcon/objects/font.py", line 148, in __init__
    reader = UFOReader(self._path, validate=self.ufoLibReadValidate)
  File "/usr/local/lib/python3.7/site-packages/fontTools/ufoLib/__init__.py", line 209, in __init__
    structure = _sniffFileStructure(path)
  File "/usr/local/lib/python3.7/site-packages/fontTools/ufoLib/__init__.py", line 1605, in _sniffFileStructure
    raise UFOLibError("No such file or directory: '%s'" % ufo_path)
fontTools.ufoLib.errors.UFOLibError: No such file or directory: '../Instances/Regular/font.ufo'

Perhaps it should fail earlier and clearer, during a global check to see if all source UFOs exist?

[miguelsousa]

Fixed via #821