Axis maps break variable font generation

[nicksherman]

When attempting to generate a variable font from a designSpace file that has axis maps, like so:

<axis tag="wght" name="Weight" minimum="300" maximum="700" default="400">
	<labelname xml:lang="en">Weight</labelname>
	<map input="300" output="340" />
	<map input="500" output="485" />
	<map input="600" output="575" />
</axis>

… the process fails without providing the usual Batch Generated Variable Fonts Report.txt or any readout in the Output window. In the log, I get the following traceback:

>> Traceback (most recent call last):
>>   File "/Users/Nick/Library/Application Support/RoboFont/plugins/Batch.roboFontExt/lib/batchTools.py", line 115, in runTask_
>>   File "/Users/Nick/Library/Application Support/RoboFont/plugins/Batch.roboFontExt/lib/variableFontGenerator/__init__.py", line 84, in run
>>   File "/Users/Nick/Library/Application Support/RoboFont/plugins/Batch.roboFontExt/lib/variableFontGenerator/__init__.py", line 286, in generateVariationFont
>>   File "/Users/Nick/Library/Application Support/RoboFont/plugins/Batch.roboFontExt/lib/variableFontGenerator/__init__.py", line 380, in makeMasterGlyphsCompatible
>> AttributeError: 'NoneType' object has no attribute 'name'

The same designSpace file with the axis maps removed generates a working variable font as expected.

I'm using Batch 1.9.8, run from RoboFont 3.3b (build 1905221146).

Here are some files to test the issue: Test.zip

[LettError]

Related to https://github.com/fonttools/fonttools/issues/1655

[LettError]

Keep in mind that the default value you set for an axis is in userspace coordinates. If you don't have a map, userspace == designspace value. Otherwise you need to make sure the default UFO is on the mapped value for the default. In your example. you have Test-Regular on weight=400, because that's what the axis default value is. But, the map for the weight axis says userspace 300 -> designspace 340 and userspace 500 -> designspace 485. That would put the 400 default around (340+485)*.5 = 412.

I would not trust a the floatinging point numbers to match necessarily, so add that to the map: 300, 340, 400, 412, 500, 485, 600, 575

The resulting space opens and previews in Skateboard. There may be further issues in generating a VF, but at least that issue is solved.

[LettError]

This now works with masters on 340, 412 and 750. Default master on 412.

    <axis tag="wght" name="Weight" minimum="300" <beethe maximum="700" default="400">
      <labelname xml:lang="en">Weight</labelname>
      <map input="300" output="340"/>
      <map input="400" output="412"/>
      <map input="500" output="485"/>
      <map input="600" output="575"/>
      <map input="700" output="750"/>
    </axis>
  </axes>