version 4.35.0 breaks our tests in gftools

v4.35.0 breaks two of our builder checks, https://github.com/googlefonts/gftools/runs/7839959593?check_suite_focus=true#step:5:186. Here’s the traceback

ERROR:root:In 'Lora.glyphs' -> 'master_ufo/Lora.designspace': Generating fonts from Designspace failed: <fontTools.feaLib.ast.GlyphName object at 0x108267610>
Traceback (most recent call last):
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/fontmake/font_project.py", line 1065, in run_from_designspace
    self._run_from_designspace_interpolatable(
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/fontmake/font_project.py", line 1157, in _run_from_designspace_interpolatable
    self.build_variable_fonts(
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/fontmake/font_project.py", line 384, in build_variable_fonts
    fonts = ufo2ft.compileVariableTTFs(
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/__init__.py", line 596, in compileVariableTTFs
    vfNameToBaseUfo = _compileNeededSources(
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/__init__.py", line 785, in _compileNeededSources
    ttfDesignSpace = compileInterpolatableFunc(
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/__init__.py", line 384, in compileInterpolatableTTFsFromDS
    for source, ttf in zip(result.sources, ttfs):
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/__init__.py", line 318, in compileInterpolatableTTFs
    compileFeatures(ufo, ttf, glyphSet=glyphSet, **kwargs)
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/__init__.py", line 507, in compileFeatures
    otFont = featureCompiler.compile()
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/featureCompiler.py", line 127, in compile
    self.setupFeatures()
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/featureCompiler.py", line 265, in setupFeatures
    writer.write(self.ufo, featureFile, compiler=self)
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/featureWriters/baseFeatureWriter.py", line 131, in write
    return self._write()
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/featureWriters/cursFeatureWriter.py", line 119, in _write
    feature = self._makeCursiveFeature()
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/featureWriters/cursFeatureWriter.py", line 26, in _makeCursiveFeature
    gsub = self.compileGSUB()
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/featureWriters/baseFeatureWriter.py", line 321, in compileGSUB
    gsub = compileGSUB(self.context.feaFile, glyphOrder)
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/ufo2ft/util.py", line 230, in compileGSUB
    addOpenTypeFeatures(font, featureFile, tables={"GSUB"})
  File "/Users/marcfoley/Type/fonttools/Lib/fontTools/feaLib/builder.py", line 64, in addOpenTypeFeatures
    builder.build(tables=tables, debug=debug)
  File "/Users/marcfoley/Type/fonttools/Lib/fontTools/feaLib/builder.py", line 227, in build
    gdef = self.buildGDEF()  # build unconditionally so we can warn below
  File "/Users/marcfoley/Type/fonttools/Lib/fontTools/feaLib/builder.py", line 763, in buildGDEF
    gdef.MarkGlyphSetsDef = self.buildGDEFMarkGlyphSetsDef_()
  File "/Users/marcfoley/Type/fonttools/Lib/fontTools/feaLib/builder.py", line 822, in buildGDEFMarkGlyphSetsDef_
    return otl.buildMarkGlyphSetsDef(sets, self.glyphMap)
  File "/Users/marcfoley/Type/fonttools/Lib/fontTools/otlLib/builder.py", line 2618, in buildMarkGlyphSetsDef
    self.Coverage = [buildCoverage(m, glyphMap) for m in markSets]
  File "/Users/marcfoley/Type/fonttools/Lib/fontTools/otlLib/builder.py", line 2618, in <listcomp>
    self.Coverage = [buildCoverage(m, glyphMap) for m in markSets]
  File "/Users/marcfoley/Type/fonttools/Lib/fontTools/otlLib/builder.py", line 58, in buildCoverage
    self.glyphs = sorted(set(glyphs), key=glyphMap.__getitem__)
KeyError: <fontTools.feaLib.ast.GlyphName object at 0x108267610>

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/fontmake/__main__.py", line 620, in main
    project.run_from_glyphs(inputs.glyphs_path, **args)
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/fontmake/font_project.py", line 787, in run_from_glyphs
    self.run_from_designspace(designspace_path, **kwargs)
  File "/Users/marcfoley/Type/fonttools/venv/lib/python3.10/site-packages/fontmake/font_project.py", line 1080, in run_from_designspace
    raise FontmakeError(
fontmake.errors.FontmakeError: In 'Lora.glyphs' -> 'master_ufo/Lora.designspace': Generating fonts from Designspace failed: <fontTools.feaLib.ast.GlyphName object at 0x108267610>

I’ve narrowed it down to commit https://github.com/fonttools/fonttools/commit/e4c5c842f1638c2debd801ebc35cafd8a0e346fe.

To replicate, download the attached file and do: fontmake -g Lora.glyphs -o variable

Lora.glyphs.zip

[simoncozens]

Turns out the fix is obvious, once you have a type checker. 😃

diff --git a/Lib/fontTools/feaLib/parser.py b/Lib/fontTools/feaLib/parser.py
index cd59e48fe..eb1e5fd2f 100644
--- a/Lib/fontTools/feaLib/parser.py
+++ b/Lib/fontTools/feaLib/parser.py
@@ -936,7 +936,7 @@ class Parser(object):
                     raise FeatureLibError("Empty class in replacement", location)
             return self.ast.MultipleSubstStatement(
                 old_prefix,
-                tuple(old[0].glyphSet())[0],
+                self.ast.GlyphName(tuple(old[0].glyphSet())[0]),
                 old_suffix,
                 tuple([list(n.glyphSet())[0] for n in new]),
                 forceChain=hasMarks,

I’ll include this in the upcoming Big Type-Checking PR.

[simoncozens]

This is a typing problem in ast.py/parser.py. I’ve tracked it down but the fix is less obvious.