improve error message when interpolations goes wrong.

fixing #93

Author: typemytype

source/lib/batchCompileTools.py

@@ -3,6 +3,10 @@
 import batchSettings
 
 
+class BatchException(Exception):
+    pass
+
+
 def generateDesktopFonts(ufoPathsOrObjects, destinationRoot, format="ttf", decompose=True, removeOverlap=True, autohint=False, releaseMode=True, suffix=""):
     if not isinstance(ufoPathsOrObjects, list):
         ufoPathsOrObjects = [ufoPathsOrObjects]

source/lib/batchGenerators/variableFontsGenerator/__init__.py

@@ -17,6 +17,7 @@
 from ufo2fdk.kernFeatureWriter import side1Prefix, side2Prefix
 
 from batchGenerators.batchTools import postProcessCollector, WOFF2Builder, buildTree, removeTree, BatchEditorOperator, Report
+from batchCompileTools import BatchException
 
 
 class GenerateVariableFont:
@@ -153,6 +154,9 @@ def makeSourceGlyphsCompatible(self):
                     clip=False
                 )
                 self.report.write(f"Adding missing glyph '{glyphName}' in the default source '{defaultSource.info.familyName} {defaultSource.info.styleName}'")
+                if result is None:
+                    # no result
+                    raise BatchException(f"Unable to generate instance for missing glyph '{glyphName}' in the default source. '{defaultSource.info.familyName} {defaultSource.info.styleName}'")
                 # add the glyph to the default source
                 glyph = defaultSource.newGlyph(glyphName)
                 result.extractGlyph(glyph, onlyGeometry=True)
@@ -177,6 +181,9 @@ def makeSourceGlyphsCompatible(self):
                     clip=False
                 )
                 self.report.write(f"Adding missing glyph '{glyphName}' in the source '{sourceFont.info.familyName} {sourceFont.info.styleName}'")
+                if result is None:
+                    # no result
+                    raise BatchException(f"Unable to generate instance for missing glyph '{glyphName}' in the source '{sourceFont.info.familyName} {sourceFont.info.styleName}'")
                 # add the glyph to the source
                 glyph = sourceFont.newGlyph(glyphName)
                 result.extractGlyph(glyph, onlyGeometry=True)