Intermediate changes

5 files changed, 28 insertions, 13 deletions

diff --git a/contrib/python/fonttools/fontTools/__init__.py b/contrib/python/fonttools/fontTools/__init__.py
index 0de5c155e3..f2c62f124b 100644
--- a/contrib/python/fonttools/fontTools/__init__.py
+++ b/contrib/python/fonttools/fontTools/__init__.py
@@ -3,6 +3,6 @@ from fontTools.misc.loggingTools import configLogger
 
 log = logging.getLogger(__name__)
 
-version = __version__ = "4.53.0"
+version = __version__ = "4.53.1"
 
 __all__ = ["version", "log", "configLogger"]
diff --git a/contrib/python/fonttools/fontTools/feaLib/builder.py b/contrib/python/fonttools/fontTools/feaLib/builder.py
index a91381ddc1..bda855e1e9 100644
--- a/contrib/python/fonttools/fontTools/feaLib/builder.py
+++ b/contrib/python/fonttools/fontTools/feaLib/builder.py
@@ -1286,10 +1286,7 @@ class Builder(object):
         self, location, prefix, glyph, suffix, replacements, forceChain=False
     ):
         if prefix or suffix or forceChain:
-            chain = self.get_lookup_(location, ChainContextSubstBuilder)
-            sub = self.get_chained_lookup_(location, MultipleSubstBuilder)
-            sub.mapping[glyph] = replacements
-            chain.rules.append(ChainContextualRule(prefix, [{glyph}], suffix, [sub]))
+            self.add_multi_subst_chained_(location, prefix, glyph, suffix, replacements)
             return
         lookup = self.get_lookup_(location, MultipleSubstBuilder)
         if glyph in lookup.mapping:
@@ -1369,7 +1366,7 @@ class Builder(object):
         # https://github.com/fonttools/fonttools/issues/512
         # https://github.com/fonttools/fonttools/issues/2150
         chain = self.get_lookup_(location, ChainContextSubstBuilder)
-        sub = chain.find_chainable_single_subst(mapping)
+        sub = chain.find_chainable_subst(mapping, SingleSubstBuilder)
         if sub is None:
             sub = self.get_chained_lookup_(location, SingleSubstBuilder)
         sub.mapping.update(mapping)
@@ -1377,6 +1374,19 @@ class Builder(object):
             ChainContextualRule(prefix, [list(mapping.keys())], suffix, [sub])
         )
 
+    def add_multi_subst_chained_(self, location, prefix, glyph, suffix, replacements):
+        if not all(prefix) or not all(suffix):
+            raise FeatureLibError(
+                "Empty glyph class in contextual substitution", location
+            )
+        # https://github.com/fonttools/fonttools/issues/3551
+        chain = self.get_lookup_(location, ChainContextSubstBuilder)
+        sub = chain.find_chainable_subst({glyph: replacements}, MultipleSubstBuilder)
+        if sub is None:
+            sub = self.get_chained_lookup_(location, MultipleSubstBuilder)
+        sub.mapping[glyph] = replacements
+        chain.rules.append(ChainContextualRule(prefix, [{glyph}], suffix, [sub]))
+
     # GSUB 8
     def add_reverse_chain_single_subst(self, location, old_prefix, old_suffix, mapping):
         if not mapping:
diff --git a/contrib/python/fonttools/fontTools/misc/visitor.py b/contrib/python/fonttools/fontTools/misc/visitor.py
index d289895467..6de432ef93 100644
--- a/contrib/python/fonttools/fontTools/misc/visitor.py
+++ b/contrib/python/fonttools/fontTools/misc/visitor.py
@@ -61,9 +61,10 @@ class Visitor(object):
             if _visitors is None:
                 break
 
-            m = celf._visitors.get(typ, None)
-            if m is not None:
-                return m
+            for base in typ.mro():
+                m = celf._visitors.get(base, None)
+                if m is not None:
+                    return m
 
         return _default
 
diff --git a/contrib/python/fonttools/fontTools/otlLib/builder.py b/contrib/python/fonttools/fontTools/otlLib/builder.py
index 70fd87ab57..8fc685683a 100644
--- a/contrib/python/fonttools/fontTools/otlLib/builder.py
+++ b/contrib/python/fonttools/fontTools/otlLib/builder.py
@@ -544,6 +544,10 @@ class ChainContextualBuilder(LookupBuilder):
                 f"{classRuleAttr}Count",
                 getattr(setForThisRule, f"{classRuleAttr}Count") + 1,
             )
+        for i, classSet in enumerate(classSets):
+            if not getattr(classSet, classRuleAttr):
+                # class sets can be null so replace nop sets with None
+                classSets[i] = None
         setattr(st, self.ruleSetAttr_(format=2, chaining=chaining), classSets)
         setattr(
             st, self.ruleSetAttr_(format=2, chaining=chaining) + "Count", len(classSets)
@@ -781,14 +785,14 @@ class ChainContextSubstBuilder(ChainContextualBuilder):
                             )
         return result
 
-    def find_chainable_single_subst(self, mapping):
-        """Helper for add_single_subst_chained_()"""
+    def find_chainable_subst(self, mapping, builder_class):
+        """Helper for add_{single,multi}_subst_chained_()"""
         res = None
         for rule in self.rules[::-1]:
             if rule.is_subtable_break:
                 return res
             for sub in rule.lookups:
-                if isinstance(sub, SingleSubstBuilder) and not any(
+                if isinstance(sub, builder_class) and not any(
                     g in mapping and mapping[g] != sub.mapping[g] for g in sub.mapping
                 ):
                     res = sub
diff --git a/contrib/python/fonttools/fontTools/otlLib/maxContextCalc.py b/contrib/python/fonttools/fontTools/otlLib/maxContextCalc.py
index 03e7561b60..eee8d48f3c 100644
--- a/contrib/python/fonttools/fontTools/otlLib/maxContextCalc.py
+++ b/contrib/python/fonttools/fontTools/otlLib/maxContextCalc.py
@@ -92,5 +92,5 @@ def maxCtxContextualRule(maxCtx, st, chain):
     if not chain:
         return max(maxCtx, st.GlyphCount)
     elif chain == "Reverse":
-        return max(maxCtx, st.GlyphCount + st.LookAheadGlyphCount)
+        return max(maxCtx, 1 + st.LookAheadGlyphCount)
     return max(maxCtx, st.InputGlyphCount + st.LookAheadGlyphCount)