instancer: always keep FeatureVariationRecords with unknown condition format

there was a logic issue in the function that checks whether a FeatureVariationRecord
has a unique set of condition (was returning False instead of True for unsupported condition).
It's safer to always keep such records with unknown condition formats as new formats
may be added in the future. A warning is already issued in these cases.

Lib/fontTools/varLib/instancer.py

@@ -419,8 +419,8 @@ def _featureVariationRecordIsUnique(rec, seen):
     conditionSet = []
     for cond in rec.ConditionSet.ConditionTable:
         if cond.Format != 1:
-            # can't tell whether this is duplicate, assume not seen
-            return False
+            # can't tell whether this is duplicate, assume is unique
+            return True
         conditionSet.append(
             (cond.AxisIndex, cond.FilterRangeMinValue, cond.FilterRangeMaxValue)
         )
@@ -474,6 +474,7 @@ def _instantiateFeatureVariations(table, fvarAxes, location):
                 )
                 applies = False
                 newConditions.append(condition)
+                break
 
         if retainRecord and newConditions:
             record.ConditionSet.ConditionTable = newConditions

Tests/varLib/instancer_test.py

@@ -1285,9 +1285,8 @@ class InstantiateFeatureVariationsTest(object):
     def test_unsupported_condition_format(self, varfont3):
         gsub = varfont3["GSUB"].table
         featureVariations = gsub.FeatureVariations
-        cd = featureVariations.FeatureVariationRecord[0].ConditionSet.ConditionTable[0]
-        assert cd.Format == 1
-        cd.Format = 2
+        rec1 = featureVariations.FeatureVariationRecord[0]
+        rec1.ConditionSet.ConditionTable[0].Format = 2
 
         with CapturingLogHandler("fontTools.varLib.instancer", "WARNING") as captor:
             instancer.instantiateFeatureVariations(varfont3, {"wght": 0})
@@ -1296,3 +1295,6 @@ class InstantiateFeatureVariationsTest(object):
             r"Condition table 0 of FeatureVariationRecord 0 "
             r"has unsupported format \(2\); ignored"
         )
+
+        # check that record with unsupported condition format is kept
+        assert featureVariations.FeatureVariationRecord[0] is rec1