From 22bfc305eef84115ff3e893a0438256394442e08 Mon Sep 17 00:00:00 2001
From: Khaled Hosny <khaledhosny@eglug.org>
Date: Wed, 29 Jan 2020 22:34:25 +0200
Subject: [PATCH] [feaLib] fix mixed single/multiple substitutions

If the single substitution involved a glyph class, we were incorrectly
using only the first glyph in the class.

Broken since ec6ff821f0e72022d7aec8794b6bb589d8f81808, apparently no one
else uses this feature!
---
 Lib/fontTools/feaLib/parser.py | 19 ++++++++++++++-----
 Tests/feaLib/parser_test.py    | 10 ++++++++++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/Lib/fontTools/feaLib/parser.py b/Lib/fontTools/feaLib/parser.py
index d8670d6bd..54f9edac0 100644
--- a/Lib/fontTools/feaLib/parser.py
+++ b/Lib/fontTools/feaLib/parser.py
@@ -1452,12 +1452,21 @@ class Parser(object):
 
         # Upgrade all single substitutions to multiple substitutions.
         if has_single and has_multiple:
-            for i, s in enumerate(statements):
+            statements = []
+            for s in block.statements:
                 if isinstance(s, self.ast.SingleSubstStatement):
-                    statements[i] = self.ast.MultipleSubstStatement(
-                        s.prefix, s.glyphs[0].glyphSet()[0], s.suffix,
-                        [r.glyphSet()[0] for r in s.replacements],
-                        s.forceChain, location=s.location)
+                    glyphs = s.glyphs[0].glyphSet()
+                    replacements = s.replacements[0].glyphSet()
+                    if len(replacements) == 1:
+                        replacements *= len(glyphs)
+                    for i, glyph in enumerate(glyphs):
+                        statements.append(
+                            self.ast.MultipleSubstStatement(
+                                s.prefix, glyph, s.suffix, [replacements[i]],
+                                s.forceChain, location=s.location))
+                else:
+                    statements.append(s)
+            block.statements = statements
 
     def is_cur_keyword_(self, k):
         if self.cur_token_type_ is Lexer.NAME:
diff --git a/Tests/feaLib/parser_test.py b/Tests/feaLib/parser_test.py
index a5b9f69c8..e11a68789 100644
--- a/Tests/feaLib/parser_test.py
+++ b/Tests/feaLib/parser_test.py
@@ -1396,12 +1396,22 @@ class ParserTest(unittest.TestCase):
                          "  sub f_f   by f f;"
                          "  sub f     by f;"
                          "  sub f_f_i by f f i;"
+                         "  sub [a a.sc] by a;"
+                         "  sub [a a.sc] by [b b.sc];"
                          "} Look;")
         statements = doc.statements[0].statements
         for sub in statements:
             self.assertIsInstance(sub, ast.MultipleSubstStatement)
         self.assertEqual(statements[1].glyph, "f")
         self.assertEqual(statements[1].replacement, ["f"])
+        self.assertEqual(statements[3].glyph, "a")
+        self.assertEqual(statements[3].replacement, ["a"])
+        self.assertEqual(statements[4].glyph, "a.sc")
+        self.assertEqual(statements[4].replacement, ["a"])
+        self.assertEqual(statements[5].glyph, "a")
+        self.assertEqual(statements[5].replacement, ["b"])
+        self.assertEqual(statements[6].glyph, "a.sc")
+        self.assertEqual(statements[6].replacement, ["b.sc"])
 
     def test_substitute_from(self):  # GSUB LookupType 3
         doc = self.parse("feature test {"