From c3fc2266e199e72f8b0ba892d87fd66ea7f93fc9 Mon Sep 17 00:00:00 2001
From: ornariece <25489980+ornariece@users.noreply.github.com>
Date: Sat, 26 Jun 2021 16:04:57 +0200
Subject: [PATCH 1/2] Fix #696 now providing the correct amount of placeholders

---
 lark/load_grammar.py | 9 ++++-----
 tests/test_parser.py | 9 +++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/lark/load_grammar.py b/lark/load_grammar.py
index dbf4a1f..54c7ca0 100644
--- a/lark/load_grammar.py
+++ b/lark/load_grammar.py
@@ -231,12 +231,11 @@ class EBNF_to_BNF(Transformer_InPlace):
                 return not sym.name.startswith('_')
             if isinstance(sym, Terminal):
                 return keep_all_tokens or not sym.filter_out
-            assert False
+            if isinstance(sym, Symbol):
+                return False
+            assert False, sym
 
-        if any(rule.scan_values(will_not_get_removed)):
-            empty = _EMPTY
-        else:
-            empty = ST('expansion', [])
+        empty = ST('expansion', [_EMPTY] * len(list(rule.scan_values(will_not_get_removed))))
 
         return ST('expansions', [rule, empty])
 
diff --git a/tests/test_parser.py b/tests/test_parser.py
index ff4e064..58b1ef5 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -2293,6 +2293,15 @@ def _make_parser_test(LEXER, PARSER):
             self.assertEqual(p.parse("abba").children, ['a', None, 'b', 'b', 'a', None])
             self.assertEqual(p.parse("cbbbb").children, [None, 'c', 'b', 'b', 'b', 'b', None, None])
 
+            p = _Lark("""!start: ["a" "b" "c"] """, maybe_placeholders=True)
+            self.assertEqual(p.parse("").children, [None, None, None])
+            self.assertEqual(p.parse("abc").children, ['a', 'b', 'c'])
+
+            p = _Lark("""!start: ["a" ["b" "c"]] """, maybe_placeholders=True)
+            self.assertEqual(p.parse("").children, [None, None, None])
+            self.assertEqual(p.parse("a").children, ['a', None, None])
+            self.assertEqual(p.parse("abc").children, ['a', 'b', 'c'])
+
 
         def test_escaped_string(self):
             "Tests common.ESCAPED_STRING"

From c24d6ecff51ed5800ad3d44a69a53841ca8dd4ec Mon Sep 17 00:00:00 2001
From: ornariece <25489980+ornariece@users.noreply.github.com>
Date: Sun, 27 Jun 2021 12:33:05 +0200
Subject: [PATCH 2/2] Fix #696 testing for is _EMPTY

---
 lark/load_grammar.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lark/load_grammar.py b/lark/load_grammar.py
index 54c7ca0..7c3d672 100644
--- a/lark/load_grammar.py
+++ b/lark/load_grammar.py
@@ -231,7 +231,7 @@ class EBNF_to_BNF(Transformer_InPlace):
                 return not sym.name.startswith('_')
             if isinstance(sym, Terminal):
                 return keep_all_tokens or not sym.filter_out
-            if isinstance(sym, Symbol):
+            if sym is _EMPTY:
                 return False
             assert False, sym