From ccc2dbb043418cc0575552938a97d11da12f19d9 Mon Sep 17 00:00:00 2001
From: Jannik Zschiesche <jz@becklyn.com>
Date: Mon, 6 Jul 2020 10:34:46 +0200
Subject: [PATCH] Allow trailing commas in macros + functions + filters

---
 CHANGELOG                                     |  2 +-
 src/ExpressionParser.php                      |  5 ++++
 tests/Fixtures/filters/trailing_commas.test   |  8 ++++++
 tests/Fixtures/functions/trailing_commas.test |  8 ++++++
 tests/Fixtures/macros/trailing_commas.test    | 25 +++++++++++++++++++
 5 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 tests/Fixtures/filters/trailing_commas.test
 create mode 100644 tests/Fixtures/functions/trailing_commas.test
 create mode 100644 tests/Fixtures/macros/trailing_commas.test

diff --git a/CHANGELOG b/CHANGELOG
index 41022f515..c0ebddbce 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,6 @@
 # 1.43.1 (2020-XX-XX)
 
- * n/a
+ * Allow trailing commas in argument lists (in calls as well as definitions)
 
 # 1.43.0 (2020-07-05)
 
diff --git a/src/ExpressionParser.php b/src/ExpressionParser.php
index 8bddaf577..1acd48a53 100644
--- a/src/ExpressionParser.php
+++ b/src/ExpressionParser.php
@@ -598,6 +598,11 @@ class ExpressionParser
         while (!$stream->test(Token::PUNCTUATION_TYPE, ')')) {
             if (!empty($args)) {
                 $stream->expect(Token::PUNCTUATION_TYPE, ',', 'Arguments must be separated by a comma');
+
+                // if the comma above was a trailing comma, early exit the argument parse loop
+                if ($stream->test(/* Token::PUNCTUATION_TYPE */ 9, ')')) {
+                    break;
+                }
             }
 
             if ($definition) {
diff --git a/tests/Fixtures/filters/trailing_commas.test b/tests/Fixtures/filters/trailing_commas.test
new file mode 100644
index 000000000..25f1584ff
--- /dev/null
+++ b/tests/Fixtures/filters/trailing_commas.test
@@ -0,0 +1,8 @@
+--TEST--
+filters allow trailing commas in their argument list
+--TEMPLATE--
+{{ 42.55|round(1, 'floor',) }}
+--DATA--
+return []
+--EXPECT--
+42.5
diff --git a/tests/Fixtures/functions/trailing_commas.test b/tests/Fixtures/functions/trailing_commas.test
new file mode 100644
index 000000000..64bf4caf1
--- /dev/null
+++ b/tests/Fixtures/functions/trailing_commas.test
@@ -0,0 +1,8 @@
+--TEST--
+functions allow trailing commas in their argument list
+--TEMPLATE--
+{{ max(1, 2, 3,) }}
+--DATA--
+return []
+--EXPECT--
+3
diff --git a/tests/Fixtures/macros/trailing_commas.test b/tests/Fixtures/macros/trailing_commas.test
new file mode 100644
index 000000000..600247a82
--- /dev/null
+++ b/tests/Fixtures/macros/trailing_commas.test
@@ -0,0 +1,25 @@
+--TEST--
+macros allow trailing commas in their argument and parameter list
+--TEMPLATE--
+{% import _self as test %}
+
+{% macro test(a, b,) -%}
+    {{ a|default('a') }}<br />
+    {{- b|default('b') }}<br />
+{%- endmacro %}
+{% macro test2(a, b) -%}
+    {{ a|default('a') }}<br />
+    {{- b|default('b') }}<br />
+{%- endmacro %}
+
+{{ test.test(1, 2,) }}
+{{ test.test(3, 4) }}
+{{ test.test2(5, 6,) }}
+{{ test.test2(7, 8) }}
+--DATA--
+return []
+--EXPECT--
+1<br />2<br />
+3<br />4<br />
+5<br />6<br />
+7<br />8<br />