Improve support for trailing commas in macro signatures, calls & with statements

CHANGES.rst

@@ -5,6 +5,8 @@ Version 3.2.0
 
 Unreleased
 
+- Add support for trailing commas on macro signatures and with statements. :pr:`1712`
+
 
 Version 3.1.2
 -------------

docs/templates.rst

@@ -956,6 +956,8 @@ override a macro in a parent template. The following will output
     {% macro foo() %}CHILD{% endmacro %}
     {% block body %}{{ foo() }}{% endblock %}
 
+.. versionadded:: 3.2.0 Added support for trailing commas in macro signatures
+
 
 .. _call:
 
@@ -1922,6 +1924,9 @@ use the ``set`` tag::
    In older versions of Jinja (before 2.9) it was required to enable this
    feature with an extension.  It's now enabled by default.
 
+.. versionadded:: 3.2.0 Added support for trailing commas in with statements
+
+
 .. _autoescape-overrides:
 
 Autoescape Overrides

src/jinja2/parser.py

@@ -275,6 +275,9 @@ def parse_with(self) -> nodes.With:
         while self.stream.current.type != "block_end":
             if targets:
                 self.stream.expect("comma")
+            # support for trailing comma
+            if self.stream.current.type == "block_end":
+                break
             target = self.parse_assign_target()
             target.set_ctx("param")
             targets.append(target)
@@ -406,6 +409,9 @@ def parse_signature(self, node: _MacroCall) -> None:
         while self.stream.current.type != "rparen":
             if args:
                 self.stream.expect("comma")
+            # support for trailing comma
+            if self.stream.current.type == "rparen":
+                break
             arg = self.parse_assign_target(name_only=True)
             arg.set_ctx("param")
             if self.stream.skip_if("assign"):
@@ -747,6 +753,7 @@ def parse_list(self) -> nodes.List:
         while self.stream.current.type != "rbracket":
             if items:
                 self.stream.expect("comma")
+            # support for trailing comma
             if self.stream.current.type == "rbracket":
                 break
             items.append(self.parse_expression())
@@ -759,6 +766,7 @@ def parse_dict(self) -> nodes.Dict:
         while self.stream.current.type != "rbrace":
             if items:
                 self.stream.expect("comma")
+            # support for trailing comma
             if self.stream.current.type == "rbrace":
                 break
             key = self.parse_expression()

tests/test_core_tags.py

@@ -415,6 +415,30 @@ def test_caller_undefined(self, env_trim):
         )
         assert tmpl.render() == "True"
 
+    def test_trailing_comma_signature(self, env_trim):
+        tmpl = env_trim.from_string(
+            """\
+{% macro m(a, b,) %}{{ a }}|{{ b }}{% endmacro %}
+{{ m(1,2) }}"""
+        )
+        assert tmpl.render() == "1|2"
+
+    def test_trailing_comma_arguments(self, env_trim):
+        tmpl = env_trim.from_string(
+            """\
+{% macro m(a, b) %}{{ a }}|{{ b }}{% endmacro %}
+{{ m(1,2,) }}"""
+        )
+        assert tmpl.render() == "1|2"
+
+    def test_trailing_comma_call(self, env_trim):
+        tmpl = env_trim.from_string(
+            """\
+{% macro test(a) %}{{ a }}|[[{{ caller() }}]]{% endmacro %}\
+{% call test(a=42,) %}data{% endcall %}"""
+        )
+        assert tmpl.render() == "42|[[data]]"
+
     def test_include(self, env_trim):
         env_trim = Environment(
             loader=DictLoader(
@@ -593,3 +617,12 @@ def test_with_argument_scoping(self, env):
         """
         )
         assert tmpl.render(b=3, e=4) == "1|2|3|4|5"
+
+    def test_with_trailing_comma(self, env):
+        tmpl = env.from_string(
+            """\
+        {% with a=42, b=23, -%}
+            {{ a }} = {{ b }}
+        {% endwith -%}"""
+        )
+        assert tmpl.render().strip() == "42 = 23"