Fix pow and unary operators order

CHANGES.rst

@@ -1,5 +1,10 @@
 .. currentmodule:: jinja2
 
+Unreleased
+
+- Breaking change. The evaluation order of an exponent expression changed. Now it is more consistent with how it's going in pure python. :issue:`1720` :issue:`1722`
+
+
 Version 3.1.2
 -------------
 

docs/templates.rst

@@ -1369,7 +1369,10 @@ but exists for completeness' sake.  The following operators are supported:
 
 ``**``
     Raise the left operand to the power of the right operand.
-    ``{{ 2**3 }}`` would return ``8``.
+    ``{{ 2**3 }}`` would return ``8``
+
+    .. versionchanged:: 3.2
+        From 3.2, this operator has the same evaluation order as in Python. ``{{ 2 ** 3 ** 2 }}`` will be evaluated as ``2 ** (3 ** 2)``.
 
     Unlike Python, chained pow is evaluated left to right.
     ``{{ 3**3**3 }}`` is evaluated as ``(3**3)**3`` in Jinja, but would

src/jinja2/compiler.py

@@ -68,8 +68,9 @@ def visitor(self: "CodeGenerator", node: nodes.BinExpr, frame: Frame) -> None:
             self.write(", ")
             self.visit(node.right, frame)
         else:
-            self.write("(")
+            self.write("((")
             self.visit(node.left, frame)
+            self.write(")")
             self.write(f" {op} ")
             self.visit(node.right, frame)
 

src/jinja2/parser.py

@@ -604,7 +604,7 @@ def parse_concat(self) -> nodes.Expr:
 
     def parse_math2(self) -> nodes.Expr:
         lineno = self.stream.current.lineno
-        left = self.parse_pow()
+        left = self.parse_unary()
         while self.stream.current.type in ("mul", "div", "floordiv", "mod"):
             cls = _math_nodes[self.stream.current.type]
             next(self.stream)
@@ -615,7 +615,7 @@ def parse_math2(self) -> nodes.Expr:
 
     def parse_pow(self) -> nodes.Expr:
         lineno = self.stream.current.lineno
-        left = self.parse_unary()
+        left = self.parse_primary()
         while self.stream.current.type == "pow":
             next(self.stream)
             right = self.parse_unary()
@@ -635,7 +635,7 @@ def parse_unary(self, with_filter: bool = True) -> nodes.Expr:
             next(self.stream)
             node = nodes.Pos(self.parse_unary(False), lineno=lineno)
         else:
-            node = self.parse_primary()
+            node = self.parse_pow()
         node = self.parse_postfix(node)
         if with_filter:
             node = self.parse_filter_expr(node)

tests/test_lexnparse.py

@@ -575,6 +575,26 @@ def test_parse_unary(self, env):
         tmpl = env.from_string('{{ -foo["bar"]|abs }}')
         assert tmpl.render(foo={"bar": 42}) == "42"
 
+    def test_negative_pow(self, env):
+        tmpl = env.from_string("{{ - 1 ** 2 }}")
+        assert tmpl.render() == "-1"
+
+    def test_pow_associative_from_left_to_right(self, env):
+        tmpl = env.from_string("{{ 2 ** 3 ** 2 }}")
+        assert tmpl.render() == "512"
+
+    def test_pow_negative_base(self, env):
+        tmpl = env.from_string("{{ (- 1) ** 2 }}")
+        assert tmpl.render() == "1"
+
+    def test_pow_negative_base_variable_exponent(self, env):
+        tmpl = env.from_string("{{ (- 1) ** x }}", {"x": 2})
+        assert tmpl.render() == "1"
+
+    def test_negative_pow_variable_exponent(self, env):
+        tmpl = env.from_string("{{ - 1 ** x }}", {"x": 2})
+        assert tmpl.render() == "-1"
+
 
 class TestLstripBlocks:
     def test_lstrip(self, env):