fix percent escape && add test

mako/lexer.py

@@ -357,10 +357,12 @@ def match_text(self):
             r"""
                 (.*?)         # anything, followed by:
                 (
-                 (?<=\n)(?=[ \t]*(?=%|\#\#)) # an eval or line-based
+                 ((?<=\n)|^)(?=[ \t]*(?=%|\#\#)) # an eval or line-based
                                              # comment preceded by a
                                              # consumed newline and whitespace
                  |
+                 (?<!%)(?=%%+)
+                 |
                  (?=\${)      # an expression
                  |
                  (?=</?[%&])  # a substitution or block or call start or end

test/test_lexer.py

@@ -202,14 +202,35 @@ def test_percent_escape(self):
                 [
                     Text("""\n\n""", (1, 1)),
                     Text("""% some whatever.\n\n""", (3, 2)),
-                    Text("   %% more some whatever\n", (5, 2)),
+                    Text("   ", (5, 2)),
+                    Text("% more some whatever\n", (5, 6)),
                     ControlLine("if", "if foo:", False, (6, 1)),
                     ControlLine("if", "endif", True, (7, 1)),
                     Text("        ", (8, 1)),
                 ],
             ),
         )
 
+    def test_percent_escape2(self):
+        template = """%% do something
+%%% do something
+if <some condition>:
+    %%%% do something
+        """
+        node = Lexer(template).parse()
+        self._compare(
+            node,
+            TemplateNode(
+                {},
+                [
+                    Text("% do something\n", (1, 2)),
+                    Text("%% do something\nif <some condition>:\n", (2, 2)),
+                    Text("   ", (4, 2)),
+                    Text("%%% do something\n        ", (4, 6)),
+                ],
+            ),
+        )
+
     def test_old_multiline_comment(self):
         template = """#*"""
         node = Lexer(template).parse()

test/test_template.py

@@ -1667,3 +1667,20 @@ class FuturesTest(TemplateTest):
     def test_future_import(self):
         t = Template("${ x / y }", future_imports=["division"])
         assert result_lines(t.render(x=12, y=5)) == ["2.4"]
+
+
+class EscapeTest(TemplateTest):
+    def test_percent_escape(self):
+        t = Template(
+            """%% do something
+%%% do something
+if <some condition>:
+    %%%% do something
+"""
+        )
+        assert result_lines(t.render()) == [
+            "% do something",
+            "%% do something",
+            "if <some condition>:",
+            "%%% do something",
+        ]