dont consume ampersands

Fixed long standing bug where the sequence ``<&`` would be misinterpreted
by the lexer.   It's not clear why the ampersand character was part of the
characters being consumed here and it may have been an inadvertent bit of
code from one of Mako's predecessor languages.

Fixes: #412
Change-Id: I41ba50da919a6c8b3557bdd2313aa545b51b2b9b

doc/build/unreleased/412.rst

@@ -0,0 +1,8 @@
+.. change::
+    :tags: bug, lexer
+    :tickets: 412
+
+    Fixed long standing bug where the sequence ``<&`` would be misinterpreted
+    by the lexer.   It's not clear why the ampersand character was part of the
+    characters being consumed here and it may have been an inadvertent bit of
+    code from one of Mako's predecessor languages.

mako/lexer.py

@@ -375,7 +375,7 @@ def match_text(self):
                  |
                  (?=\${)      # an expression
                  |
-                 (?=</?[%&])  # a substitution or block or call start or end
+                 (?=</?%)  # a substitution or block or call start or end
                               # - don't consume
                  |
                  (\\\r?\n)    # an escaped newline  - throw away

test/test_lexer.py

@@ -827,6 +827,17 @@ def test_dict_expression_issue_400_regression(self):
             ),
         )
 
+    def test_ampersand_issue_412(self):
+        template = """
+property = <&node>;
+
+"""
+        nodes = Lexer(template).parse()
+        self._compare(
+            nodes,
+            TemplateNode({}, [Text("\nproperty = <&node>;\n\n", (1, 1))]),
+        )
+
     def _dont_test_dict_expression_issue_400(self):
         """test for issue #400"""
         template = """