Fix undeclared variables in nested list comprehension with strict_undefined

Fix undefined variable errors when ``strict_undefined=True`` when using a
nested list comprehension.  Pull request courtesy Sébastien Granjoux.

Fixes: #418
Closes: #419
Pull-request: #419
Pull-request-sha: 0b64e72

Change-Id: I13f6296ffe1f5f0d5f68b7da07ff76bbac7668e0

Author: Sébastien Granjoux

doc/build/unreleased/418.rst

@@ -0,0 +1,7 @@
+.. change::
+    :tags: bug, lexer
+    :tickets: 418
+
+    Fix undefined variable errors when ``strict_undefined=True`` when using a
+    nested list comprehension.  Pull request courtesy Sébastien Granjoux.
+

mako/pyparser.py

@@ -93,6 +93,7 @@ def visit_FunctionDef(self, node):
     def visit_ListComp(self, node):
         if self.in_function:
             for comp in node.generators:
+                self.visit(comp.target)
                 self.visit(comp.iter)
         else:
             self.generic_visit(node)
@@ -102,6 +103,7 @@ def visit_ListComp(self, node):
     def visit_DictComp(self, node):
         if self.in_function:
             for comp in node.generators:
+                self.visit(comp.target)
                 self.visit(comp.iter)
         else:
             self.generic_visit(node)

test/test_template.py

@@ -916,6 +916,19 @@ def foo():
 
         eq_(result_lines(t.render()), ["foo"])
 
+    def test_nested_list_comprehensions_in_function_plus_undeclared_strict(
+        self,
+    ):
+        t = Template(
+            """
+<%foo = lambda b : sum(f for s in b for f in s)%>\
+${ foo(([1,2],[3,4]))}
+""",
+            strict_undefined=True,
+        )
+
+        eq_(result_lines(t.render()), ["10"])
+
 
 class StopRenderingTest(TemplateTest):
     def test_return_in_template(self):