From 2a9dcdeb8fefae44de19a94d09bffb44eadd9e13 Mon Sep 17 00:00:00 2001
From: Thomas Hebb <tommyhebb@gmail.com>
Date: Fri, 22 May 2020 23:24:22 -0400
Subject: [PATCH] Allow field access for namedtuple in Python 3

`namedtuple` in Python 3 does not provide a `__dict__` attribute. See
https://bugs.python.org/issue24931 for rationale why. As such, if we
want to render keys in `namedtuple`s, we need to use its [`_asdict`][1]
method.

[1]: https://docs.python.org/3/library/collections.html#collections.somenamedtuple._asdict
---
 chevron/renderer.py | 13 +++++++++----
 test_spec.py        | 13 +++++++++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/chevron/renderer.py b/chevron/renderer.py
index 99415da..dfc2a40 100644
--- a/chevron/renderer.py
+++ b/chevron/renderer.py
@@ -66,11 +66,16 @@ def _get_key(key, scopes):
                     scope = scope[child]
                 except (TypeError, AttributeError):
                     try:
-                        # Try the dictionary (Complex types)
-                        scope = scope.__dict__[child]
+                        # Try namedtuple (which does not have __dict__ in
+                        # Python 3: https://bugs.python.org/issue24931)
+                        scope = scope._asdict()[child]
                     except (TypeError, AttributeError):
-                        # Try as a list
-                        scope = scope[int(child)]
+                        try:
+                            # Try the dictionary (Complex types)
+                            scope = scope.__dict__[child]
+                        except (TypeError, AttributeError):
+                            # Try as a list
+                            scope = scope[int(child)]
 
             # Return an empty string if falsy, with two exceptions
             # 0 should return 0, and False should return False
diff --git a/test_spec.py b/test_spec.py
index 56bdea6..d064ffe 100755
--- a/test_spec.py
+++ b/test_spec.py
@@ -1,6 +1,7 @@
 #!/usr/bin/python
 # -*- coding: utf-8 -*-
 
+import collections
 import unittest
 import os
 import json
@@ -435,6 +436,18 @@ class ExpandedCoverage(unittest.TestCase):
 
         self.assertEqual(result, expected)
 
+    def test_namedtuple_data(self):
+        NT = collections.namedtuple('NT', ['foo', 'bar'])
+        args = {
+            'template': '{{foo}} {{bar}}',
+            'data': NT('hello', 'world')
+        }
+
+        result = chevron.render(**args)
+        expected = 'hello world'
+
+        self.assertEqual(result, expected)
+
 
 # Run unit tests from command line
 if __name__ == "__main__":
-- 
2.47.3