Add support for tuples in get_attr (boto#3302)

botocore/endpoint_provider.py

@@ -42,7 +42,7 @@
 logger = logging.getLogger(__name__)
 
 TEMPLATE_STRING_RE = re.compile(r"\{[a-zA-Z#]+\}")
-GET_ATTR_RE = re.compile(r"(\w+)\[(\d+)\]")
+GET_ATTR_RE = re.compile(r"(\w*)\[(\d+)\]")
 VALID_HOST_LABEL_RE = re.compile(
     r"^(?!-)[a-zA-Z\d-]{1,63}(?<!-)$",
 )
@@ -169,7 +169,7 @@ def get_attr(self, value, path):
         names indicates the one to the right is nested. The index will always occur at
         the end of the path.
 
-        :type value: dict or list
+        :type value: dict or tuple
         :type path: str
         :rtype: Any
         """
@@ -178,7 +178,8 @@ def get_attr(self, value, path):
             if match is not None:
                 name, index = match.groups()
                 index = int(index)
-                value = value.get(name)
+                if name:
+                    value = value.get(name)
                 if value is None or index >= len(value):
                     return None
                 return value[index]

tests/unit/test_endpoint_provider.py

@@ -510,3 +510,33 @@ def test_aws_is_virtual_hostable_s3_bucket_allow_subdomains(
         rule_lib.aws_is_virtual_hostable_s3_bucket(bucket, True)
         == expected_value
     )
+
+
+@pytest.mark.parametrize(
+    "value, path, expected_value",
+    [
+        ({"foo": ['bar']}, 'baz[0]', None),  # Missing index
+        ({"foo": ['bar']}, 'foo[1]', None),  # Out of range index
+        ({"foo": ['bar']}, 'foo[0]', "bar"),  # Named index
+        (("foo",), '[0]', "foo"),  # Bare index
+        ({"foo": {}}, 'foo.bar[0]', None),  # Missing index from split path
+        (
+            {"foo": {'bar': []}},
+            'foo.bar[0]',
+            None,
+        ),  # Out of range from split path
+        (
+            {"foo": {"bar": "baz"}},
+            'foo.bar',
+            "baz",
+        ),  # Split path with named index
+        (
+            {"foo": {"bar": ["baz"]}},
+            'foo.bar[0]',
+            "baz",
+        ),  # Split path with numeric index
+    ],
+)
+def test_get_attr(rule_lib, value, path, expected_value):
+    result = rule_lib.get_attr(value, path)
+    assert result == expected_value