From c0990473c5adda26520b309963d78189f11a487a Mon Sep 17 00:00:00 2001
From: Cariad Eccleston <cariad@cariad.earth>
Date: Tue, 19 Dec 2023 16:54:57 +0000
Subject: [PATCH] Yield None when resolving any value from a None record (#38)

---
 rolumns/data_resolver.py    | 9 +++++++++
 tests/test_data_resolver.py | 7 +++++++
 2 files changed, 16 insertions(+)

diff --git a/rolumns/data_resolver.py b/rolumns/data_resolver.py
index 8c64f18..59efb77 100644
--- a/rolumns/data_resolver.py
+++ b/rolumns/data_resolver.py
@@ -19,6 +19,15 @@ def __init__(self, root: Any) -> None:
 
     @staticmethod
     def _resolve(parts: List[str], data: Any) -> Iterable[Optional[Any]]:
+        if data is None:
+            logger.warning(
+                "Cannot use %s as indices of None, so yielding None",
+                parts,
+            )
+
+            yield None
+            return
+
         if isinstance(data, list):
             for d in data:
                 for r in DataResolver._resolve(parts.copy(), d):
diff --git a/tests/test_data_resolver.py b/tests/test_data_resolver.py
index 39563fd..7cc650d 100644
--- a/tests/test_data_resolver.py
+++ b/tests/test_data_resolver.py
@@ -8,6 +8,13 @@
 @mark.parametrize(
     "data, path, expect",
     [
+        (
+            None,
+            "name",
+            [
+                None,
+            ],  # There is no "name" in None.
+        ),
         (
             {},
             "name",