From f45eb3776875ce0ba7434b620d54e8c17d5c8894 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Perceval=20Wajsb=C3=BCrt?= <perceval.wajsburt@aphp.fr>
Date: Wed, 15 Jan 2025 09:55:15 +0100
Subject: [PATCH] fix: support reference to fields with null values

---
 changelog.md                  |  8 ++++++--
 confit/config.py              |  4 ++--
 tests/test_config_instance.py | 11 +++++++++++
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/changelog.md b/changelog.md
index 85f316c..d131bf4 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,11 +1,15 @@
 # Changelog
 
+## Unreleased
+
+- Allow larger than 4096 bytes config files
+- Escape tabs and newline when serializing to a config file
+- Fix an infinite loop that occured when resolving a reference to a field with a null value
+
 ## v0.7.3 (2024-12-11)
 
 - Support interpolated seed in the config file (as a reminder, the seed is treated specifically by confit to initialize random generators **before** any object is resolved)
 - Support if/else expressions in interpolation, and only resolve the relevant branch
-- Allow larger than 4096 bytes config files
-- Escape tabs and newline when serializing to a config file
 
 ## v0.7.2 (2024-11-23)
 
diff --git a/confit/config.py b/confit/config.py
index fccd6f4..0297598 100644
--- a/confit/config.py
+++ b/confit/config.py
@@ -461,10 +461,10 @@ def rec(obj, loc: Tuple[Union[str, int]] = ()):
             elif isinstance(obj, tuple):
                 resolved = tuple(rec(v, (*loc, i)) for i, v in enumerate(obj))
             elif isinstance(obj, Reference):
-                resolved = None
-                while resolved is None:
+                while True:
                     try:
                         resolved = resolve_reference(obj)
+                        break
                     except (KeyError, NameError):
                         raise MissingReference(obj)
             else:
diff --git a/tests/test_config_instance.py b/tests/test_config_instance.py
index 4634f26..a5c4195 100644
--- a/tests/test_config_instance.py
+++ b/tests/test_config_instance.py
@@ -741,3 +741,14 @@ def test_newline_serialization():
 
 """
     )
+
+
+def test_null_reference():
+    config = Config.from_yaml_str(
+        """
+test:
+    a: null
+    b: ${test.a}
+"""
+    ).resolve(registry=registry)
+    assert config["test"]["b"] is None