fix: support reference to fields with null values

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)
 

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:

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