Parse nested config sections independently of parent declaration order

confection/_parser.py

@@ -48,7 +48,7 @@ def parse_config(
     result: dict[str, Any] = {}
     section_parts = [section.split(".") for section in config_parser.sections()]
     # Phase 1: Build the skeleton of nested dicts from section names.
-    for parts in section_parts:
+    for parts in sorted(section_parts, key=len):
         node = result
         for part in parts[:-1]:
             node = node.setdefault(part, {}) if part == "*" else node[part]

tests/test_config_basic.py

@@ -7,6 +7,7 @@
 """
 
 from configparser import InterpolationDepthError
+from itertools import permutations
 
 import pytest
 from hypothesis import HealthCheck, given, settings
@@ -21,6 +22,21 @@
 )
 
 
+@pytest.mark.parametrize("order", list(permutations(range(4))))
+def test_sections_can_precede_their_parents(order):
+    sections = [
+        "[training]\nseed = 42",
+        "[training.optimizer]\nrate = 0.01",
+        "[model]\nwidth = 64",
+        "[model.encoder]\ndepth = 2",
+    ]
+    text = "\n\n".join(sections[i] for i in order)
+    assert Config().from_str(text) == {
+        "training": {"seed": 42, "optimizer": {"rate": 0.01}},
+        "model": {"width": 64, "encoder": {"depth": 2}},
+    }
+
+
 @given(config_dicts)
 def test_roundtrip(data):
     """Config.from_str(config.to_str()) should reproduce the original dict."""