From 0144b0d1c944434585bd348bcd25fb96a772b86a Mon Sep 17 00:00:00 2001
From: Max Zuev <mail@thenno.me>
Date: Fri, 3 Nov 2023 22:53:57 +0100
Subject: [PATCH] BI-5002: allow to use field name as a default fallback cfg
 key (#69)

---
 .../dl_configs/settings_loaders/loader_env.py | 12 ++++++----
 .../unit/test_settings_loader_env.py          | 23 +++++++++++++++++++
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/lib/dl_configs/dl_configs/settings_loaders/loader_env.py b/lib/dl_configs/dl_configs/settings_loaders/loader_env.py
index ec2e6b226..904d632b2 100644
--- a/lib/dl_configs/dl_configs/settings_loaders/loader_env.py
+++ b/lib/dl_configs/dl_configs/settings_loaders/loader_env.py
@@ -488,11 +488,15 @@ def build_composite_extractor(
                 else:
                     raise SettingsLoadingException(f"Unexpected signature of fallback factory for {field}")
 
-            elif cls.is_sub_settings_field(field) and default is not None and default is not NOT_SET:
-                field_default = getattr(default, field_name)
-
             else:
-                field_default = NOT_SET
+                field_default = getattr(fallback_cfg, field_s_meta.name, NOT_SET)
+                if (
+                    field_default is NOT_SET
+                    and cls.is_sub_settings_field(field)
+                    and default is not None
+                    and default is not NOT_SET
+                ):
+                    field_default = getattr(default, field_name)
 
             child_extractor: SDictExtractor
 
diff --git a/lib/dl_configs/dl_configs_tests/unit/test_settings_loader_env.py b/lib/dl_configs/dl_configs_tests/unit/test_settings_loader_env.py
index 23653a235..0506a5975 100644
--- a/lib/dl_configs/dl_configs_tests/unit/test_settings_loader_env.py
+++ b/lib/dl_configs/dl_configs_tests/unit/test_settings_loader_env.py
@@ -812,3 +812,26 @@ class TypedSettings(SettingsBase):
             b=b_value,
         ),
     )
+
+
+def test_default_cfg_key_name(temp_file_factory):
+    @attr.s(frozen=True)
+    class Settings:
+        TEST_KEY: str = s_attrib("TEST_KEY", missing="default_value")  # type: ignore
+
+    class Fallback:
+        TEST_KEY = "test_value"
+
+    perform_loader_env_check(
+        {},
+        fallback_env=Fallback,
+        expected_settings=Settings(
+            TEST_KEY="test_value",
+        ),
+    )
+    perform_loader_env_check(
+        {},
+        expected_settings=Settings(
+            TEST_KEY="default_value",
+        ),
+    )