Old-style "user" section raises a warning.

datacube/cfg/api.py

@@ -95,7 +95,12 @@ def __init__(
         self.allow_envvar_overrides = text is None and raw_dict is None
 
         if raw_dict is None and text is None:
-            text = find_config(paths)
+            # No explict config passed in.  Check for ODC_CONFIG environmnet variables
+            if os.environ.get("ODC_CONFIG"):
+                text = os.environ["ODC_CONFIG"]
+            else:
+                # Read config text from config file
+                text = find_config(paths)
 
         self.raw_text = text
         self.raw_config = raw_dict
@@ -209,6 +214,10 @@ def __init__(self,
         self._allow_envvar_overrides: bool = allow_env_overrides
         self._normalised: dict[str, Any] = {}
 
+        if name == "user" and "default_environment" in  raw:
+            warnings.warn("The 'default_environment' setting in the 'user' section is no longer supported - "
+                          "please refer to the documentation for more information")
+
         # Aliases are handled here, the alias OptionHandler is a place-holder.
         if "alias" in self._raw:
             alias = self._raw['alias']

tests/test_cfg.py

@@ -186,6 +186,23 @@ def test_invalid_env():
         """)
 
 
+def test_oldstyle_cfg():
+    from datacube.cfg.api import ODCConfig, ConfigException
+    with pytest.warns(UserWarning, match=r'default_environment.*no longer supported'):
+        cfg = ODCConfig(text="""
+default:
+    index_driver: memory
+env2:
+    index_driver: memory
+env3:
+    index_driver: memory
+user:
+    default_environment: env3
+"""
+        )
+        assert cfg[None]._name == 'default'
+
+
 def test_invalid_option():
     from datacube.cfg.opt import ODCOptionHandler, ConfigException
     mockenv = MagicMock()