Fix bug when deep copying full config with missing parent (#3009)

hydra/_internal/instantiate/_instantiate2.py

@@ -151,17 +151,24 @@ def _deep_copy_full_config(subconfig: Any) -> Any:
         return copy.deepcopy(subconfig)
 
     full_key = subconfig._get_full_key(None)
-    if full_key:
-        full_config_copy = copy.deepcopy(subconfig._get_root())
-        if OmegaConf.is_list(subconfig._get_parent()):
-            # OmegaConf has a bug where _get_full_key doesn't add [] if the parent
-            # is a list, eg. instead of foo[0], it'll return foo0
-            index = subconfig._key()
-            full_key = full_key[: -len(str(index))] + f"[{index}]"
-        return OmegaConf.select(full_config_copy, full_key)
-    else:
+    if not full_key:
+        return copy.deepcopy(subconfig)
+
+    if OmegaConf.is_list(subconfig._get_parent()):
+        # OmegaConf has a bug where _get_full_key doesn't add [] if the parent
+        # is a list, eg. instead of foo[0], it'll return foo0
+        index = subconfig._key()
+        full_key = full_key[: -len(str(index))] + f"[{index}]"
+    root = subconfig._get_root()
+    full_key = full_key.replace(root._get_full_key(None) or "", "", 1)
+    if OmegaConf.select(root, full_key) is not subconfig:
+        # The parent chain and full key are not consistent so don't
+        # try to copy the full config
         return copy.deepcopy(subconfig)
 
+    full_config_copy = copy.deepcopy(root)
+    return OmegaConf.select(full_config_copy, full_key)
+
 
 def instantiate(
     config: Any,

tests/instantiate/__init__.py

@@ -8,6 +8,7 @@
 from omegaconf import MISSING, DictConfig, ListConfig
 
 from hydra.types import TargetConf
+from hydra.utils import instantiate
 from tests.instantiate.module_shadowed_by_function import a_function
 
 module_shadowed_by_function = a_function
@@ -418,6 +419,19 @@ class NestedConf:
     b: Any = field(default_factory=lambda: User(name="b", age=2))
 
 
+class TargetWithInstantiateInInit:
+    def __init__(
+        self, user_config: Optional[DictConfig], user: Optional[User] = None
+    ) -> None:
+        if user:
+            self.user = user
+        else:
+            self.user = instantiate(user_config)
+
+    def __eq__(self, other: Any) -> bool:
+        return self.user.__eq__(other.user)
+
+
 def recisinstance(got: Any, expected: Any) -> bool:
     """Compare got with expected type, recursively on dict and list."""
     if not isinstance(got, type(expected)):

tests/instantiate/test_instantiate.py

@@ -43,6 +43,7 @@
     SimpleClassNonPrimitiveConf,
     SimpleClassPrimitiveConf,
     SimpleDataClass,
+    TargetWithInstantiateInInit,
     Tree,
     TreeConf,
     UntypedPassthroughClass,
@@ -571,6 +572,30 @@ def test_none_cases(
             OmegaConf.create({"unique_id": 5}),
             id="interpolation_from_parent_with_interpolation",
         ),
+        param(
+            DictConfig(
+                {
+                    "username": "test_user",
+                    "node": {
+                        "_target_": "tests.instantiate.TargetWithInstantiateInInit",
+                        "_recursive_": False,
+                        "user_config": {
+                            "_target_": "tests.instantiate.User",
+                            "name": "${foo_b.username}",
+                            "age": 40,
+                        },
+                    },
+                    "foo_b": {
+                        "username": "${username}",
+                    },
+                }
+            ),
+            {},
+            TargetWithInstantiateInInit(
+                user_config=None, user=User(name="test_user", age=40)
+            ),
+            id="target_with_instantiate_in_init",
+        ),
     ],
 )
 def test_interpolation_accessing_parent(