Add a retarget_snrefs() utility function

odxtools/utils.py

@@ -1,7 +1,48 @@
 # SPDX-License-Identifier: MIT
 import dataclasses
 import re
-from typing import Any, Dict
+from typing import TYPE_CHECKING, Any, Dict, Optional
+
+if TYPE_CHECKING:
+    from .database import Database
+    from .diaglayers.diaglayer import DiagLayer
+    from .snrefcontext import SnRefContext
+
+
+def retarget_snrefs(database: "Database",
+                    diag_layer: "DiagLayer",
+                    context: Optional["SnRefContext"] = None) -> None:
+    """Re-resolve the short name references reachable by a
+    DiagLayer to this DiagLayer
+
+    This implies that after the SNREFs have been retargeted, accessing
+    the resolved objects via a different diagnostic layer might not be
+    correct. E.g.: If the ECU variants "V1" and "V2" are derived from
+    the base variant "BV", BV defines a short name reference to a data
+    object property called "Foo" and V1 and V2 both define a "Foo"
+    DOP, the reference in the base variant to Foo ought to be resolved
+    differently depending on whether it is accessed via V1 or
+    V2. Since odxtools resolves all references ahead of time, a fixed
+    variant has to be chosen. This method allows to switch the variant
+    to another one.
+
+    """
+    from .snrefcontext import SnRefContext
+
+    if context is None:
+        context = SnRefContext()
+
+    if context.diag_layer is None:
+        context.database = database
+        context.diag_layer = diag_layer
+
+    # retarget the objects "owned" by the layer itself
+    diag_layer._resolve_snrefs(context)
+
+    # retarget all parents of the current layer (if any)
+    if (parent_refs := getattr(diag_layer, "parent_refs", None)) is not None:
+        for pr in parent_refs:
+            retarget_snrefs(database, pr.layer, context)
 
 
 def dataclass_fields_asdict(obj: Any) -> Dict[str, Any]: