migrate: add ETagFor method on TFStateAttrs; simplify etag handling

Replace the verbose LookupTFField call for etag with a direct JSON read
via TFStateAttrs.ETagFor(group, name).

Co-authored-by: Isaac

Author: denik

bundle/migrate/build_state.go

@@ -204,14 +204,12 @@ func BuildStateFromTF(
 			return fmt.Errorf("%s: unresolved references: %v", node, sv.Refs)
 		}
 
-		// Handle etag for dashboards: look it up directly from TF state attributes.
+		// Handle etag for dashboards: read it directly from TF state attributes.
 		// The "etag" field is a computed TF attribute not present in the bundle config,
 		// so it does not flow through PrepareState/ExtractReferences.
-		if etag, err := LookupTFField(tfAttrs, group, srcName, structpath.NewStringKey(nil, "etag")); err == nil && etag != nil {
-			if etagStr, ok := etag.(string); ok && etagStr != "" {
-				if err := structaccess.Set(sv.Value, structpath.NewStringKey(nil, "etag"), etagStr); err != nil {
-					return fmt.Errorf("%s: cannot set etag: %w", node, err)
-				}
+		if etag := tfAttrs.ETagFor(group, srcName); etag != "" {
+			if err := structaccess.Set(sv.Value, structpath.NewStringKey(nil, "etag"), etag); err != nil {
+				return fmt.Errorf("%s: cannot set etag: %w", node, err)
 			}
 		}
 

bundle/migrate/tf_state.go

@@ -25,6 +25,26 @@ var tfStateFieldAliases = map[string]map[string]string{
 // TFStateAttrs maps (tfResourceType → resourceName → raw JSON attributes).
 type TFStateAttrs map[string]map[string]json.RawMessage
 
+// ETagFor returns the "etag" attribute for a bundle resource, or "" if absent.
+// Reads directly from the raw JSON without full path translation.
+func (a TFStateAttrs) ETagFor(group, name string) string {
+	tfType, ok := terraform.GroupToTerraformName[group]
+	if !ok {
+		return ""
+	}
+	raw, ok := a[tfType][name]
+	if !ok {
+		return ""
+	}
+	var v struct {
+		Etag string `json:"etag,omitempty"`
+	}
+	if err := json.Unmarshal(raw, &v); err != nil {
+		return ""
+	}
+	return v.Etag
+}
+
 // TFState holds everything parsed from a single terraform state file read.
 type TFState struct {
 	// Attrs maps (tfResourceType → resourceName → raw JSON attributes).