Project version protections through item placement

internal/engine/directives.go

@@ -163,26 +163,54 @@ func nestedDirectiveDiagnostics(node *document.Node, current Path) []Diagnostic
 }
 
 func fragmentVersionClaim(root *document.Node, rule *VersionRule) *document.Node {
+	return fragmentVersionClaimProjected(root, rule, -1, nil)
+}
+
+func fragmentVersionClaimProjected(root *document.Node, rule *VersionRule, sourceIndex int, ranges []sequenceRange) *document.Node {
 	if rule == nil {
 		return nil
 	}
 	current := root
+	currentPath := Path{}
 	if len(rule.Path.segments) == 0 {
 		return current
 	}
 	for _, segment := range rule.Path.segments {
-		if current.Kind != document.Mapping {
+		switch current.Kind {
+		case document.Mapping:
+			if segment.kind == pathSegmentIndex {
+				return current
+			}
+			index := documentEntryIndex(current.Mapping, segment.key)
+			if index < 0 {
+				return nil
+			}
+			current = current.Mapping[index].Value
+			currentPath = currentPath.Key(segment.key)
+		case document.Sequence:
+			if segment.kind != pathSegmentIndex {
+				return current
+			}
+			index := segment.index
+			for _, assigned := range ranges {
+				if assigned.sourceIndex != sourceIndex || assigned.path.String() != currentPath.String() {
+					continue
+				}
+				if index < assigned.start || index >= assigned.end {
+					return nil
+				}
+				index -= assigned.start
+				break
+			}
+			if index < 0 || index >= len(current.Sequence) {
+				return nil
+			}
+			current = current.Sequence[index]
+			currentPath = currentPath.Index(index)
+		default:
+			// A scalar or null at an ancestor replaces the protected subtree.
 			return current
 		}
-		if segment.kind == pathSegmentIndex {
-			return nil
-		}
-		key := segment.key
-		index := documentEntryIndex(current.Mapping, key)
-		if index < 0 {
-			return nil
-		}
-		current = current.Mapping[index].Value
 	}
 	return current
 }