Detect inheritance directives without paths

docs/roadmap/implementation.md

@@ -120,7 +120,7 @@ Roadmap candidate 1. Owner: `internal/engine/metadata.go`.
 Validate: `go test ./internal/engine -run 'Metadata|Presence|Explicit|Inherited'`,
 relevant root facade tests, and the everyday check. No allocation assertion.
 
-## Stage 3: Detect inheritance without constructing paths
+## Stage 3: Detect inheritance without constructing paths — Complete
 
 Roadmap candidate 9. Owner: `internal/engine/inheritance_load.go`.
 

internal/engine/inheritance_load.go

@@ -3,14 +3,28 @@ package engine
 import "gitea.maximumdirect.net/eric/ConfigKit/internal/document"
 
 func containsInheritanceDirective(root *document.Node) bool {
-	found := false
-	walkDocument(root, Path{}, func(path Path, _ *document.Node) {
-		if len(path.segments) != 0 && path.segments[len(path.segments)-1].kind == pathSegmentKey &&
-			path.segments[len(path.segments)-1].key == inheritanceKey {
-			found = true
+	var visit func(*document.Node) bool
+	visit = func(node *document.Node) bool {
+		if node == nil {
+			return false
 		}
-	})
-	return found
+		switch node.Kind {
+		case document.Mapping:
+			for _, entry := range node.Mapping {
+				if entry.Key == inheritanceKey || visit(entry.Value) {
+					return true
+				}
+			}
+		case document.Sequence:
+			for _, child := range node.Sequence {
+				if visit(child) {
+					return true
+				}
+			}
+		}
+		return false
+	}
+	return visit(root)
 }
 
 func inheritanceVersionDiagnostic(rule *VersionRule, expanded *inheritanceScope) *Diagnostic {

internal/engine/inheritance_test.go

@@ -121,6 +121,24 @@ func TestSiblingInheritanceRejectsInvalidRelationships(t *testing.T) {
 	}
 }
 
+func TestLoadDetectsInvalidInheritanceInsideSequence(t *testing.T) {
+	input := []byte(`items:
+  - child: {extends: true}
+`)
+	result, err := testLoad[map[string]any](Bytes("nested-inheritance.yml", input), Options[map[string]any]{})
+	if result != nil || err == nil {
+		t.Fatalf("result, err = %#v, %v; want invalid nested inheritance", result, err)
+	}
+	loadError, ok := err.(*LoadError)
+	if !ok {
+		t.Fatalf("error type = %T, want *LoadError", err)
+	}
+	diagnostics := loadError.Diagnostics()
+	if len(diagnostics) != 1 || diagnostics[0].Code != CodeInheritanceInvalid || diagnostics[0].Path.String() != "/items/0/child/extends" {
+		t.Fatalf("diagnostics = %#v", diagnostics)
+	}
+}
+
 func TestSiblingInheritanceDetectsDeepCycleWithoutRecursiveDependencyWalk(t *testing.T) {
 	const count = 2048
 	entries := make([]document.Entry, count)