Add internal engine relocation candidate

internal/engine/composition_fuzz_test.go

@@ -0,0 +1,68 @@
+package engine
+
+import (
+	"bytes"
+	"reflect"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/ConfigKit/internal/document"
+	yamladapter "gitea.maximumdirect.net/eric/ConfigKit/internal/yaml"
+)
+
+func FuzzCompositionAndOverlay(f *testing.F) {
+	for _, seed := range [][2]string{
+		{"{}\n", "{}\n"},
+		{"left: {value: one}\n", "right: [two]\n"},
+		{"shared: {left: one}\n", "shared: {right: two}\n"},
+		{"value: one\n", "value: two\n"},
+	} {
+		f.Add([]byte(seed[0]), []byte(seed[1]))
+	}
+
+	limits := yamladapter.Limits{Depth: 12, Nodes: 256, ParserDepth: 24}
+	f.Fuzz(func(t *testing.T, leftInput, rightInput []byte) {
+		if len(leftInput) > 4<<10 || len(rightInput) > 4<<10 {
+			return
+		}
+		left, leftIssues := yamladapter.Parse(bytes.NewReader(leftInput), "left", limits)
+		right, rightIssues := yamladapter.Parse(bytes.NewReader(rightInput), "right", limits)
+		if len(leftIssues) != 0 || len(rightIssues) != 0 {
+			return
+		}
+		leftBefore, rightBefore := document.Clone(left), document.Clone(right)
+
+		composed, diagnostics := composeDocuments(left, right)
+		if !reflect.DeepEqual(left, leftBefore) || !reflect.DeepEqual(right, rightBefore) {
+			t.Fatal("composition mutated an input document")
+		}
+		if len(diagnostics) == 0 {
+			reversed, reversedDiagnostics := composeDocuments(right, left)
+			if len(reversedDiagnostics) != 0 {
+				t.Fatalf("reversed composition failed: %#v", reversedDiagnostics)
+			}
+			if differences := compareConfigurationValues(composed.root, reversed.root); len(differences) != 0 {
+				t.Fatalf("composition order changed effective values: %#v", differences)
+			}
+			composed.root.Mapping = append(composed.root.Mapping, document.Entry{Key: "fuzz-detachment"})
+			if !reflect.DeepEqual(left, leftBefore) || !reflect.DeepEqual(right, rightBefore) {
+				t.Fatal("composition result aliases an input document")
+			}
+		}
+
+		base, baseDiagnostics := composeDocuments(left)
+		if len(baseDiagnostics) != 0 {
+			t.Fatalf("single accepted mapping did not compose: %#v", baseDiagnostics)
+		}
+		overlaid, overlayDiagnostics := overlayDocuments(base, right)
+		if len(overlayDiagnostics) != 0 {
+			t.Fatalf("accepted mappings did not overlay: %#v", overlayDiagnostics)
+		}
+		if !reflect.DeepEqual(left, leftBefore) || !reflect.DeepEqual(right, rightBefore) {
+			t.Fatal("overlay mutated an input document")
+		}
+		overlaid.root.Mapping = append(overlaid.root.Mapping, document.Entry{Key: "fuzz-detachment"})
+		if !reflect.DeepEqual(left, leftBefore) || !reflect.DeepEqual(right, rightBefore) {
+			t.Fatal("overlay result aliases an input document")
+		}
+	})
+}