Preserve matched history for removed fields

internal/engine/metadata.go

@@ -49,7 +49,7 @@ func (m Metadata) effectiveField(path Path) (FieldInfo, bool) {
 // Unknown and invalid paths return nil.
 func (m Metadata) History(path Path) []Change {
 	model := m.historyEvidence()
-	if model == nil || !model.hasObservedShape(path) {
+	if model == nil {
 		return nil
 	}
 	selections := model.selectHistory(path)

internal/engine/resolution_remediation_test.go

@@ -0,0 +1,42 @@
+package engine
+
+import "testing"
+
+func TestMovedRemovedFieldHasConsistentHistory(t *testing.T) {
+	type config struct {
+		Items []map[string]any `yaml:"items"`
+	}
+	definition := DefinitionWithSequenceIdentityRegistrations(Definition[config]{
+		Resolve: func(value *config, r *Resolution) error {
+			delete(value.Items[0], "extra")
+			value.Items[0], value.Items[1] = value.Items[1], value.Items[0]
+			r.RecordNormalization(Keys("items"), "remove field and reorder")
+			return nil
+		},
+	}, []SequenceIdentityRegistrationInput{{ExactPath: pathPointer(Keys("items")), IdentityFields: []string{"id"}}})
+	result, err := testLoad(Bytes("records", []byte("items: [{id: a, extra: own}, {id: b}]\n")), Options[config]{Definition: definition})
+	if err != nil {
+		t.Fatal(err)
+	}
+	path := Keys("items").Index(1).Key("extra")
+	if _, found := result.Metadata().Lookup(path); found {
+		t.Fatal("removed field is effective")
+	}
+	explanation, found := result.Inspection.Explain(path)
+	if !found || len(explanation.History) != 2 {
+		t.Fatalf("explanation = %#v, %t", explanation, found)
+	}
+	history := result.Metadata().History(path)
+	if len(history) != 2 || history[0].Origin.Layer != LayerMain || history[1].Origin.Operation != ChangeNormalization {
+		t.Fatalf("metadata history = %#v", history)
+	}
+	last := explanation.History[1]
+	if last.Before.YAML != "own\n" || last.After.Present {
+		t.Fatalf("removal = %#v", last)
+	}
+	for _, unknown := range []Path{Keys("items", "1", "extra"), Keys("items").Index(1).Key("unknown")} {
+		if history := result.Metadata().History(unknown); len(history) != 0 {
+			t.Fatalf("unexpected history for %s: %#v", unknown.String(), history)
+		}
+	}
+}