Index inherited step membership

internal/engine/inheritance_origin_test.go

@@ -2,6 +2,8 @@ package engine
 
 import (
 	"io/fs"
+	"reflect"
+	"slices"
 	"testing"
 	"testing/fstest"
 
@@ -85,6 +87,120 @@ func TestInheritedOriginsKeepSourcePathsPresenceAndIndependentReplacement(t *tes
 	}
 }
 
+func TestProjectedInheritanceStepsMatchScanAndRetainOwnership(t *testing.T) {
+	sourcePath := Keys("source", "a/b", "01")
+	firstLocations := []Location{{SourceID: "first;:source", Line: -1, Column: 2}}
+	secondLocations := []Location{
+		{SourceID: "second:;source", Line: 3, Column: -4},
+		{SourceID: "", Line: -5, Column: 6},
+	}
+	firstTransfer := inheritanceTransfer{
+		from: Keys("source"), to: Keys("middle"), reference: Keys("middle", "extends"), locations: firstLocations,
+	}
+	secondTransfer := inheritanceTransfer{
+		from: Keys("middle"), to: Keys("target"), reference: Keys("target", "extends"), locations: secondLocations,
+	}
+	firstTrace := &inheritanceTrace{transfer: &firstTransfer}
+	chain := &inheritanceTrace{previous: firstTrace, transfer: &secondTransfer}
+	firstStep := InheritanceStep{
+		From: sourcePath, To: Keys("middle", "a/b", "01"), Reference: firstTransfer.reference, Locations: firstLocations,
+	}
+
+	duplicateFirstTransfer := firstTransfer
+	duplicateSecondTransfer := secondTransfer
+	duplicateChain := &inheritanceTrace{
+		previous: &inheritanceTrace{transfer: &duplicateFirstTransfer},
+		transfer: &duplicateSecondTransfer,
+	}
+	reversedLocations := []Location{secondLocations[1], secondLocations[0]}
+	reorderedSecondTransfer := secondTransfer
+	reorderedSecondTransfer.locations = reversedLocations
+	reorderedChain := &inheritanceTrace{
+		previous: &inheritanceTrace{transfer: &duplicateFirstTransfer},
+		transfer: &reorderedSecondTransfer,
+	}
+	origin := Origin{
+		Inheritance: []InheritanceStep{firstStep, firstStep},
+		contributors: []inheritanceContributor{
+			{source: sourcePath, trace: chain},
+			{source: sourcePath, trace: duplicateChain},
+			{source: sourcePath, trace: reorderedChain},
+			{source: sourcePath, trace: chain},
+		},
+	}
+
+	want := projectInheritanceStepsByScan(origin)
+	got := projectInheritanceSteps(origin)
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("projected steps differ from ordered scan:\n got: %#v\nwant: %#v", got, want)
+	}
+	if len(got) != 4 || got[0].From.String() != "/source/a~1b/01" || got[0].To.String() != "/middle/a~1b/01" ||
+		!reflect.DeepEqual(got[0], got[1]) || got[2].To.String() != "/target/a~1b/01" ||
+		!reflect.DeepEqual(got[2].Locations, secondLocations) || !reflect.DeepEqual(got[3].Locations, reversedLocations) {
+		t.Fatalf("unexpected duplicate/order/escape projection: %#v", got)
+	}
+
+	got[0].From.segments[0].key = "mutated"
+	got[2].Locations[0].SourceID = "mutated"
+	if repeated := projectInheritanceSteps(origin); !reflect.DeepEqual(repeated, want) {
+		t.Fatalf("returned steps mutated retained evidence:\n got: %#v\nwant: %#v", repeated, want)
+	}
+}
+
+func TestInheritanceLocationsKeyEncodesOrderedLengthPrefixedValues(t *testing.T) {
+	if inheritanceLocationsKey(nil) != inheritanceLocationsKey([]Location{}) {
+		t.Fatal("nil and empty location lists should encode equally")
+	}
+	values := [][]Location{
+		{{SourceID: "a;1;-2;", Line: -3, Column: 4}},
+		{{SourceID: "a", Line: 1, Column: -2}, {SourceID: ";1;-2;", Line: -3, Column: 4}},
+		{{SourceID: ";1;-2;", Line: -3, Column: 4}, {SourceID: "a", Line: 1, Column: -2}},
+		{{SourceID: "é", Line: -3, Column: 4}},
+		{{SourceID: "e", Line: -3, Column: 4}},
+	}
+	keys := make(map[string]int, len(values))
+	for index, locations := range values {
+		key := inheritanceLocationsKey(locations)
+		if previous, found := keys[key]; found {
+			t.Fatalf("location lists %d and %d encoded identically", previous, index)
+		}
+		keys[key] = index
+	}
+}
+
+func projectInheritanceStepsByScan(origin Origin) []InheritanceStep {
+	steps := cloneInheritanceSteps(origin.Inheritance)
+	for _, contributor := range origin.contributors {
+		var reverse []*inheritanceTrace
+		for link := contributor.trace; link != nil; link = link.previous {
+			reverse = append(reverse, link)
+		}
+		current := contributor.source
+		for index := len(reverse) - 1; index >= 0; index-- {
+			transfer := reverse[index].transfer
+			relative, ok := relativeHistoryPath(transfer.from, current)
+			if !ok {
+				continue
+			}
+			next := appendInheritancePath(transfer.to, relative)
+			step := InheritanceStep{
+				From: current.clone(), To: next.clone(), Reference: transfer.reference.clone(),
+				Locations: cloneLocations(transfer.locations),
+			}
+			if !slices.ContainsFunc(steps, func(existing InheritanceStep) bool {
+				return existing.From.String() == step.From.String() &&
+					existing.To.String() == step.To.String() &&
+					existing.Reference.String() == step.Reference.String() &&
+					slices.Equal(existing.Locations, step.Locations)
+			}) {
+				steps = append(steps, step)
+			}
+			current = next
+		}
+	}
+	return steps
+}
+
 func TestInheritedOriginsRetainChainsAndNestedDestinations(t *testing.T) {
 	first := parseCompositionDocument(t, "source-1", `first:
   enabled: false