Index collection prefixes for path correspondence

docs/roadmap/remediation.md

@@ -176,7 +176,15 @@ change was added to provide.
 
 ## Finding 4 — Correspondence lookup repeatedly serializes growing path prefixes
 
-**Priority:** P2. **Status:** Open.
+**Priority:** P2. **Status:** Complete.
+
+Completion: eligible collection prefixes now use the existing prefix index.
+Translation formats the requested pointer once, retains concrete path-kind
+checks, and copies the resulting path independently. No-eligible cases return
+positionally without formatting prefixes; no-registration loads skip matching
+construction entirely. Cloning rebuilds an independently owned index. Existing
+matching/history/ownership coverage and a numeric-key/escaped-key regression
+passed, along with `./scripts/check.sh`.
 
 **Code:** [correspondence translations](../../internal/engine/resolution_correspondence.go),
 `entryPath` at lines 96–125 and `finalPath` at lines 129–156; consumers include

internal/engine/resolution_correspondence.go

@@ -13,28 +13,45 @@ type collectionCorrespondence struct {
 }
 
 type resolutionCorrespondence struct {
-	collections map[string]collectionCorrespondence
+	collections        map[string]collectionCorrespondence
+	prefix             pathPrefixIndex
+	indexedCollections []string
 }
 
 func (c resolutionCorrespondence) clone() resolutionCorrespondence {
-	result := resolutionCorrespondence{collections: make(map[string]collectionCorrespondence, len(c.collections))}
-	for key, collection := range c.collections {
+	var result resolutionCorrespondence
+	for _, collection := range c.collections {
 		collection.path = collection.path.clone()
 		collection.entryToFinal = append([]int(nil), collection.entryToFinal...)
 		collection.finalToEntry = append([]int(nil), collection.finalToEntry...)
-		result.collections[key] = collection
+		result.indexCollection(collection)
 	}
 	return result
 }
 
+func (c *resolutionCorrespondence) indexCollection(collection collectionCorrespondence) {
+	if c.collections == nil {
+		c.collections = make(map[string]collectionCorrespondence)
+	}
+	pointer := collection.path.String()
+	c.collections[pointer] = collection
+	if collection.eligible {
+		c.prefix.insert(pointer, len(c.indexedCollections))
+		c.indexedCollections = append(c.indexedCollections, pointer)
+	}
+}
+
 func buildResolutionCorrespondence(entry, final *document.Node, policy sequencePolicy) resolutionCorrespondence {
-	result := resolutionCorrespondence{collections: make(map[string]collectionCorrespondence)}
+	var result resolutionCorrespondence
+	if policy.selectorTrie == nil {
+		return result
+	}
 	var indexes mappingIndex
 	var visit func(*document.Node, *document.Node, Path)
 	visit = func(before, after *document.Node, path Path) {
 		if fields, registered := policy.identityFieldsAt(path); registered &&
 			((before != nil && before.Kind == document.Sequence) || (after != nil && after.Kind == document.Sequence)) {
-			result.collections[path.String()] = matchResolutionCollection(before, after, path, fields)
+			result.indexCollection(matchResolutionCollection(before, after, path, fields))
 			return
 		}
 		if before != nil && before.Kind == document.Mapping {
@@ -94,64 +111,55 @@ func matchResolutionCollection(before, after *document.Node, path Path, fields [
 // entryPath translates a surviving final record prefix; additions have no entry.
 // Paths outside eligible collections and wholly absent final positions stay positional.
 func (c resolutionCorrespondence) entryPath(path Path) (Path, bool) {
-	if !path.valid() {
-		return Path{}, false
-	}
-	for depth := 0; depth < len(path.segments); depth++ {
-		prefix := Path{segments: path.segments[:depth]}
-		collection, found := c.collections[prefix.String()]
-		if !found || !collection.eligible {
-			continue
-		}
-		compatible := true
-		for i, segment := range collection.path.segments {
-			if segment.kind == pathSegmentKey && path.segments[i].kind == pathSegmentIndex {
-				compatible = false
-				break
-			}
-		}
-		index, ok := schemaIndex(path.segments[depth])
-		if !compatible || !ok || index >= len(collection.finalToEntry) {
-			continue
-		}
-		previous := collection.finalToEntry[index]
-		if previous < 0 {
-			return Path{}, false
-		}
-		translated := path.clone()
-		translated.segments[depth] = pathSegment{kind: pathSegmentIndex, index: previous}
-		return translated, true
-	}
-	return path.clone(), true
+	return c.translate(path, false)
 }
 
 // finalPath translates historical record descendants without matching removals.
 func (c resolutionCorrespondence) finalPath(path Path) (Path, bool) {
+	return c.translate(path, true)
+}
+
+func (c resolutionCorrespondence) translate(path Path, toFinal bool) (Path, bool) {
 	if !path.valid() {
 		return Path{}, false
 	}
-	for depth := 0; depth < len(path.segments); depth++ {
-		prefix := Path{segments: path.segments[:depth]}
-		collection, found := c.collections[prefix.String()]
-		if !found || !collection.eligible {
-			continue
+	translated := path.clone()
+	if len(c.indexedCollections) == 0 {
+		return translated, true
+	}
+	matched, handled := true, false
+	c.prefix.visitAncestors(path.String(), func(id int) {
+		if handled {
+			return
+		}
+		collection := c.collections[c.indexedCollections[id]]
+		depth := len(collection.path.segments)
+		if depth >= len(path.segments) {
+			return
 		}
 		for i, segment := range collection.path.segments {
 			if segment.kind == pathSegmentKey && path.segments[i].kind == pathSegmentIndex {
-				return path.clone(), true
+				return
 			}
 		}
 		index, ok := schemaIndex(path.segments[depth])
-		if !ok || index >= len(collection.entryToFinal) {
-			continue
+		indices := collection.finalToEntry
+		if toFinal {
+			indices = collection.entryToFinal
 		}
-		current := collection.entryToFinal[index]
+		if !ok || index >= len(indices) {
+			return
+		}
+		handled = true
+		current := indices[index]
 		if current < 0 {
-			return Path{}, false
+			matched = false
+			return
 		}
-		translated := path.clone()
 		translated.segments[depth] = pathSegment{kind: pathSegmentIndex, index: current}
-		return translated, true
+	})
+	if !matched {
+		return Path{}, false
 	}
-	return path.clone(), true
+	return translated, true
 }

internal/engine/resolution_remediation_test.go

@@ -143,3 +143,45 @@ func TestCyclicMatchingProtectsRemovedAndDerivedValues(t *testing.T) {
 		t.Fatal("effective rendering leaked")
 	}
 }
+
+func TestCorrespondenceIndexPreservesPathShapes(t *testing.T) {
+	destination := Keys("groups", "0", "a/b~")
+	policy, diagnostics := compileSequenceIdentityPolicy([]sequenceIdentityRegistration{{
+		selector: sequenceIdentitySelector{
+			literalSequenceSelector("groups"), literalSequenceSelector("0"), literalSequenceSelector("a/b~"),
+		},
+		identityFields: []string{"id"},
+	}})
+	if len(diagnostics) != 0 {
+		t.Fatal(diagnostics)
+	}
+	before := parseCompositionDocument(t, "before", "groups: {'0': {'a/b~': [{id: a}, {id: b}]}}")
+	after := parseCompositionDocument(t, "after", "groups: {'0': {'a/b~': [{id: b}, {id: a}, {id: new}]}}")
+	matching := buildResolutionCorrespondence(before, after, policy)
+	parsed, err := ParsePath("/groups/0/a~1b~0/0/field")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, path := range []Path{destination.Index(0).Key("field"), parsed} {
+		entry, found := matching.entryPath(path)
+		if !found || entry.String() != destination.Index(1).Key("field").String() {
+			t.Fatalf("entry = %s, %t", entry.String(), found)
+		}
+		final, found := matching.finalPath(entry)
+		if !found || final.String() != path.String() {
+			t.Fatalf("round trip = %s, %t", final.String(), found)
+		}
+	}
+	for _, path := range []Path{
+		Keys("groups").Index(0).Key("a/b~").Index(0),
+		destination.Key("0"), destination.Index(8), destination,
+	} {
+		entry, found := matching.entryPath(path)
+		if !found || entry.String() != path.String() {
+			t.Fatalf("positional path %s became %s, %t", path.String(), entry.String(), found)
+		}
+	}
+	if _, found := matching.entryPath(destination.Index(2)); found {
+		t.Fatal("new identity acquired entry evidence")
+	}
+}

internal/engine/secret_propagation.go

@@ -43,7 +43,7 @@ func closeSecretDependenciesWithCorrespondence(paths map[string]Path, sensitive
 	}
 
 	var projected map[string]bool
-	if len(correspondence.collections) != 0 {
+	if len(correspondence.indexedCollections) != 0 {
 		projected = make(map[string]bool, len(paths))
 	}
 	project := func(path Path) {