Compare canonical paths by token spelling

internal/engine/path.go

@@ -128,6 +128,45 @@ func clonePathSegments(segments []pathSegment, extra int) []pathSegment {
 	return cloned
 }
 
+func pathTokenSpellingEqual(left, right pathSegment) bool {
+	switch {
+	case left.kind == pathSegmentIndex && right.kind == pathSegmentIndex:
+		return left.index == right.index
+	case left.kind == pathSegmentIndex:
+		return pathIndexSpellingEqual(left.index, right.key)
+	case right.kind == pathSegmentIndex:
+		return pathIndexSpellingEqual(right.index, left.key)
+	default:
+		return left.key == right.key
+	}
+}
+
+func pathIndexSpellingEqual(index int, token string) bool {
+	var scratch [20]byte
+	spelling := strconv.AppendInt(scratch[:0], int64(index), 10)
+	if len(spelling) != len(token) {
+		return false
+	}
+	for i, character := range spelling {
+		if character != token[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func pathSpellingEqual(left, right Path) bool {
+	if len(left.segments) != len(right.segments) {
+		return false
+	}
+	for i, segment := range left.segments {
+		if !pathTokenSpellingEqual(segment, right.segments[i]) {
+			return false
+		}
+	}
+	return true
+}
+
 func escapePathToken(token string) string {
 	token = strings.ReplaceAll(token, "~", "~0")
 	return strings.ReplaceAll(token, "/", "~1")