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Make group node id escaping injective

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Uri.EscapeDataString maps every unpaired surrogate to %EF%BF%BD, so distinct
values shared one node id. An unpaired surrogate now spells %uXXXX.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This commit is contained in:
Meta Vens 2026-09-29 14:03:58 +02:00
commit 384c7df02b
1 changed files with 22 additions and 1 deletions
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23
src/GameCult.Caching/CultInspectorModel.cs
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@ -3,6 +3,7 @@ using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using MessagePack;
namespace GameCult.Caching
@ -653,7 +654,27 @@ namespace GameCult.Caching
// A node's id is its members' value identities, so it survives relabelling: a ref by key, an enum by its underlying
// value, anything else by the value's invariant string.
private static string GroupId(IReadOnlyList<CultInspectorMember> members, IReadOnlyList<object?> values) =>
string.Join("/", values.Select((value, i) => members[i].Name + "=" + Uri.EscapeDataString(IdentityOf(value))));
string.Join("/", values.Select((value, i) => members[i].Name + "=" + EscapeIdentity(IdentityOf(value))));
// Injective: text is spelled as Uri.EscapeDataString spells it, which turns '/' and '%' into %XX; an unpaired
// surrogate, which that method would flatten to U+FFFD, becomes %uXXXX, a form no escaped run contains.
private static string EscapeIdentity(string identity)
{
var escaped = new StringBuilder();
var run = 0;
for (var i = 0; i < identity.Length; i++)
{
if (char.IsHighSurrogate(identity[i]) && i + 1 < identity.Length && char.IsLowSurrogate(identity[i + 1]))
i++;
else if (char.IsSurrogate(identity[i]))
{
escaped.Append(Uri.EscapeDataString(identity.Substring(run, i - run))).Append("%u").Append(((int)identity[i]).ToString("X4"));
run = i + 1;
}
}
return escaped.Append(Uri.EscapeDataString(identity.Substring(run))).ToString();
}
private static string IdentityOf(object? value) =>
value switch