feat: Ignore port-forwarding extra host in reuse hash (#1689)

Author: HofmeisterAn

src/Testcontainers/Configurations/Commons/JsonIgnoreRuntimeExtraHosts.cs

@@ -0,0 +1,29 @@
+namespace DotNet.Testcontainers.Configurations
+{
+  using System;
+  using System.Collections.Generic;
+  using System.Linq;
+  using System.Text.Json;
+  using System.Text.Json.Serialization;
+
+  /// <summary>
+  /// Excludes the port-forwarding extra host entry (host.testcontainers.internal)
+  /// from the reuse hash, its IP changes every test session, which would otherwise
+  /// make identical configurations appear different.
+  /// </summary>
+  internal sealed class JsonIgnoreRuntimeExtraHosts : JsonConverter<IEnumerable<string>>
+  {
+    private const string PortForwardingHostEntry = "host.testcontainers.internal:";
+
+    public override IEnumerable<string> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+      return JsonSerializer.Deserialize<IEnumerable<string>>(ref reader);
+    }
+
+    public override void Write(Utf8JsonWriter writer, IEnumerable<string> value, JsonSerializerOptions options)
+    {
+      var extraHosts = value.Where(host => !host.StartsWith(PortForwardingHostEntry, StringComparison.OrdinalIgnoreCase)).OrderBy(host => host);
+      JsonSerializer.Serialize(writer, extraHosts, options);
+    }
+  }
+}

src/Testcontainers/Configurations/Commons/JsonIgnoreRuntimeResourceLabels.cs

@@ -6,6 +6,10 @@ namespace DotNet.Testcontainers.Configurations
   using DotNet.Testcontainers.Clients;
   using DotNet.Testcontainers.Containers;
 
+  /// <summary>
+  /// Excludes session-specific labels from the reuse hash so containers with
+  /// identical configuration are still recognized as reusable across test sessions.
+  /// </summary>
   internal sealed class JsonIgnoreRuntimeResourceLabels : JsonOrderedKeysConverter
   {
     private static readonly ISet<string> IgnoreLabels = new HashSet<string>

src/Testcontainers/Configurations/Containers/ContainerConfiguration.cs

@@ -208,6 +208,7 @@ public ContainerConfiguration(IContainerConfiguration oldValue, IContainerConfig
     public IEnumerable<string> NetworkAliases { get; }
 
     /// <inheritdoc />
+    [JsonConverter(typeof(JsonIgnoreRuntimeExtraHosts))]
     public IEnumerable<string> ExtraHosts { get; }
 
     /// <inheritdoc />