[Performance] XmlSerializer instantiated per-call without caching

[mfogliatto]

Description

In XmlConfigurationLoader.ParseConfigFrom(), a new XmlSerializer(typeof(ReferenceCopConfig)) is created every time a config is parsed. XmlSerializer constructor dynamically generates and compiles serialization assemblies, which is expensive (~50-200ms) and causes memory leaks through assembly loading if called repeatedly.

Affected File

src/ReferenceCop/Configuration/XmlConfigurationLoader.cs (line in ParseConfigFrom)

Impact

• Medium. In a Roslyn analyzer context, this is invoked once per compilation. However:
  • In IDE scenarios (VS live analysis), compilations happen frequently on every keystroke
  • The generated assembly is never unloaded, causing gradual memory growth
  • First-compilation startup latency is needlessly high

Suggested Optimization

Cache the serializer as a static field (XmlSerializer for a given type is thread-safe for deserialization):

private static readonly XmlSerializer ConfigSerializer = new XmlSerializer(typeof(ReferenceCopConfig));

private static ReferenceCopConfig ParseConfigFrom(Stream stream)
{
    return (ReferenceCopConfig)ConfigSerializer.Deserialize(stream);
}

This eliminates repeated assembly generation and reduces analyzer startup time.