[Performance] XmlConfigurationLoader creates new XmlSerializer on every instantiation

[mfogliatto]

Description

XmlConfigurationLoader.ParseConfigFrom() creates a new XmlSerializer(typeof(ReferenceCopConfig)) each time it's called. XmlSerializer constructors dynamically generate and compile a serialization assembly at runtime.

Affected Files

• src/ReferenceCop/Configuration/XmlConfigurationLoader.cs (line ~48, ParseConfigFrom method)

Impact

• Startup cost: Each new XmlSerializer() triggers runtime code generation (~50-200ms for complex types), adding latency during analyzer initialization
• Memory leak in .NET Framework: Dynamically generated assemblies are never unloaded in .NET Framework, causing a slow memory leak if the analyzer is invoked repeatedly (e.g., in IDE real-time analysis scenarios)
• Repeated allocation: In MSBuild/Roslyn scenarios where the analyzer initializes per-project, this compounds across the build

Suggested Optimization

Cache the serializer as a static field:

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

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

The XmlSerializer(Type) constructor is thread-safe for the simple single-type form, and the cached instance can be safely shared.