Isol8

1.0.4

ModuleIsolation.cs

using System.Reflection;
using System.Management.Automation;
using System.Runtime.Loader;
using System.IO;
 
namespace PipeHow.Isol8;
 
// Implement interfaces for interacting with loading logic of PowerShell
public abstract class ModuleInitializer : IModuleAssemblyInitializer, IModuleAssemblyCleanup {
    // Create a new custom ALC and provide the directory
    private static Isol8AssemblyLoadContext alc;
    public ModuleInitializer(string assemblyName) {
        ModuleName = assemblyName;
        alc = new Isol8AssemblyLoadContext(dependencyDirectory, assemblyName);
    }
 
    // Runs when Import-Module is run on our module, but in this case also when referred to in NestedModules
    public void OnImport() => AssemblyLoadContext.Default.Resolving += ResolveAssembly;
    // Runs when user runs Remove-Module on our module
    public void OnRemove(PSModuleInfo psModuleInfo) => AssemblyLoadContext.Default.Resolving -= ResolveAssembly;
 
    // Name of initializer assembly
    public static string ModuleName { get; set; }
    // Get directory of this assembly, and use that directory to load dependencies from
    private static readonly string dependencyDirectory = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
 
    // Resolve assembly by name if it's the Isol8 dll being loaded by the default ALC
    // We know it's the default ALC because of OnImport above
    public static Assembly ResolveAssembly(AssemblyLoadContext defaultAlc, AssemblyName assemblyName)
    {
        return assemblyName.Name == ModuleName ?
            alc.LoadFromAssemblyName(assemblyName) :
            null;
    }
}
 
// We create our own ALC by inheriting from AssemblyLoadContext and overriding the Load() method
// We can also change the constructor to take a path which we load from, which we do here
public class Isol8AssemblyLoadContext : AssemblyLoadContext
{
    // The path which we try to load the assemblies from
    private readonly string dependencyDirectory;
     
    // We can call the base constructor to set a name for the ALC
    // There are more options such as marking our ALC as collectible to enable unloading it, but that doesn't work with PowerShell
    public Isol8AssemblyLoadContext(string path, string moduleName) : base(moduleName)
    {
        dependencyDirectory = path;
    }
 
    // Override the Load() method and try to load the module as a DLL file in the provided directory if it exists
    protected override Assembly Load(AssemblyName assemblyName) {
        var assemblyPath = Path.Join(dependencyDirectory, $"{assemblyName.Name}.dll");
 
        // If it exists we can load it from the path
        if (File.Exists(assemblyPath)) {
            return LoadFromAssemblyPath(assemblyPath);
        }
 
        // Returning null once more lets the loader know that we didn't load the module, and lets it try something else
        return null;
    }
}