/// <summary>
/// Finds the assembly locations for all assemblies containing plugins of the specified type.
/// </summary>
/// <param name="pluginPath">The path to plugins.</param>
/// <param name="sharedTypes">A list of shared types to be used when loading plugins into custom assembly contexts.</param>
/// <returns>A list of assembly locations.</returns>
public IEnumerable <string> FindPluginAssemblies(string pluginPath, Type[] sharedTypes)
{
_logger.LogInformation(InformationMessages.SearchingPluginPath, typeof(TPlugin).Name, pluginPath);
var assemblyPaths = new List <string>();
// Check directory
var path = new DirectoryInfo(pluginPath);
if (path.Exists)
{
var files = path.GetFiles(_options.FindPattern, SearchOption.AllDirectories);
if (files.Any())
{
_logger.LogInformation(InformationMessages.LibraryCountFoundInPath, files.Length, path.FullName);
_logger.LogInformation(InformationMessages.ScanningLibraries);
foreach (var libPath in files)
{
_logger.LogTrace(TraceMessages.CheckingLibraryForPlugins, libPath.FullName);
// Create plugin assembly load context to hold the assemblies and dependencies per library
var pluginContext = new PluginAssemblyLoadContext(libPath.FullName, sharedTypes);
// Don't load the library containing the plugin type itself into the plugin AssemblyLoadContext,
// otherwise the IsAssignableFrom won't return a match, because the same assembly in different
// contexts have types that are not the same as each other when comparing in .NET Core.
if (libPath.Name != new FileInfo(typeof(TPlugin).Assembly.Location).Name)
{
try
{
var assembly = pluginContext.LoadFromAssemblyPath(libPath.FullName);
foreach (var type in assembly.GetExportedTypes().Where(t => !t.IsAbstract))
{
var interfaceType = typeof(TPlugin);
if (interfaceType.IsAssignableFrom(type))
{
_logger.LogTrace(TraceMessages.FoundPlugin, type.FullName, libPath.FullName);
assemblyPaths.Add(type.Assembly.Location);
}
}
}
catch (FileNotFoundException e)
{
_logger.LogDebug(TraceMessages.IgnoringLibraryMissingDependencies, libPath.FullName);
_logger.LogDebug(e.ToString());
}
catch (BadImageFormatException e)
{
_logger.LogDebug(TraceMessages.IgnoringLibraryNotDotNetImage, libPath.FullName);
_logger.LogDebug(e.ToString());
}
catch (FileLoadException e)
{
_logger.LogDebug(TraceMessages.IgnoringLibraryFileLoadFailed, libPath.FullName);
_logger.LogDebug(e.ToString());
}
}
// Unload context
pluginContext.Unload();
// Without collecting deterministically, some directories with lots of DLL's can
// eventually cause an Internal CLR error (segmentation fault). This may still occur
// but this alleviates the issue. Always use a search pattern (--find-pattern arg) to
// reduce number of DLL's to scan.
GC.Collect();
GC.WaitForPendingFinalizers();
}
}
else
{
_logger.LogInformation(InformationMessages.LibrariesNotFoundInPath, path.FullName);
}
}
else
{
_logger.LogError(ErrorMessages.PluginPathDoesNotExist, path.FullName);
}
return(assemblyPaths);
}