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Changed file name of IAbstractFactory interface to match with conventions; refactored the assembly loading code into a separate class using an interface, this allows unit testing to simulate assembly loading errors easily and might help the actual application to act on assembly load errors if so required; all classes in the Nuclex.Support.Plugins namespace now have 100% test coverage

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git-svn-id: file:///srv/devel/repo-conversion/nusu@104 d2e56fa2-650e-0410-a79f-9358c0239efd
This commit is contained in:
Markus Ewald 2008-12-09 19:41:43 +00:00
parent 88b51ef0fa
commit 447fe2aea7
7 changed files with 330 additions and 57 deletions
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6
Nuclex.Support.csproj
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@ -123,16 +123,14 @@
<Compile Include="Source\PathHelper.Test.cs">
<DependentUpon>PathHelper.cs</DependentUpon>
</Compile>
<Compile Include="Source\Plugins\AbstractFactory.cs" />
<Compile Include="Source\Plugins\AbstractFactory.Test.cs">
<DependentUpon>AbstractFactory.cs</DependentUpon>
</Compile>
<Compile Include="Source\Plugins\IAbstractFactory.cs" />
<Compile Include="Source\Plugins\Employer.Test.cs">
<DependentUpon>Employer.cs</DependentUpon>
</Compile>
<Compile Include="Source\Plugins\FactoryEmployer.Test.cs">
<DependentUpon>FactoryEmployer.cs</DependentUpon>
</Compile>
<Compile Include="Source\Plugins\IAssemblyLoader.cs" />
<Compile Include="Source\Plugins\InstanceEmployer.Test.cs">
<DependentUpon>InstanceEmployer.cs</DependentUpon>
</Compile>

0
Source/Plugins/AbstractFactory.cs → Source/Plugins/IAbstractFactory.cs
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23
Source/Plugins/AbstractFactory.Test.cs → Source/Plugins/IAssemblyLoader.cs
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@ -19,21 +19,22 @@ License along with this library
#endregion
using System;
using System.IO;
#if UNITTEST
using NUnit.Framework;
using NUnit.Framework.SyntaxHelpers;
using System.Collections.Generic;
using System.Reflection;
namespace Nuclex.Support.Plugins {
/// <summary>Unit Test for the abstract factory interface</summary>
[TestFixture]
public class AbtractFactoryTest {
/// <summary>Interface for an assembly loading helper</summary>
public interface IAssemblyLoader {
/// <summary>Tries to loads an assembly from a file</summary>
/// <param name="path">Path to the file that is loaded as an assembly</param>
/// <param name="loadedAssembly">
/// Output parameter that receives the loaded assembly or null
/// </param>
/// <returns>True if the assembly was loaded successfully, otherwise false</returns>
bool TryLoadFile(string path, out Assembly loadedAssembly);
}
} // namespace Nuclex.Support.Plugins
#endif // UNITTEST

128
Source/Plugins/PluginHost.Test.cs
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@ -20,6 +20,7 @@ License along with this library
using System;
using System.IO;
using System.Reflection;
#if UNITTEST
@ -29,8 +30,133 @@ using NUnit.Framework.SyntaxHelpers;
namespace Nuclex.Support.Plugins {
/// <summary>Unit Test for the plugin host class</summary>
[TestFixture]
[TestFixture, NoPlugin] // NoPlugin is used in one of the unit tests
public class PluginHostTest {
#region class FailingEmployer
/// <summary>Employer that unexpectedly fails to employ a given type</summary>
private class FailingEmployer : Employer {
/// <summary>Employs the specified plugin type</summary>
/// <param name="type">Type to be employed</param>
public override void Employ(Type type) {
if(type.Equals(typeof(PluginRepository))) {
throw new InvalidOperationException();
}
}
}
#endregion // class FailingEmployer
/// <summary>Tests whether the simple constructor is working</summary>
[Test]
public void TestSimpleConstructor() {
new PluginHost(new FactoryEmployer<PluginHostTest>());
}
/// <summary>Tests whether the full constructor is working</summary>
[Test]
public void TestFullConstructor() {
new PluginHost(new FactoryEmployer<PluginHostTest>(), new PluginRepository());
}
/// <summary>
/// Tests whether the AddAssembly() method works by adding the test assembly
/// itself to the repository
/// </summary>
[Test]
public void TestFullConstructorWithPreloadedAssembly() {
PluginRepository testRepository = new PluginRepository();
FactoryEmployer<PluginRepository> testEmployer = new FactoryEmployer<PluginRepository>();
// Might also use Assembly.GetCallingAssembly() here, but this leads to the exe of
// the unit testing tool
Assembly self = Assembly.GetAssembly(GetType());
testRepository.AddAssembly(self);
PluginHost testHost = new PluginHost(testEmployer, testRepository);
Assert.AreEqual(1, testEmployer.Factories.Count);
}
/// <summary>
/// Verifies that the plugin host correctly stores the provided repository
/// </summary>
[Test]
public void TestRepositoryStorage() {
PluginRepository testRepository = new PluginRepository();
FactoryEmployer<PluginRepository> testEmployer = new FactoryEmployer<PluginRepository>();
PluginHost testHost = new PluginHost(testEmployer, testRepository);
Assert.AreSame(testRepository, testHost.Repository);
}
/// <summary>
/// Verifies that the plugin host correctly stores the provided employer
/// </summary>
[Test]
public void TestEmployerStorage() {
PluginRepository testRepository = new PluginRepository();
FactoryEmployer<PluginRepository> testEmployer = new FactoryEmployer<PluginRepository>();
PluginHost testHost = new PluginHost(testEmployer, testRepository);
Assert.AreSame(testEmployer, testHost.Employer);
}
/// <summary>
/// Tests whether the plugin host noticed when new assemblies are loaded into
/// the repository
/// </summary>
[Test]
public void TestAssemblyLoading() {
PluginRepository testRepository = new PluginRepository();
FactoryEmployer<PluginRepository> testEmployer = new FactoryEmployer<PluginRepository>();
PluginHost testHost = new PluginHost(testEmployer, testRepository);
// Might also use Assembly.GetCallingAssembly() here, but this leads to the exe of
// the unit testing tool
Assembly self = Assembly.GetAssembly(GetType());
testRepository.AddAssembly(self);
Assert.AreEqual(1, testEmployer.Factories.Count);
}
/// <summary>
/// Tests whether the plugin host isolates the caller from an exception when the
/// employer fails to employ a type in the assembly
/// </summary>
[Test]
public void TestAssemblyLoadingWithEmployFailure() {
PluginRepository testRepository = new PluginRepository();
PluginHost testHost = new PluginHost(new FailingEmployer(), testRepository);
// Might also use Assembly.GetCallingAssembly() here, but this leads to the exe of
// the unit testing tool
Assembly self = Assembly.GetAssembly(GetType());
testRepository.AddAssembly(self);
}
/// <summary>
/// Verifies that the plugin host ignores types which have the NoPluginAttribute
/// assigned to them
/// </summary>
[Test]
public void TestAssemblyLoadingWithNoPluginAttribute() {
PluginRepository testRepository = new PluginRepository();
FactoryEmployer<PluginHostTest> testEmployer = new FactoryEmployer<PluginHostTest>();
PluginHost testHost = new PluginHost(testEmployer, testRepository);
// Might also use Assembly.GetCallingAssembly() here, but this leads to the exe of
// the unit testing tool
Assembly self = Assembly.GetAssembly(GetType());
testRepository.AddAssembly(self);
Assert.AreEqual(0, testEmployer.Factories.Count);
}
}
} // namespace Nuclex.Support.Plugins

23
Source/Plugins/PluginHost.cs
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@ -19,6 +19,7 @@ License along with this library
#endregion
using System;
using System.Diagnostics;
using System.Reflection;
namespace Nuclex.Support.Plugins {
@ -83,11 +84,9 @@ namespace Nuclex.Support.Plugins {
// Types that have been tagged with the [NoPlugin] attribute will be ignored
object[] attributes = type.GetCustomAttributes(true);
for(int index = 0; index < attributes.Length; ++index) {
if(attributes[index] is NoPluginAttribute) {
if(containsNoPluginAttribute(attributes)) {
continue;
}
}
// Type seems to be acceptable, assess and possibly employ it
try {
@ -96,14 +95,26 @@ namespace Nuclex.Support.Plugins {
}
}
catch(Exception exception) {
System.Console.WriteLine(
"Could not employ " + type.ToString() + ": " + exception.Message
);
Trace.WriteLine("Could not employ " + type.ToString() + ": " + exception.Message);
}
}
}
/// <summary>
/// Determines whether the specifies list of attributes contains a NoPluginAttribute
/// </summary>
/// <param name="attributes">List of attributes to check</param>
/// <returns>True if the list contained a NoPluginAttribute, false otherwise</returns>
private static bool containsNoPluginAttribute(object[] attributes) {
for(int index = 0; index < attributes.Length; ++index) {
if(attributes[index] is NoPluginAttribute) {
return true;
}
}
return false;
}
/// <summary>Employs and manages types in the loaded plugin assemblies</summary>
private Employer employer;
/// <summary>Repository containing all plugins loaded, shared with other hosts</summary>

81
Source/Plugins/PluginRepository.Test.cs
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@ -19,6 +19,7 @@ License along with this library
#endregion
using System;
using System.Diagnostics;
using System.IO;
using System.Reflection;
@ -53,6 +54,40 @@ namespace Nuclex.Support.Plugins {
#endregion // interface IProgressTrackerSubscriber
#region class TestAssemblyLoader
/// <summary>Special assembly loader for the unit test</summary>
public class TestAssemblyLoader : PluginRepository.DefaultAssemblyLoader {
/// <summary>Loads an assembly from a file system path</summary>
/// <param name="path">Path the assembly will be loaded from</param>
/// <returns>The loaded assembly</returns>
protected override Assembly LoadAssemblyFromFile(string path) {
switch(path) {
case "DllNotFound": {
Trace.WriteLine("Simulating DllNotFoundException for unit test");
throw new DllNotFoundException();
}
case "UnauthorizedAccess": {
Trace.WriteLine("Simulating UnauthorizedAccessException for unit test");
throw new UnauthorizedAccessException();
}
case "BadImageFormat": {
Trace.WriteLine("Simulating BadImageFormatException for unit test");
throw new BadImageFormatException();
}
case "IO": {
Trace.WriteLine("Simulating IOException for unit test");
throw new IOException();
}
default: { return Assembly.LoadFile(path); }
}
}
}
#endregion // class TestAssemblyLoader
/// <summary>
/// Tests whether the default constructor of the plugin repository class works
/// </summary>
@ -81,6 +116,8 @@ namespace Nuclex.Support.Plugins {
Assembly self = Assembly.GetAssembly(GetType());
testRepository.AddFiles(self.Location);
Assert.AreEqual(1, testRepository.LoadedAssemblies.Count);
}
/// <summary>
@ -118,6 +155,50 @@ namespace Nuclex.Support.Plugins {
mockery.VerifyAllExpectationsHaveBeenMet();
}
/// <summary>
/// Verifies that no exceptions come through when a DllNotFoundException is thrown
/// during assembly loading
/// </summary>
[Test]
public void TestDllNotFoundExceptionDuringAssemblyLoad() {
TestAssemblyLoader loader = new TestAssemblyLoader();
Assembly loadedAssembly;
Assert.IsFalse(loader.TryLoadFile("DllNotFound", out loadedAssembly));
}
/// <summary>
/// Verifies that no exceptions come through when a UnauthorizedAccessException is
/// thrown during assembly loading
/// </summary>
[Test]
public void TestUnauthorizedAccessExceptionDuringAssemblyLoad() {
TestAssemblyLoader loader = new TestAssemblyLoader();
Assembly loadedAssembly;
Assert.IsFalse(loader.TryLoadFile("UnauthorizedAccess", out loadedAssembly));
}
/// <summary>
/// Verifies that no exceptions come through when a BadImageFormatException is
/// thrown during assembly loading
/// </summary>
[Test]
public void TestBadImageFormatExceptionDuringAssemblyLoad() {
TestAssemblyLoader loader = new TestAssemblyLoader();
Assembly loadedAssembly;
Assert.IsFalse(loader.TryLoadFile("BadImageFormat", out loadedAssembly));
}
/// <summary>
/// Verifies that no exceptions come through when an IOException is
/// thrown during assembly loading
/// </summary>
[Test]
public void TestIOExceptionDuringAssemblyLoad() {
TestAssemblyLoader loader = new TestAssemblyLoader();
Assembly loadedAssembly;
Assert.IsFalse(loader.TryLoadFile("IO", out loadedAssembly));
}
/// <summary>Mocks a subscriber for the events of a plugin repository</summary>
/// <param name="mockery">Mockery to create an event subscriber in</param>
/// <param name="repository">Repository to subscribe the mocked subscriber to</param>

124
Source/Plugins/PluginRepository.cs
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@ -20,8 +20,9 @@ License along with this library
using System;
using System.Collections.Generic;
using System.Reflection;
using System.Diagnostics;
using System.IO;
using System.Reflection;
namespace Nuclex.Support.Plugins {
@ -33,12 +34,94 @@ namespace Nuclex.Support.Plugins {
/// </remarks>
public class PluginRepository {
#region class DefaultAssemblyLoader
/// <summary>Default assembly loader used to read assemblies from files</summary>
public class DefaultAssemblyLoader : IAssemblyLoader {
/// <summary>Initializes a new default assembly loader</summary>
/// <remarks>
/// Made protected to provide users with a small incentive for using
/// the Instance property instead of creating new instances all around.
/// </remarks>
protected DefaultAssemblyLoader() { }
/// <summary>Loads an assembly from a file system path</summary>
/// <param name="path">Path the assembly will be loaded from</param>
/// <returns>The loaded assembly</returns>
protected virtual Assembly LoadAssemblyFromFile(string path) {
return Assembly.LoadFile(path);
}
/// <summary>Tries to loads an assembly from a file</summary>
/// <param name="path">Path to the file that is loaded as an assembly</param>
/// <param name="loadedAssembly">
/// Output parameter that receives the loaded assembly or null
/// </param>
/// <returns>True if the assembly was loaded successfully, otherwise false</returns>
public bool TryLoadFile(string path, out Assembly loadedAssembly) {
// A lot of errors can occur when attempting to load an assembly...
try {
loadedAssembly = LoadAssemblyFromFile(path);
return true;
}
// File not found - Most likely a missing dependency of the assembly we
// attempted to load since the assembly itself has been found by the GetFiles() method
catch(DllNotFoundException) {
Trace.WriteLine(
"Assembly '" + path + "' or one of its dependencies is missing"
);
}
// Unauthorized acccess - Either the assembly is not trusted because it contains
// code that imposes a security risk on the system or a user rights problem
catch(UnauthorizedAccessException) {
Trace.WriteLine(
"Not authorized to load assembly '" + path + "', " +
"possible rights problem"
);
}
// Bad image format - This exception is often thrown when the assembly we
// attempted to load requires a different version of the .NET framework
catch(BadImageFormatException) {
Trace.WriteLine(
"'" + path + "' is not a .NET assembly, requires a different version " +
"of the .NET Runtime or does not support the current instruction set (x86/x64)"
);
}
// Unknown error - Our last resort is to show a default error message
catch(Exception exception) {
Trace.WriteLine(
"Failed to load plugin assembly '" + path + "': " + exception.Message
);
}
loadedAssembly = null;
return false;
}
/// <summary>The only instance of the DefaultAssemblyLoader</summary>
public static readonly DefaultAssemblyLoader Instance =
new DefaultAssemblyLoader();
}
#endregion // class DefaultAssemblyLoader
/// <summary>Triggered whenever a new assembly is loaded into this repository</summary>
public event AssemblyLoadEventHandler AssemblyLoaded;
/// <summary>Initializes a new instance of the plugin repository</summary>
public PluginRepository() {
public PluginRepository() : this(DefaultAssemblyLoader.Instance) { }
/// <summary>Initializes a new instance of the plugin repository</summary>
/// <param name="loader">
/// Loader to use for loading assemblies into this repository
/// </param>
public PluginRepository(IAssemblyLoader loader) {
this.assemblies = new List<Assembly>();
this.assemblyLoader = loader;
}
/// <summary>Loads all plugins matching a wildcard specification</summary>
@ -63,38 +146,9 @@ namespace Nuclex.Support.Plugins {
string[] assemblyFiles = Directory.GetFiles(directory, search);
foreach(string assemblyFile in assemblyFiles) {
// A lot of errors can occur when attempting to load an assembly...
try {
AddAssembly(Assembly.LoadFile(assemblyFile));
}
// File not found - Most likely a missing dependency of the assembly we
// attempted to load since the assembly itself has been found by the GetFiles() method
catch(DllNotFoundException) {
Console.WriteLine(
"Assembly '" + assemblyFile + "' or one of its dependencies is missing"
);
}
// Unauthorized acccess - Either the assembly is not trusted because it contains
// code that imposes a security risk on the system or a user rights problem
catch(UnauthorizedAccessException) {
Console.WriteLine(
"Not authorized to load assembly '" + assemblyFile + "', " +
"possible rights problem"
);
}
// Bad image format - This exception is often thrown when the assembly we
// attempted to load requires a different version of the .NET framework
catch(BadImageFormatException) {
Console.WriteLine(
"'" + assemblyFile +"' is not a .NET assembly, requires a different version " +
"of the .NET Runtime or does not support the current instruction set (x86/x64)"
);
}
// Unknown error - Our last resort is to show a default error message
catch(Exception exception) {
Console.WriteLine(
"Failed to load plugin assembly '" + assemblyFile + "': " + exception.Message
);
Assembly loadedAssembly;
if(this.assemblyLoader.TryLoadFile(assemblyFile, out loadedAssembly)) {
AddAssembly(loadedAssembly);
}
}
@ -121,6 +175,8 @@ namespace Nuclex.Support.Plugins {
/// <summary>Loaded plugin assemblies</summary>
private List<Assembly> assemblies;
/// <summary>Takes care of loading assemblies for the repositories</summary>
private IAssemblyLoader assemblyLoader;
}