feat: Add support for dependency injection via constructor

.github/workflows/dotnetcore.yml

@@ -30,4 +30,5 @@ jobs:
         dotnet build ./samples/Plugins/PersonPlugin/Example.PersonPlugin.csproj -c Release
         dotnet build ./samples/Plugins/JsonPlugin/Example.JsonPlugin.csproj -c Release
         dotnet build ./samples/Plugins/OldJsonPlugin/Example.OldJsonPlugin.csproj -c Release
+        dotnet build ./samples/Plugins/DependencyInjectionPlugin/Example.DependencyInjectionPlugin.csproj -c Release
         dotnet test ./samples/Test/Example.Test.csproj -c Release

CPlugin.Net.sln

@@ -17,6 +17,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Example.HostWebApi", "sampl
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Example.SharedEntities", "samples\SharedEntities\Example.SharedEntities.csproj", "{F66A1430-3F32-4E25-8966-54D502D216DE}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Example.DependencyInjectionPlugin", "samples\Plugins\DependencyInjectionPlugin\Example.DependencyInjectionPlugin.csproj", "{28065D77-B890-47DE-B695-04E388176925}"
+EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Example.JsonPlugin", "samples\Plugins\JsonPlugin\Example.JsonPlugin.csproj", "{C5B8EF73-7DB5-441F-AE38-0988751A896B}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Example.OldJsonPlugin", "samples\Plugins\OldJsonPlugin\Example.OldJsonPlugin.csproj", "{1ADE3B86-00EF-4976-8B67-09B360B149FA}"
@@ -98,6 +100,10 @@ Global
 		{18534944-583B-4924-AC5B-E0655FD92AAC}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{18534944-583B-4924-AC5B-E0655FD92AAC}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{18534944-583B-4924-AC5B-E0655FD92AAC}.Release|Any CPU.Build.0 = Release|Any CPU
+		{1E64908D-DC48-4B83-BB25-CF36821EB37F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{1E64908D-DC48-4B83-BB25-CF36821EB37F}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{1E64908D-DC48-4B83-BB25-CF36821EB37F}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{1E64908D-DC48-4B83-BB25-CF36821EB37F}.Release|Any CPU.Build.0 = Release|Any CPU
 		{0F27C776-F284-4C94-86C9-0FF089245E13}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{0F27C776-F284-4C94-86C9-0FF089245E13}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{0F27C776-F284-4C94-86C9-0FF089245E13}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -122,10 +128,10 @@ Global
 		{0BCD3305-F0D5-43E6-B879-EEF0827558A8}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{0BCD3305-F0D5-43E6-B879-EEF0827558A8}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{0BCD3305-F0D5-43E6-B879-EEF0827558A8}.Release|Any CPU.Build.0 = Release|Any CPU
-		{1E64908D-DC48-4B83-BB25-CF36821EB37F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{1E64908D-DC48-4B83-BB25-CF36821EB37F}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{1E64908D-DC48-4B83-BB25-CF36821EB37F}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{1E64908D-DC48-4B83-BB25-CF36821EB37F}.Release|Any CPU.Build.0 = Release|Any CPU
+		{28065D77-B890-47DE-B695-04E388176925}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{28065D77-B890-47DE-B695-04E388176925}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{28065D77-B890-47DE-B695-04E388176925}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{28065D77-B890-47DE-B695-04E388176925}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

samples/Contracts/ITestService.cs

@@ -0,0 +1,6 @@
+namespace Example.Contracts;
+
+public interface ITestService
+{
+    string Execute();
+}

samples/HostApplications/WebApi/Controllers/ServiceController.cs

@@ -0,0 +1,10 @@
+namespace Example.HostWebApi.Controllers;
+
+[ApiController]
+[Route("[controller]")]
+public class ServiceController
+{
+    [HttpGet]
+    public ActionResult<string> Get(IEnumerable<ITestService> services)
+        => services.First().Execute();
+}

samples/HostApplications/WebApi/Program.cs

@@ -18,6 +18,8 @@
     mvcBuilder.PartManager.ApplicationParts.Add(new AssemblyPart(assembly));
 }
 
+builder.Services.AddSubtypesOf<ITestService>(ServiceLifetime.Transient);
+
 // Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddSwaggerGen(options =>

samples/HostApplications/WebApi/appsettings.json

@@ -6,8 +6,10 @@
     }
   },
   "AllowedHosts": "*",
+  "ServiceName": "TestService",
   "Plugins": [
     "Example.AppointmentPlugin.dll",
-    "Example.PersonPlugin.dll"
+    "Example.PersonPlugin.dll",
+    "Example.DependencyInjectionPlugin.dll"
   ]
 }

samples/Plugins/DependencyInjectionPlugin/Example.DependencyInjectionPlugin.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <OutDir>$(WebApiProjectDir)</OutDir>
+    <OutputType>Library</OutputType>
+    <NoDefaultLaunchSettingsFile>true</NoDefaultLaunchSettingsFile>
+  </PropertyGroup>
+
+</Project>

samples/Plugins/DependencyInjectionPlugin/GlobalUsings.cs

@@ -0,0 +1,3 @@
+global using Example.Contracts;
+global using CPlugin.Net;
+global using Example.DependencyInjectionPlugin;

samples/Plugins/DependencyInjectionPlugin/TestService.cs

@@ -0,0 +1,23 @@
+[assembly: Plugin(typeof(TestService))]
+
+namespace Example.DependencyInjectionPlugin;
+
+public class TestService : ITestService
+{
+    private readonly ILogger<TestService> _logger;
+    private readonly IConfiguration _configuration;
+
+    public TestService(
+        ILogger<TestService> logger, 
+        IConfiguration configuration)
+    {
+        _logger = logger;
+        _configuration = configuration;
+    }
+
+    public string Execute()
+    {
+        _logger.LogInformation("TestService");
+        return _configuration["ServiceName"];
+    }
+}

samples/Test/WebApi/Get.cs

@@ -102,4 +102,23 @@ public async Task Get_WhenWeatherForecastAreObtained_ShouldReturnsHttpStatusCode
         result.IsSuccess.Should().BeTrue();
         result.Data.Should().HaveCount(expectedWeatherForecast);
     }
+
+    [Test]
+    public async Task Get_WhenServiceNameIsObtained_ShouldReturnsHttpStatusCodeOk()
+    {
+        // Arrange
+        using var factory = new WebApplicationFactory<Program>();
+        var client = factory.CreateClient();
+        var expectedServiceName = "TestService";
+
+        // Act
+        var httpResponse = await client.GetAsync("/Service");
+        var result = await httpResponse
+            .Content
+            .ReadAsStringAsync();
+
+        // Asserts
+        httpResponse.StatusCode.Should().Be(HttpStatusCode.OK);
+        result.Should().Be(expectedServiceName);
+    }
 }

src/Core/CPlugin.Net.csproj

@@ -26,6 +26,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Logging.Console" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
   </ItemGroup>
 
   <ItemGroup>

src/Core/ServiceCollectionExtensions.cs

@@ -0,0 +1,76 @@
+using Microsoft.Extensions.DependencyInjection;
+using System.Reflection;
+
+namespace CPlugin.Net;
+
+/// <summary>
+/// Extension methods for adding services to an <see cref="IServiceCollection"/>.
+/// </summary>
+public static class CPluginServiceCollectionExtensions
+{
+    /// <summary>
+    /// Adds the subtypes that implement the contract specified by <typeparamref name="TSupertype"/> 
+    /// to the service collection, using the assemblies loaded by <see cref="PluginLoader"/>.
+    /// </summary>
+    /// <typeparam name="TSupertype">
+    /// The type of contract (base type) shared between the host application and the plugins.
+    /// </typeparam>
+    /// <param name="services">
+    /// The <see cref="IServiceCollection"/> to add the service to.
+    /// </param>
+    /// <param name="serviceLifetime">
+    /// Specifies the lifetime of the services to be added to the service collection.
+    /// </param>
+    /// <remarks>
+    /// This method uses the <see cref="PluginAttribute"/> type to add the implementations of the contract 
+    /// to the service collection, so plugins must use it.
+    /// </remarks>
+    /// <returns>
+    /// A reference to this instance after the operation has completed.
+    /// </returns>
+    public static IServiceCollection AddSubtypesOf<TSupertype>(
+        this IServiceCollection services,
+        ServiceLifetime serviceLifetime) where TSupertype : class
+        => services.AddSubtypesOf<TSupertype>(PluginLoader.Assemblies, serviceLifetime);
+
+    // This method is only to be used for testing.
+    // This way you don't have to depend on the plugin loader when testing.
+    internal static IServiceCollection AddSubtypesOf<TSupertype>(
+        this IServiceCollection services,
+        IEnumerable<Assembly> assemblies,
+        ServiceLifetime serviceLifetime) where TSupertype : class
+    {
+        if (assemblies is null)
+            throw new ArgumentNullException(nameof(assemblies));
+
+        foreach (Assembly assembly in assemblies)
+        {
+            var pluginAttributes = assembly.GetCustomAttributes<PluginAttribute>();
+            foreach (PluginAttribute pluginAttribute in pluginAttributes)
+            {
+                Type implementationType = pluginAttribute.PluginType;
+                if (typeof(TSupertype).IsAssignableFrom(implementationType))
+                {
+                    services.AddService(
+                        serviceType: typeof(TSupertype), 
+                        implementationType, 
+                        serviceLifetime);
+                }
+            }
+        }
+
+        return services;
+    }
+
+    private static IServiceCollection AddService(
+        this IServiceCollection services,
+        Type serviceType,
+        Type implementationType,
+        ServiceLifetime serviceLifetime) => serviceLifetime switch
+        {
+            ServiceLifetime.Singleton => services.AddSingleton(serviceType, implementationType),
+            ServiceLifetime.Transient => services.AddTransient(serviceType, implementationType),
+            ServiceLifetime.Scoped    => services.AddScoped(serviceType, implementationType),
+            _ => throw new NotSupportedException($"Lifetime '{serviceLifetime}' is not supported.")
+        };
+}

src/Core/TypeFinder.cs

@@ -28,9 +28,6 @@ public static class TypeFinder
     /// or if no assembly uses <see cref="PluginAttribute"/>.
     /// <para>This method never returns <c>null</c>.</para>
     /// </returns>
-    /// <exception cref="ArgumentNullException">
-    /// <c>assemblies</c> is <c>null</c>.
-    /// </exception>
     public static IEnumerable<TSupertype> FindSubtypesOf<TSupertype>() where TSupertype : class
         => FindSubtypesOf<TSupertype>(PluginLoader.Assemblies);
 
@@ -55,9 +52,9 @@ private static IEnumerable<TSupertype> GetSubtypesOf<TSupertype>(IEnumerable<Ass
             var pluginAttributes = assembly.GetCustomAttributes<PluginAttribute>();
             foreach (PluginAttribute pluginAttribute in pluginAttributes)
             {
-                Type type = pluginAttribute.PluginType;
-                if (typeof(TSupertype).IsAssignableFrom(type))
-                    yield return (TSupertype)Activator.CreateInstance(type);
+                Type implementationType = pluginAttribute.PluginType;
+                if (typeof(TSupertype).IsAssignableFrom(implementationType))
+                    yield return (TSupertype)Activator.CreateInstance(implementationType);
             }
         }
     }