Add several tests for application startup

src/Anexia.E5E.Tests/Extensions/HostApplicationBuilderExtensionsTests.cs

@@ -0,0 +1,61 @@
+using System;
+using System.IO;
+using System.Text.Json;
+
+using Anexia.E5E.Exceptions;
+using Anexia.E5E.Extensions;
+using Anexia.E5E.Runtime;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+using Xunit;
+
+namespace Anexia.E5E.Tests.Extensions;
+
+public class HostApplicationBuilderExtensionsTests
+{
+	[Fact]
+	public void EmptyListOfArgumentsThrowsException()
+	{
+		Assert.Throws<E5EMissingArgumentsException>(() =>
+			Host.CreateDefaultBuilder().ConfigureE5E(Array.Empty<string>()).Build());
+	}
+
+	[Fact]
+	public void IncorrectListOfArgumentsThrowsException()
+	{
+		Assert.Throws<E5EMissingArgumentsException>(() =>
+			Host.CreateDefaultBuilder().ConfigureE5E(new[] { "foo", "bar" }).Build());
+	}
+
+	[Fact]
+	public void MetadataIsReturned()
+	{
+		using var _ = Console.Out;
+		using var sw = new StringWriter();
+		Console.SetOut(sw);
+
+		var expected = JsonSerializer.Serialize(new E5ERuntimeMetadata());
+		Host.CreateDefaultBuilder().ConfigureE5E(new[] { "metadata" }).Build().RunE5E();
+
+		Assert.Equal(expected, sw.ToString());
+	}
+
+	[Fact]
+	public void ShouldReadEscapedNullBytes()
+	{
+		var host = Host.CreateDefaultBuilder().ConfigureE5E(new[] { "entrypoint", "\\0", "1", "\\0" }).Build();
+		var got = host.Services.GetRequiredService<E5ERuntimeOptions>();
+		var expected = new E5ERuntimeOptions("entrypoint", "\0", "\0", true, false);
+
+		Assert.Equal(expected, got);
+	}
+
+	[Fact]
+	public void StopsInvocationWithMissingEntrypoint()
+	{
+		var host = Host.CreateDefaultBuilder().ConfigureE5E(new[] { "entrypoint", "\\0", "1", "\\0" }).Build();
+		Assert.Throws<E5EMissingEntrypointException>(() => host.Run());
+	}
+}

src/Anexia.E5E/Extensions/GenericHostExtensions.cs

@@ -0,0 +1,28 @@
+using System.Text.Json;
+
+using Anexia.E5E.Runtime;
+using Anexia.E5E.Serialization;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+namespace Anexia.E5E.Extensions;
+
+public static class GenericHostExtensions
+{
+	public static void RunE5E(this IHost host) => host.RunE5EAsync().GetAwaiter().GetResult();
+
+	public static Task RunE5EAsync(this IHost host, CancellationToken cancellationToken = default)
+	{
+		var runtime = host.Services.GetRequiredService<E5ERuntimeOptions>();
+		if (!runtime.WriteMetadataOnStartup)
+			return host.RunAsync(cancellationToken);
+
+		var lifetime = host.Services.GetRequiredService<IHostApplicationLifetime>();
+		var metadata = JsonSerializer.Serialize(new E5ERuntimeMetadata(), E5EJsonSerializerOptions.Default);
+		Console.Out.Write(metadata);
+		lifetime.StopApplication();
+
+		return Task.CompletedTask;
+	}
+}

src/Anexia.E5E/Extensions/HostApplicationBuilderExtensions.cs

@@ -2,11 +2,15 @@
 
 using Anexia.E5E.Abstractions;
 using Anexia.E5E.Exceptions;
+using Anexia.E5E.Functions;
 using Anexia.E5E.Hosting;
 using Anexia.E5E.Runtime;
+using Anexia.E5E.Serialization;
 
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
 
 namespace Anexia.E5E.Extensions;
 
@@ -23,17 +27,19 @@ public static IHostBuilder ConfigureE5E(this IHostBuilder hb, string[] args)
 			throw new E5EMissingArgumentsException(
 				$"There were no arguments given to the {nameof(ConfigureE5E)} method.");
 
-		if (args[0] == "metadata")
+		hb.ConfigureServices((_, services) =>
 		{
-			var metadata = JsonSerializer.Serialize(new E5ERuntimeMetadata());
-			Console.Out.WriteLine(metadata);
-			Environment.Exit(0);
-			return hb;
-		}
+			services.TryAddEntrypointServiceResolver();
+			services.TryAddSingleton<IConsoleAbstraction, ConsoleAbstraction>();
+		});
+
+		if (args[0] == "metadata")
+			return ConfigureE5E(hb, E5ERuntimeOptions.WriteMetadata);
 
 		if (args.Length != 4)
 			throw new E5EMissingArgumentsException($"Expected exactly four arguments given, got {args.Length}");
 
+
 		var entrypoint = args[0];
 		var stdoutTerminationSequence = args[1].Replace("\\0", "\0");
 		var keepAlive = args[2] == "1";
@@ -47,8 +53,9 @@ public static IHostBuilder ConfigureE5E(this IHostBuilder hb, E5ERuntimeOptions
 	{
 		hb.ConfigureServices((_, services) =>
 		{
-			services.AddSingleton<IConsoleAbstraction, ConsoleAbstraction>();
-			services.AddSingleton(options);
+			services.TryAddEntrypointServiceResolver();
+			services.TryAddSingleton<IConsoleAbstraction, ConsoleAbstraction>();
+			services.TryAddSingleton(options);
 			services.AddHostedService<E5ECommunicationService>();
 		});
 

src/Anexia.E5E/Extensions/ServiceCollectionsHostedServiceExtensions.cs

@@ -38,7 +38,7 @@ public static IServiceCollection AddE5EFunction(this IServiceCollection services
 		return services;
 	}
 
-	private static void TryAddEntrypointServiceResolver(this IServiceCollection services)
+	internal static void TryAddEntrypointServiceResolver(this IServiceCollection services)
 	{
 		services.TryAddScoped<E5EFunctionResolver>(svc => () =>
 		{

src/Anexia.E5E/Runtime/E5ERuntimeOptions.cs

@@ -1,4 +1,7 @@
 namespace Anexia.E5E.Runtime;
 
 public record E5ERuntimeOptions(string Entrypoint, string StdoutTerminationSequence,
-	string DaemonExecutionTerminationSequence, bool KeepAlive);
+	string DaemonExecutionTerminationSequence, bool KeepAlive, bool WriteMetadataOnStartup = false)
+{
+	internal static readonly E5ERuntimeOptions WriteMetadata = new("", "", "", false, true);
+}