使用.NET源生成器(SG)實現一個自動注入的生成器

DI依賴注入對我們後端程序員來說肯定是基礎中的基礎了,我們經常會使用下面的代碼注入相關的service

services.AddScoped<Biwen.AutoClassGen.TestConsole.Services.TestService2>();
services.AddTransient<Biwen.AutoClassGen.TestConsole.Services.TestService2>();
services.AddScoped<Biwen.AutoClassGen.TestConsole.Services.ITest2Service, Biwen.AutoClassGen.TestConsole.Services.TestService2>();
services.AddScoped<Biwen.AutoClassGen.TestConsole.Services.TestService3>();
services.AddScoped<Biwen.AutoClassGen.TestConsole.Services2.MyService>();
services.AddScoped<Biwen.AutoClassGen.TestConsole.Services.TestService>();
services.AddSingleton<Biwen.AutoClassGen.TestConsole.Services.ITestService, Biwen.AutoClassGen.TestConsole.Services.TestService>();
services.AddScoped<Biwen.AutoClassGen.TestConsole.Services.ITest2Service, Biwen.AutoClassGen.TestConsole.Services.TestService>();

對於上面的代碼如果代碼量很大而且隨着項目的迭代可能會堆積更多的代碼,對於很多程序員來說第一想到的可能是透過反射批量注入,當然這也是最簡單最直接的方式,今天我們使用源生成器的方式實現這個功能, 使用源生成器的方式好處還是有的比如AOT需求,極致性能要求

實現這個功能的具體步驟:

定義Attribute-標註Attribute-遍歷代碼中標註Attribute的metadata集合-生成源代碼

首先我們定義一個Attribute用於標註需要注入的類

namespace Biwen.AutoClassGen.Attributes
{
    using System;
    /// <summary>
    /// 服務生命週期
    /// </summary>
    public enum ServiceLifetime
    {
        Singleton = 1,
        Transient = 2,
        Scoped = 4,
    }

    [AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = false)]
    public class AutoInjectAttribute : Attribute
    {
        public ServiceLifetime ServiceLifetime { get; set; }
        public Type BaseType { get; set; }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="baseType">NULL表示服務自身</param>
        /// <param name="serviceLifetime">服務生命週期</param>
        public AutoInjectAttribute(Type baseType = null, ServiceLifetime serviceLifetime = ServiceLifetime.Scoped)
        {
            ServiceLifetime = serviceLifetime;
            BaseType = baseType;
        }
    }

//C#11及以上的版本支持泛型Attribute
#if NET7_0_OR_GREATER
    [AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = false)]
    public class AutoInjectAttribute<T> : AutoInjectAttribute
    {
        public AutoInjectAttribute(ServiceLifetime serviceLifetime = ServiceLifetime.Scoped) : base(typeof(T), serviceLifetime)
        {
        }
    }
#endif
}

通過上面定義的Attribute我們就可以給我們的服務打上標記了

[AutoInject<TestService>]
[AutoInject<ITestService>(ServiceLifetime.Singleton)]
[AutoInject<ITest2Service>(ServiceLifetime.Scoped)]
public class TestService : ITestService, ITest2Service
{
	public string Say(string message)
	{
		return $"hello {message}";
	}
	public string Say2(string message)
	{
		return message;
	}
}

[AutoInject]
[AutoInject(serviceLifetime: ServiceLifetime.Transient)]
[AutoInject(typeof(ITest2Service), ServiceLifetime.Scoped)]
public class TestService2 : ITest2Service
{
	public string Say2(string message)
	{
		return message;
	}
}

接下來就是Roslyn分析C#語法解析代碼片段:
實現源生成器的唯一接口IIncrementalGenerator 實現Initialize方法:


private const string AttributeValueMetadataNameInject = "AutoInject";

/// <summary>
/// 泛型AutoInjectAttribute
/// </summary>
private const string GenericAutoInjectAttributeName = "Biwen.AutoClassGen.Attributes.AutoInjectAttribute`1";

/// <summary>
/// 非泛型AutoInjectAttribute
/// </summary>
private const string AutoInjectAttributeName = "Biwen.AutoClassGen.Attributes.AutoInjectAttribute";


#region 非泛型

//使用SyntaxProvider的ForAttributeWithMetadataName得到所有標註的服務集合
var nodesAutoInject = context.SyntaxProvider.ForAttributeWithMetadataName(
	AutoInjectAttributeName,
	(context, attributeSyntax) => true,
	(syntaxContext, _) => syntaxContext.TargetNode).Collect();

IncrementalValueProvider<(Compilation, ImmutableArray<SyntaxNode>)> compilationAndTypesInject =
	context.CompilationProvider.Combine(nodesAutoInject);

#endregion

#region 泛型

var nodesAutoInjectG = context.SyntaxProvider.ForAttributeWithMetadataName(
GenericAutoInjectAttributeName,
(context, attributeSyntax) => true,
(syntaxContext, _) => syntaxContext.TargetNode).Collect();

IncrementalValueProvider<(Compilation, ImmutableArray<SyntaxNode>)> compilationAndTypesInjectG =
	context.CompilationProvider.Combine(nodesAutoInjectG);

#endregion

//合併所有的服務的編譯類型
var join = compilationAndTypesInject.Combine(compilationAndTypesInjectG);

解下來我們定義一個Metadata類,該類主要定義Attribute的字段

private record AutoInjectDefine
{
	public string ImplType { get; set; } = null!;
	public string BaseType { get; set; } = null!;
	public string LifeTime { get; set; } = null!;
}

解析所有的標註泛型的Attribute metadata

private static List<AutoInjectDefine> GetGenericAnnotatedNodesInject(Compilation compilation, ImmutableArray<SyntaxNode> nodes)
{
	if (nodes.Length == 0) return [];
	// 註冊的服務
	List<AutoInjectDefine> autoInjects = [];
	List<string> namespaces = [];

	foreach (ClassDeclarationSyntax node in nodes.AsEnumerable().Cast<ClassDeclarationSyntax>())
	{
		AttributeSyntax? attributeSyntax = null;
		foreach (var attr in node.AttributeLists.AsEnumerable())
		{
			var attrName = attr.Attributes.FirstOrDefault()?.Name.ToString();
			attributeSyntax = attr.Attributes.First(x => x.Name.ToString().IndexOf(AttributeValueMetadataNameInject, System.StringComparison.Ordinal) == 0);

			if (attrName?.IndexOf(AttributeValueMetadataNameInject, System.StringComparison.Ordinal) == 0)
			{
				//轉譯的Entity類名
				var baseTypeName = string.Empty;

				string pattern = @"(?<=<)(?<type>\w+)(?=>)";
				var match = Regex.Match(attributeSyntax.ToString(), pattern);
				if (match.Success)
				{
					baseTypeName = match.Groups["type"].Value.Split(['.']).Last();
				}
				else
				{
					continue;
				}

				var implTypeName = node.Identifier.ValueText;
				//var rootNamespace = node.AncestorsAndSelf().OfType<NamespaceDeclarationSyntax>().Single().Name.ToString();
				var symbols = compilation.GetSymbolsWithName(implTypeName);
				foreach (ITypeSymbol symbol in symbols.Cast<ITypeSymbol>())
				{
					implTypeName = symbol.ToDisplayString();
					break;
				}

				var baseSymbols = compilation.GetSymbolsWithName(baseTypeName);
				foreach (ITypeSymbol baseSymbol in baseSymbols.Cast<ITypeSymbol>())
				{
					baseTypeName = baseSymbol.ToDisplayString();
					break;
				}

				string lifeTime = "AddScoped"; //default
				{
					if (attributeSyntax.ArgumentList != null)
					{
						for (var i = 0; i < attributeSyntax.ArgumentList!.Arguments.Count; i++)
						{
							var expressionSyntax = attributeSyntax.ArgumentList.Arguments[i].Expression;
							if (expressionSyntax.IsKind(SyntaxKind.SimpleMemberAccessExpression))
							{
								var name = (expressionSyntax as MemberAccessExpressionSyntax)!.Name.Identifier.ValueText;
								lifeTime = name switch
								{
									"Singleton" => "AddSingleton",
									"Transient" => "AddTransient",
									"Scoped" => "AddScoped",
									_ => "AddScoped",
								};
								break;
							}
						}
					}

					autoInjects.Add(new AutoInjectDefine
					{
						ImplType = implTypeName,
						BaseType = baseTypeName,
						LifeTime = lifeTime,
					});

					//命名空間
					symbols = compilation.GetSymbolsWithName(baseTypeName);
					foreach (ITypeSymbol symbol in symbols.Cast<ITypeSymbol>())
					{
						var fullNameSpace = symbol.ContainingNamespace.ToDisplayString();
						// 命名空間
						if (!namespaces.Contains(fullNameSpace))
						{
							namespaces.Add(fullNameSpace);
						}
					}
				}
			}
		}
	}

	return autoInjects;
}

解析所有標註非泛型Attribute的metadata集合


private static List<AutoInjectDefine> GetAnnotatedNodesInject(Compilation compilation, ImmutableArray<SyntaxNode> nodes)
{
	if (nodes.Length == 0) return [];
	// 註冊的服務
	List<AutoInjectDefine> autoInjects = [];
	List<string> namespaces = [];

	foreach (ClassDeclarationSyntax node in nodes.AsEnumerable().Cast<ClassDeclarationSyntax>())
	{
		AttributeSyntax? attributeSyntax = null;
		foreach (var attr in node.AttributeLists.AsEnumerable())
		{
			var attrName = attr.Attributes.FirstOrDefault()?.Name.ToString();
			attributeSyntax = attr.Attributes.FirstOrDefault(x => x.Name.ToString().IndexOf(AttributeValueMetadataNameInject, System.StringComparison.Ordinal) == 0);

			//其他的特性直接跳過
			if (attributeSyntax is null) continue;

			if (attrName?.IndexOf(AttributeValueMetadataNameInject, System.StringComparison.Ordinal) == 0)
			{
				var implTypeName = node.Identifier.ValueText;
				//var rootNamespace = node.AncestorsAndSelf().OfType<NamespaceDeclarationSyntax>().Single().Name.ToString();
				var symbols = compilation.GetSymbolsWithName(implTypeName);
				foreach (ITypeSymbol symbol in symbols.Cast<ITypeSymbol>())
				{
					implTypeName = symbol.ToDisplayString();
					break;
				}

				//轉譯的Entity類名
				var baseTypeName = string.Empty;

				if (attributeSyntax.ArgumentList == null || attributeSyntax.ArgumentList!.Arguments.Count == 0)
				{
					baseTypeName = implTypeName;
				}
				else
				{
					if (attributeSyntax.ArgumentList!.Arguments[0].Expression is TypeOfExpressionSyntax)
					{
						var eType = (attributeSyntax.ArgumentList!.Arguments[0].Expression as TypeOfExpressionSyntax)!.Type;
						if (eType.IsKind(SyntaxKind.IdentifierName))
						{
							baseTypeName = (eType as IdentifierNameSyntax)!.Identifier.ValueText;
						}
						else if (eType.IsKind(SyntaxKind.QualifiedName))
						{
							baseTypeName = (eType as QualifiedNameSyntax)!.ToString().Split(['.']).Last();
						}
						else if (eType.IsKind(SyntaxKind.AliasQualifiedName))
						{
							baseTypeName = (eType as AliasQualifiedNameSyntax)!.ToString().Split(['.']).Last();
						}
						if (string.IsNullOrEmpty(baseTypeName))
						{
							baseTypeName = implTypeName;
						}
					}
					else
					{
						baseTypeName = implTypeName;
					}
				}


				var baseSymbols = compilation.GetSymbolsWithName(baseTypeName);
				foreach (ITypeSymbol baseSymbol in baseSymbols.Cast<ITypeSymbol>())
				{
					baseTypeName = baseSymbol.ToDisplayString();
					break;
				}

				string lifeTime = "AddScoped"; //default
				{
					if (attributeSyntax.ArgumentList != null)
					{
						for (var i = 0; i < attributeSyntax.ArgumentList!.Arguments.Count; i++)
						{
							var expressionSyntax = attributeSyntax.ArgumentList.Arguments[i].Expression;
							if (expressionSyntax.IsKind(SyntaxKind.SimpleMemberAccessExpression))
							{
								var name = (expressionSyntax as MemberAccessExpressionSyntax)!.Name.Identifier.ValueText;
								lifeTime = name switch
								{
									"Singleton" => "AddSingleton",
									"Transient" => "AddTransient",
									"Scoped" => "AddScoped",
									_ => "AddScoped",
								};
								break;
							}
						}
					}

					autoInjects.Add(new AutoInjectDefine
					{
						ImplType = implTypeName,
						BaseType = baseTypeName,
						LifeTime = lifeTime,
					});

					//命名空間
					symbols = compilation.GetSymbolsWithName(baseTypeName);
					foreach (ITypeSymbol symbol in symbols.Cast<ITypeSymbol>())
					{
						var fullNameSpace = symbol.ContainingNamespace.ToDisplayString();
						// 命名空間
						if (!namespaces.Contains(fullNameSpace))
						{
							namespaces.Add(fullNameSpace);
						}
					}
				}
			}
		}
	}
	return autoInjects;
}

通過上面的兩個方法我們就取到了所有的Attribute的metadata,接下來的代碼其實就比較簡單了原理就是將metadata轉換爲形如以下的代碼:


#pragma warning disable
public static partial class AutoInjectExtension
{
    /// <summary>
    /// 自動註冊標註的服務
    /// </summary>
    /// <param name = "services"></param>
    /// <returns></returns>
    public static Microsoft.Extensions.DependencyInjection.IServiceCollection AddAutoInject(this Microsoft.Extensions.DependencyInjection.IServiceCollection services)
    {
        services.AddScoped<Biwen.AutoClassGen.TestConsole.Services.TestService2>();
        services.AddTransient<Biwen.AutoClassGen.TestConsole.Services.TestService2>();
       // ...
        return services;
    }
}
#pragma warning restore

大致的代碼如下:


context.RegisterSourceOutput(join, (ctx, nodes) =>
{
	var nodes1 = GetAnnotatedNodesInject(nodes.Left.Item1, nodes.Left.Item2);
	var nodes2 = GetGenericAnnotatedNodesInject(nodes.Right.Item1, nodes.Right.Item2);
	GenSource(ctx, [.. nodes1, .. nodes2]);
});

private static void GenSource(SourceProductionContext context, IEnumerable<AutoInjectDefine> injectDefines)
{
	// 生成代碼
	StringBuilder classes = new();
	injectDefines.Distinct().ToList().ForEach(define =>
	{
		if (define.ImplType != define.BaseType)
		{
			classes.AppendLine($@"services.{define.LifeTime}<{define.BaseType}, {define.ImplType}>();");
		}
		else
		{
			classes.AppendLine($@"services.{define.LifeTime}<{define.ImplType}>();");
		}
	});

	string rawNamespace = string.Empty;
	//_namespaces.Distinct().ToList().ForEach(ns => rawNamespace += $"using {ns};\r\n");
	var envSource = Template.Replace("$services", classes.ToString());
	envSource = envSource.Replace("$namespaces", rawNamespace);
	// format:
	envSource = FormatContent(envSource);
	context.AddSource($"Biwen.AutoClassGenInject.g.cs", SourceText.From(envSource, Encoding.UTF8));
}
/// <summary>
/// 格式化代碼
/// </summary>
/// <param name="csCode"></param>
/// <returns></returns>
private static string FormatContent(string csCode)
{
	var tree = CSharpSyntaxTree.ParseText(csCode);
	var root = tree.GetRoot().NormalizeWhitespace();
	var ret = root.ToFullString();
	return ret;
}

private const string Template = """
	// <auto-generated />
	// issue:https://github.com/vipwan/Biwen.AutoClassGen/issues
	// 如果你在使用中遇到問題,請第一時間issue,謝謝!
	// This file is generated by Biwen.AutoClassGen.AutoInjectSourceGenerator
	#pragma warning disable
	$namespaces
	public static partial class AutoInjectExtension
	{
		/// <summary>
		/// 自動註冊標註的服務
		/// </summary>
		/// <param name="services"></param>
		/// <returns></returns>
		public static  Microsoft.Extensions.DependencyInjection.IServiceCollection AddAutoInject(this Microsoft.Extensions.DependencyInjection.IServiceCollection services)
		{
			$services
			return services;
		}
	}
	
	#pragma warning restore
	""";

最終工具會自動爲你生成以下代碼:

// <auto-generated />
// issue:https://github.com/vipwan/Biwen.AutoClassGen/issues
// 如果你在使用中遇到問題,請第一時間issue,謝謝!
// This file is generated by Biwen.AutoClassGen.AutoInjectSourceGenerator
#pragma warning disable
public static partial class AutoInjectExtension
{
    /// <summary>
    /// 自動註冊標註的服務
    /// </summary>
    /// <param name = "services"></param>
    /// <returns></returns>
    public static Microsoft.Extensions.DependencyInjection.IServiceCollection AddAutoInject(this Microsoft.Extensions.DependencyInjection.IServiceCollection services)
    {
        services.AddScoped<Biwen.AutoClassGen.TestConsole.Services.TestService2>();
        services.AddTransient<Biwen.AutoClassGen.TestConsole.Services.TestService2>();
		//...
        return services;
    }
}
#pragma warning restore

以上代碼就完成了整個源生成步驟,最後你可以使用我發佈的nuget包體驗:

dotnet add package Biwen.AutoClassGen

源代碼我發佈到了GitHub,歡迎star! https://github.com/vipwan/Biwen.AutoClassGen

使用.NET源生成器(SG)實現一個自動注入的生成器

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