C#增量源代码生成器未运行，请求排查问题

我想要创建一个增量源代码生成器，用于读取JSON文件并生成对应的类。但构建解决方案时没有生成任何文件，甚至生成器中的调试语句也未触发。

生成器项目配置 #

<PropertyGroup>
  <TargetFramework>netstandard2.0</TargetFramework>
  <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
  <IsRoslynComponent>true</IsRoslynComponent>
  <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
  <CompilerGeneratedFilesOutputPath>Generated</CompilerGeneratedFilesOutputPath>
</PropertyGroup>

<ItemGroup>
  <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4">
    <PrivateAssets>all</PrivateAssets>
    <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
  </PackageReference>
  <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.5.0" PrivateAssets="all" />
  <PackageReference Include="Newtonsoft.Json" Version="13.0.2" />
</ItemGroup>

<ItemGroup>
  <None Include="$(OutputPath)\$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
</ItemGroup>

应用项目引用方式 #

<ItemGroup>
  <ProjectReference Include="..\SourceGenerators\SourceGenerators.csproj"
    OutputItemType="Analyzer"
    ReferenceOutputAssembly="false" />
</ItemGroup>

生成器代码 #

[Generator]
public class MetricsSourceGenerator : IIncrementalGenerator
{
    public void Initialize(IncrementalGeneratorInitializationContext initContext)
    {
        System.Diagnostics.Debugger.Launch();

        var textFile = initContext.AdditionalTextsProvider.Where(file => file.Path.Contains("Potato"));

        var contentProvider = textFile.Select((text, cancellationToken) => text.GetText(cancellationToken).ToString());

        initContext.RegisterSourceOutput(contentProvider, (sourceProductionContext, fileContents) =>
        {
            var metricDefinitions = JsonConvert.DeserializeObject<MetricDefinitions>(fileContents);

            foreach (var metric in metricDefinitions.Metrics)
            {
                var source = GenerateClassSourceCode(metric);

                sourceProductionContext.AddSource(metric.Name + "AnalyticsCounter.cs", SourceText.From(source, Encoding.UTF8));
            }
        });
    }

    private string GenerateClassSourceCode(MetricDefinition metric)
    {
        var className = metric.Name + "AnalyticsCounter";

        var dimensionsOwnParameters = string.Join(", ", metric.Dimensions.Select(dimensionName => $"string {dimensionName}"));

        var dimensionsTrackValueParameters = string.Join(", ", metric.Dimensions);

        return $@"
// <auto-generated/>
using System.Collections.Generic;
using Microsoft.ApplicationInsights;

/*
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This class is auto-generated by {this.GetType().Name}.
Please DO NOT modify it manually!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
namespace App.DataLayer.Analytics.Metrics
{{
    public class {className} : AnalyticsCounter
    {{
        public {className}(TelemetryClient telemetryClient)
            : base(""{metric.Name}"", telemetryClient)
        {{
        }}

        public void Increment({dimensionsOwnParameters})
        {{
            Metric.TrackValue(1, {dimensionsTrackValueParameters});
        }}
    }}
}}
";
    }
}

public class MetricDefinitions
{
    public MetricDefinition[] Metrics { get; set; }
}

public class MetricDefinition
{
    public string Name { get; set; }

    public bool IsSimpleCounter { get; set; }

    public string[] Dimensions { get; set; }
}

请问我哪里操作有误？是否需要采用其他构建方式？

1. JSON文件未标记为AdditionalText #

生成器依赖AdditionalTextsProvider获取文件，若目标JSON文件未被识别为AdditionalText，生成器不会触发。需在应用项目中将JSON文件的BuildAction设置为AdditionalFiles：

<ItemGroup>
  <AdditionalFiles Include="**/Potato*.json" />
</ItemGroup>

确保文件路径包含"Potato"，匹配代码中的过滤条件file.Path.Contains("Potato")。

2. 生成器项目依赖配置问题 #

• 增量生成器无需引用Microsoft.CodeAnalysis.CSharp.Workspaces，替换为轻量化的Microsoft.CodeAnalysis.CSharp包：

  <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.5.0" PrivateAssets="all" />
  

• Newtonsoft.Json未设置PrivateAssets="all"，可能引发依赖冲突，修改为：

  <PackageReference Include="Newtonsoft.Json" Version="13.0.2" PrivateAssets="all" />
  

3. 调试语句的局限性 #

System.Diagnostics.Debugger.Launch()在常规编译环境中可能无法触发（生成器运行在编译进程内），改用诊断输出验证生成器是否启动：

initContext.ReportDiagnostic(Diagnostic.Create(
    new DiagnosticDescriptor("GEN001", "Generator Started", "Metrics生成器已初始化", "Generator", DiagnosticSeverity.Info, true),
    Location.None));

可在VS的「错误列表」中查看该诊断信息。

4. 生成代码的语法错误 #

生成的构造函数代码存在双引号转义错误：base(""{metric.Name}"", telemetryClient)会生成无效的字符串格式，修改为：

base($"{metric.Name}", telemetryClient)

语法错误会导致生成的代码无法编译，VS会自动隐藏错误的生成文件，因此你看不到输出结果。

5. 构建缓存与路径问题 #

• 清理解决方案，删除bin、obj文件夹后重新构建，避免旧缓存干扰。
• CompilerGeneratedFilesOutputPath默认在生成器项目目录下，若需在应用项目中查看生成文件，需在应用项目的PropertyGroup中添加：

  <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
  

6. 增量生成器逻辑的健壮性优化 #

添加空值检查，避免空引用异常导致生成器崩溃：

var contentProvider = textFile.Select((text, cancellationToken) => 
{
    var textContent = text.GetText(cancellationToken);
    return textContent?.ToString() ?? string.Empty;
});

同时在反序列化后检查metricDefinitions和metricDefinitions.Metrics是否为空：

if (metricDefinitions?.Metrics == null) return;

内容的提问来源于stack exchange，提问作者Michael Tontchev