PrintMembersGenerator

A source generator that helps re-defining C# record's PrintMembers method to force include/exclude certain members.

This project is related to dotnet/csharplang#3925.

For more information about source generators, see Introducing C# source generators blog.

Overview

C# 9.0 introduced a new language feature called Records. A record is simply a reference type with some compiler-generated (synthesized) methods.

The interest of this project is on PrintMembers method, which the compiler uses when you call .ToString() on a record.

The compiler only includes all public non-override instance fields/properties in PrintMembers, and allows you to re-define PrintMembers if the provided implementation doesn't suite your need.

This source generator makes it easier to force-include or force-exclude certain record members in PrintMembers implementation through a provided attribute.

How to use

Add reference to the generator

Currently, this is not packed into a NuGet package. So you'll have to clone the source code, and add a reference to the PrintMembersSourceGenerators.csproj. The added reference should look like the following:

  <ItemGroup>
    <ProjectReference Include="PATH TO PrintMembersGenerator.csproj" 
                      OutputItemType="Analyzer"
                      ReferenceOutputAssembly="false" />
  </ItemGroup>

Use the attribute

First of all, here is the internal definition of the attribute:

namespace SourceGenerator
{
    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
    public sealed class PrintMembersAttribute : Attribute
    {
        public bool ShouldInclude { get; set; } = true;
    }
}

As you see, the attribute can only be applied to fields and properties.

• To force-include a member in PrintMembers, you should either use [PrintMembers] or [PrintMembers(ShouldInclude = true)].
• To force-exclude a member in PrintMembers, you should use [PrintMembers(ShouldInclude = false)].

Currently, positional record parameters are not supported. Support for them should be added soon through targeted attributes:

[property: PrintMembers(ShouldInclude = false)]

See this comment on dotnet/csharplang#3644.

Notes

1. If the semantics of the added attribute is the same as what the compiler does, the generator ignores the attribute.
2. The record must be partial to allow the source generator to re-define PrintMembers.