Gobie DevLog 3 - Simple C# Source Generation

In the last post about Gobie we looked at Class and Field templates along with formatting options. Today we can look at File templates.

Updates

Released in v0.4.0-alpha:

• Added file templates.

Current Status

Just to be clear, this is currently not usable for anything other than a demo. Additionally, it isn’t stable.

Demo

File templates, the ability to define that a separate file (and probably class) should be generated, is the third of four core features I wanted to include in Gobie on initial release. The usage for this pattern which is clearest to me, is to generate a dedicate log class for your existing class. Below we will look at a simple example of this pattern. In fact it is simple enough we could rely on inheritance and not generation for the bulk of the log class. In a future post we will look at a more complex example.

    [GobieGeneratorName("LoggedClass")]
    public sealed class LoggedClassGenBase : GobieClassGenerator
    {
        [GobieTemplate]
        private const string LogString = @"
            private readonly System.Collections.Generic.List<{{ClassName}}Log> logs = new();

            /// <summary> Standardized log entries for <see cref=""{{ClassName}}"">. </summary>
            public System.Collections.Generic.IEnumerable<{{ClassName}}Log> Logs => logs.AsReadOnly();";

        [GobieFileTemplate("Log")]
        private const string KeyString = @"
            using System;

            namespace {{ClassNamespace}};

            public sealed class {{ClassName}}Log
            {
                public int Id { get; set; }

                public {{ClassName}} Parent {get; set;}

                public DateTime Timestamp {get; set;}

                public string LogMessage {get; set;}
            }
            ";
    }

This is the first time we need to have multiple templates in a generator.

• GobieTemplate is defining the code we will add to the existing partial class.
• GobieFileTemplate defines a new file and new class we will generate. In the case of the Author class, this will generate an AuthorLog class.

We can apply the template as shown below.

namespace Models
{
    [LoggedClass]
    public partial class Author
    {
    }
}

And we generate the two files below:

// File: Author_LoggedClassAttribute.g.cs
namespace Models
{
    public partial class Author
    {
        private readonly System.Collections.Generic.List<AuthorLog> logs = new();
        /// <summary> Standardized log entries for <see cref = "Author">. </summary>
        public System.Collections.Generic.IEnumerable<AuthorLog> Logs => logs.AsReadOnly();
    }
}

// File: Author_LoggedClassAttribute_Log.g.cs
using System;

namespace Models;
public sealed class AuthorLog
{
    public int Id { get; set; }

    public Author Parent { get; set; }

    public DateTime Timestamp { get; set; }

    public string LogMessage { get; set; }
}

Feedback

I am very interested in feedback. Feel free to drop a note in the comments here or open an issue with your thoughts in the project repo