Skip to main content

Use the power of Source Generators with Lombok.NET

Since the introduction of source generators in .NET 5, I always wondered what the cool use cases would be that this feature makes possible. Today I want to introduce to you Lombok.NET, as an example of what Source Generators make possible.

Lombok.NET

If you are a Java developer, the name ‘Lombok’ maybe rings a bell. Lombok.NET is inspired by Project Lombok, a Java library with as main goal to help you minimize the amount of boilerplate code you need to write. I have no clue how this exactly works in Java, but Lombok.NET has the same goal using Source Generators.

Here are the list of features that Lombok.NET supports today:

Let’s have a look at 2 of them that I use the most.

Installation

Before we can use Lombok.NET, we need to install it first. this is quite easy because it is just a NuGet package:

dotnet add package Lombok.NET

Usage

Now we start using Lombok.NET. The way that it works is by annotating our classes, structs, interfaces, … with some attributes.

ToString

The first one I want to show you is the [ToString] attribute.  This will generate a ToString implementation that will print out all the private fields(can be configured) from your class.

We start with a Person class with 2 properties. Notice that I made the class partial. This is required so that Lombok.NET can extend the class definition without having to update the original file.

Now we introduce the [ToString] attribute. I set the MemberType to MemberType.Property and  AccessTypes to AccessTypes.Public because I want to include the public properties in the generated ToString implementation:

If we now build our code, a partial class is generated:

Let’s have a look at what is inside:

Nice!

Async Overloads

Let’s have a look at another example. With Async Overloads Lombok.NET will generate an async overload for every method in your interface(it also works for abstract classes and methods).

Here is an example of a small IRepository interface. Notice that here as well I need to make the interface partial:

We add an [AsyncOverloads] attribute to annotate our interface:

If we build our code, a partial interface is generated . Here is what is inside:

Certainly have a look at the other possibilities that Lombok.NET has to offer.

And if you are looking at some other use cases where Source Generators are useful, here are some examples:

Labels:

Popular posts from this blog

Podman– Command execution failed with exit code 125

After updating WSL on one of the developer machines, Podman failed to work. When we took a look through Podman Desktop, we noticed that Podman had stopped running and returned the following error message: Error: Command execution failed with exit code 125 Here are the steps we tried to fix the issue: We started by running podman info to get some extra details on what could be wrong: >podman info OS: windows/amd64 provider: wsl version: 5.3.1 Cannot connect to Podman. Please verify your connection to the Linux system using `podman system connection list`, or try `podman machine init` and `podman machine start` to manage a new Linux VM Error: unable to connect to Podman socket: failed to connect: dial tcp 127.0.0.1:2655: connectex: No connection could be made because the target machine actively refused it. That makes sense as the podman VM was not running. Let’s check the VM: >podman machine list NAME         ...
Read more

Cache stampede: when our cache turned against us

While investigating some performance issues, we ran into an ASP.NET Core API that cached a fairly expensive aggregation query for 60 seconds. Under normal load, that was fine: one request rebuilds the cache, everyone else reads from it. Under peak load, dozens of requests would arrive in that same expiry window, all see a cache miss, and all fire the same expensive query in parallel. The database didn't like that. That was the moment when our caching layer stopped helping and started hurting. A burst of requests comes in at the same time, all miss the cache, and all go hammer the database or the downstream API at once. That's a cache stampede . The cache was supposed to protect our backend, and for a few hundred milliseconds it did the opposite. Why this happens IMemoryCache.GetOrCreate (and its async sibling) looks like it protects you, but it doesn't add any locking on its own. Look at the naive version: public async Task<Report> GetReportAsync(string key) ...
Read more

A complex system designed from scratch never works

A few years ago, I worked as an architect on a big mainframe rewrite. I still count it as one of my failures. Not because the technology was wrong, but because I couldn't convince the management team to simplify the approach. Years later, the organization is still struggling to get the new system up and running. I left the project at the time, because I couldn't put my name behind an approach that would take very long and cost a lot of money without a working system to show for it along the way. Gall’s Law That memory keeps coming back to me, because it's a textbook case of Gall's Law playing out in real life. Gall's Law , from John Gall's Systemantics , states it plainly: A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works, and it cannot be patched to make it work. You have to start over with a simple system that works. What does that mean in practice,...
Read more