I recently assembled a tool:

It’s a helper for scripting in C#. It watches a directory with C# files for changes, and whenever a file changes it gets compiled into its own executable. You can install it as an always-on service, and it comes with an opinionated set of utilities to make scripting easier.

Why?

C# the language has recently become much more succinct (top-level statements, global usings); seems like it should be good for writing fast, maintainable scripts! But the tooling around the language still isn’t quite there yet; you need a .csproj project file for every program, and dotnet run often takes a second or 2 to start up, it’s not (yet) optimized for scripting use. This proposal should help in many ways (upvote it!) but who knows if or when it will be done.

Also, this has been stuck in my head for a while:

My OS has no notion of build system. It has all the source code on it and I can edit anything and run the command again with the change immediately applied. Interpreter or compiler, I don’t know, that’s an implementation detail. Then I wake up.

Give it a spin

Instructions, source and pre-built executables for Linux+macOS+Windows are available on GitHub.

I had a weird week back in October, and it all started when I posted this GitHub issue.

What happened?

The .NET team built a feature called Hot Reload for .NET 6, which would allow for code to be changed while an application is running. It was planned as a feature for all of .NET from the start:

Our goal is to provide a consistent dev inner loop experience in .NET Core across all platforms, architectures, and workloads.

A preview version of the feature landed in April 2021 and by October it was pretty much done. I used Hot Reload throughout the preview period and loved it. Then at the last minute, Microsoft announced that the feature would be locked to Visual Studio; to say I felt disappointed would be an understatement. I posted on GitHub asking for more information, and I soon found out that many, many others felt the same way.

There was a huge community uproar, I was quoted in multiple news articles, and Microsoft eventually backed down. It was a happy ending, but I was still left with a bitter taste in my mouth.

OK, so what?

To many people, it’s not obvious why this was such a big deal. I think there are 2 main reasons:

1. Quick feedback isn’t a niche feature; it’s an essential element of any creative activity.
2. Limiting Hot Reload to Visual Studio would exacerbate .NET’s existing weaknesses.

I’ve rambled about 1 before, so I’ll focus on 2 here.

.NET’s at a bit of a disadvantage when it comes to cross-platform development, in both perception and reality. The tooling situation outside of Visual Studio (or Rider) often leaves much to be desired, and newcomers often get a poor first impression from the OmniSharp tooling in VS Code. Hot Reload in dotnet watch is a big step forward for .NET outside of Visual Studio; it’s a feature I can point to and say “yes, .NET has good tooling no matter where you use it.”

That’s the crux of the matter; removing Hot Reload from dotnet watch would harm .NET in an area it needs to do much better in. The .NET team understands this, but the change was imposed on them by senior Developer Division leadership against strong internal opposition. This suggests that senior leadership does not understand .NET (bad) or prioritizes Visual Studio over the long-term health of .NET (worse).

I like working in .NET, and the .NET team is doing a world-beating job of pushing the ecosystem forward from its stodgy enterprise-first origins. It’s unsettling that senior Developer Division leadership was willing to throw so much away to sell a few Visual Studio licenses.

Bret Victor’s talk Inventing on Principle (video, transcript) changed the way I think about computing in 2019. Inventing on Principle is partly about Bret’s guiding principle:

“Creators need an immediate connection to what they create. And what I mean by that is when you’re making something, if you make a change, or you make a decision, you need to see the effect of that immediately.”

The Edit-Compile-Run Cycle

Although Bret doesn’t use the term, programmers are deeply familiar with his principle. We’ve all worked with toolchains that introduce significant delay before you can “see” the results of a change, and we know they’re painful. Everyone wants a short edit-compile-run cycle.

But until IoP, I’d assumed that slow cycles wouldn’t materially change the output – you’d eventually get to the same place. This was wrong. I also didn’t appreciate the very small time scales involved; a 5 second delay used to seem trivial to me, but it’s still meaningfully different from a response time measured in milliseconds.

Through some very impressive custom tools, Bret shows how immediate feedback enables exploration, which then gives birth to ideas which would otherwise never see the light of day. This was an epiphany for me. Since IoP I’ve constantly been looking for better ways to code, and re-evaluating my existing processes for shorter feedback cycles. The results:

Rust

My typical Rust development workflow goes something like this:

1. Write a small function that does roughly what I want
2. Write a small unit test inline to exercise the function (even if it’s a private function)
3. Iterate using cargo test until the function is correct
4. Later, “productionize” the tests if necessary

Rust’s native support for inline unit tests helps a lot here, and the excellent type system catches a lot of issues before I even run cargo test. On the other hand, Rust’s compiler is notoriously slow and that extends to IDE tooling that depends on the Rust Language Server. I’m looking forward to Cranelift for faster debug builds.

I’ve recently been building .NET Core back-end services that run on Linux. Linux .NET development is in an interesting place; it’s clearly the future of back-end .NET, but it’s still a little rough around the edges compared to our old friend .NET-on-Windows.

Let’s dive into what you (an experienced Windows .NET developer or a .NET-curious Linux developer) need to know to start building .NET services for Linux. I’ll cover IDEs, service hosting, Linux system calls and more.

Background & Motivation

.NET development for Linux has been possible via Mono since 2004, but it was always a bit… fringe compared to Windows .NET development. That all changed when Microsoft released .NET Core in 2016 as a cross-platform .NET implementation; first-party support from Microsoft is a big deal to most .NET developers.

We’re also in a world where Linux is the lingua franca for back-end development; if you want to do anything involving cloud services, distributed systems, or containerization, Windows is typically an afterthought (if it’s supported at all). I want to skate to where the puck is going (sorry!), and it’s headed toward Linux.