Honestly having .NET figure out what is needed for the image, the build context, etc. is a much better way to build and it doesn't require having the extra tooling.

Full disclosure: Engineer at Microsoft (and previously Docker) not at all involved in .NET. I work on moby (aka docker project) and internal builds of docker and CNCF related projects.

This is all it takes:

   dotnet publish -c Release

Then in Dockerfile add this:

   COPY bin/Release/net5.0/publish . 

Is that hard?

Harder than having the build toolchain produce an OCI artifact directly.

Can you explain what's "half-assed" about this solution?

Does it support docker running on MacOS M1, or Raspberry Pi? I need both of those. What about the dozens of features supported by Dockerfile? If you need even one of those features (for example, VOLUME), then you're back to writing Dockerfiles. And there's nothing wrong with writing Dockerfiles to begin with. You really don't need something coming in between, it's only going to get in the way.

> Does it support docker running on MacOS M1, or Raspberry Pi?

Not at the moment, from the article:

"We have focused on the Linux-x64 image deployment scenario for this initial release. Windows images and other architectures are key scenarios we plan to support for the full release, so watch out for new developments there."

So, ignoring that, this seems like a first cut.

The rational for this seems to be streamlining docker builds when working with dotnet:

"This Dockerfile works very well, but there are a few caveats to it that aren’t immediately apparent, which arise from the concept of a Docker build context. The build context is a the set of files that are accessible inside of a Dockerfile, and is often (though not always) the same directory as the Dockerfile. If you have a Dockerfile located beside your project file, but your project file is underneath a solution root, it’s very easy for your Docker build context to not include configuration files like Directory.Packages.props or NuGet.config that would be included in a regular dotnet build. You would have this same situation with any hierarchical configuration model, like EditorConfig or repository-local git configurations.

This mismatch between the explicitly-defined Docker build context and the .NET build process was one of the driving motivators for this feature. All of the information required to build an image is present in a standard dotnet build, we just needed to figure out the right way to represent that data in a way that container runtimes like Docker could use."

Why is this a problem in your opinion? I'm not trying to catch you out, but as someone who's not using docker for .net builds/deployments I'm trying to understand why you're dismissing this feature.

Yeah I read that paragraph and don't get what they are talking about. I don't understand what problem they are solving. I build docker images for my .NET web app multiple times a day and it works fine. You do a publish and then in Dockerfile do:

   COPY bin/Release/net5.0/publish . 

It works fine. WTF are they talking about a mismatch between explicit definition and the .NET build process?

The cynic is me would say that this is a MS attempt to take ownership and mindshare over a piece of “commodity” tooling so that devs in the ecosystem become more familiar with that than the original system, add MS/dotnet specific features and push their own system.

A modern variation of “embrace, extend, extinguish”. I doubt MS has the power or desire to extinguish containers, but getting a foot in to the deployments space would be a win for them “use dotnet because it deploys better than other solutions”.

I kinda tire of this sort of comment. I lived/worked through the EEE phase of MS back in the 90's, for good or for bad, but ultimately every large scale vendor wants to own the current "hot" space with their vendor specific tooling. No corporation is your friend.

Mainly what I was getting at here is that there are often repo-level files that are part of the .NET build process that are easy to forget to include in your build context/as part of the initial COPY command that most folks to do to a package restore before build to take advantage of Dockerfile layer caching. Right now as a user you have to be aware of the repo/file layouts and get your build contexts right if you build inside of a multi-stage Dockerfile.

IMO for a significant part of the user base there's no reason to have to manage that at all - .NET is capable of cross-targeting enough to not need to perform the build inside of a container. That keeps the user in the 'build context' that they are used to, and we can use all of that context to still end up at the ideal result - a correct container, with all of their app dependencies.

Look at the example dockerfile farther down in the article. They're performing the build inside of a dotnet sdk container then creating the application container. It sounds like you're performing the build outside of a container and just packaging the artifacts.

Right. I have Visual Studio installed. I don't need a container to build the application, I only need it for deployment.

Container to build is nice in CI pipelines, then you don't need msbuild installed on CI runners.

.net knows what version it is, it knows what deps your project has, etc. Instead of declaring this effectively twice (once for .net and once for Docker), .net is handling everything.

I also see the big call out to cases where the dockerfile and project are not in the same directory, This looks like a more straight forward improvement.

Many people want the build to be in Docker to.

I personally don't -- I publish on the host build agent and just Dockerize the publish directory

I appreciate your comments. Maybe time for me to update my docker chops and see what this brings brings to the table, if anything.