global.json not enforcing SDK version

Attempting to move dotnet/roslyn to SDK 2.0. My first step was to use global.json to enforce that 2.0 was being used to prevent bad behavior when a developer accidentally build on an environment with only 1.X installed.

I tried using global.json to achieve this by adding the following file to the root of my repo:

{
  "sdk": {
    "version": "2.0.0"
  }
}

I then built and everything succeeded. This is contrary to my expectations because I don’t have the 2.0 SDK installed on this machine. I do have dotnet on the path and MSBuild 15.3 but no 2.0 build of the SDK.

Why did this work? I really can’t understand the function of global.json if it doesn’t prevent this build from functioning.

[jaredpar]

Sounds like global.json is only useful then when:

• At least MSBuild 15.3 is installed
• dotnet 2.0.0 is installed

Lacking that it’s just a file on disk that is ignored by the build.

If that’s the case then why does our only documentation of the file display it restricting to the 1.0.0 SDK? Doesn’t seem very useful.

[nguerrera]

I believe this was covered in the documentation added for https://github.com/dotnet/docs/issues/2902