Consider Only Conditionally Overriding DOTNET_ROOT

[nagilson]

Description

runner-images/images/macos/assets/bashrc

Line 25 in db8d413

export DOTNET_ROOT=$HOME/.dotnet

The .bashrc configuration for the Mac OS image sets DOTNET_ROOT always. It's very common to want to use a custom .NET root folder in a private install location and to my knowledge, this runner may override the custom environment variable when tests run on the image in a pipeline.

I would advise that you conditionally set DOTNET_ROOT if and only if it is not set, at least if it is set to any non-default value for DOTNET_ROOT, such as the default system hive location on Mac OSX. Note that the system default hive location is platform specific depending upon arm64 v x64 architecture.

Platforms affected

• Azure DevOps
• GitHub Actions - Standard Runners
• GitHub Actions - Larger Runners

Runner images affected

• Ubuntu 22.04
• Ubuntu 24.04
• Ubuntu Slim
• macOS 13
• macOS 13 Arm64
• macOS 14
• macOS 14 Arm64
• macOS 15
• macOS 15 Arm64
• macOS 26 Arm64
• Windows Server 2019
• Windows Server 2022
• Windows Server 2025

Image version and build link

runner-images/images/macos/assets/bashrc

Line 25 in db8d413

export DOTNET_ROOT=$HOME/.dotnet

https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=12843965&view=logs&j=d1a37dfc-4cfe-5bcf-d646-57ef030f3cc5&t=b3bff06d-614b-5714-bf9e-b3b8549da584

Is it regression?

Not to my knowledge.

Expected behavior

Test runner respects DOTNET_ROOT custom settings.

Actual behavior

Image bashrc overrides DOTNET_ROOT.

Repro steps

Try to write a scenario that requires a custom DOTNET_ROOT folder to be set to use a private runtime not on the PATH environment variable, and run on the mac image to see whether DOTNET_ROOT is overriden when we run a program/process through the shell that required the custom DOTNET_ROOT variable.

[LittleLittleCloud]

Thanks @nagilson for reporting that issue. It's blocking C#DK intergration-testing on macos vm

In C#DK intergrating-testing, we have a list of assets that requires different .NET SDK, so we are setting different env:DOTNET_ROOT and dotnetInstallSDK path to tell C#DK to load those assets using different SDKs.

However, when vscode test instance get launched, the DOTNET_ROOT get overridden to the default %HOME%.dotnet, I think it's because when vscode instance launch, it loads bashrc somewhere to bring the environment to the default status. This prevents the intergration tests runs on the desired .NET SDKs.

The intergration tests run without problems on windows and linux because only macos sets DOTNET_ROOT, which makes me wonder what makes macos that special.

If the purpose of setting DOTNET_ROOT is simply to make dotnet cli work by default, can we mitigate that by adding the dotnet_root path to $PATH instead?

[erik-bershel]

Hello everyone!

This looks and sounds valid. Your guess regarding the nature of this difference is likely correct.
Let me check the official documentation and the proposed workaround, as well as the need to set this variable at all, and then I'll get back to you with an answer.

[LittleLittleCloud]

@erik-bershel Any update on this thread :)