This PR implements a new changewave 18.0 and puts the AddSdkResolvedEnvironmentVariable functionality behind it, allowing users to disable this feature if needed.

Changes Made

1. Added Wave18_0 changewave

• Added Wave18_0 = new Version(18, 0) to ChangeWaves.cs
• Updated AllWaves array to include the new wave
• Follows the established pattern for adding new changewaves

2. Protected AddSdkResolvedEnvironmentVariable functionality

The AddSdkResolvedEnvironmentVariable method calls in Evaluator.cs are now wrapped with changewave checks:

// SDK environment variables from resolver
if (sdkResult?.EnvironmentVariablesToAdd is IDictionary<string, string> sdkEnvironmentVariablesToAdd && sdkEnvironmentVariablesToAdd.Count > 0)
{
    if (ChangeWaves.AreFeaturesEnabled(ChangeWaves.Wave18_0))
    {
        foreach (var environmentVariable in sdkEnvironmentVariablesToAdd)
        {
            _data.AddSdkResolvedEnvironmentVariable(environmentVariable.Key, environmentVariable.Value);
        }
    }
}

// DOTNET_HOST_PATH environment variable
if (File.Exists(dotnetExe))
{
    if (ChangeWaves.AreFeaturesEnabled(ChangeWaves.Wave18_0))
    {
        _data.AddSdkResolvedEnvironmentVariable("DOTNET_HOST_PATH", dotnetExe);
    }
}

3. Added comprehensive tests

• Tests verify Wave18_0 is properly included in the changewave system
• Tests confirm the feature is enabled by default (when no changewave is set)
• Tests verify the feature can be disabled by setting MSBUILDDISABLEFEATURESFROMVERSION=18.0
• Tests validate proper behavior with different changewave configurations

Usage

By default, the AddSdkResolvedEnvironmentVariable functionality remains enabled (no breaking changes).

To disable this functionality, users can set the environment variable:

MSBUILDDISABLEFEATURESFROMVERSION=18.0

This will disable Wave18_0 features and all higher-numbered waves while keeping lower-numbered wave features enabled.

Testing

All existing tests continue to pass, and new tests specifically validate:

• Wave18_0 is properly recognized as a valid changewave
• The feature works correctly when enabled
• The feature is properly disabled when Wave18_0 is disabled
• Integration with the existing changewave system

The implementation follows the established changewave pattern used throughout MSBuild for feature flags.

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.