Static graph construction does not use a shared evaluation context

[rainersigwald]

With a tiny API consumer project (reference Microsoft.Build.MSBuildLocator and Microsoft.Build:

using Microsoft.Build.Graph;
using Microsoft.Build.Locator;

namespace GraphBuilderApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
            MSBuildLocator.RegisterDefaults();
            DoMSBuildStuff();
        }

        private static void DoMSBuildStuff()
        {
            ProjectGraph graph = new ProjectGraph(@"C:\src\msbuild\MSBuild.sln");

            System.Console.WriteLine($"Projects in the solution: {graph.ProjectNodes.Count}");
        }
    }
}

Run under tracing and look at events like Microsoft-Build/SdkResolverServiceFindResolversManifests/Stop and Microsoft-Build/SdkResolverResolveSdk/Stop. In my test run (on the MSBuild repo), I see a lot of wasted work:

Event	Count	Total time
FindResolversManifests	84	597ms
SdkResolverResolveSdk	314	17,328ms

Debugging through, each project evaluated by the graph is in its own EvaluationContext, so they share nothing--including the list of resolvers.

[AndyGerlicher]

Just to add some info here. Here is my before/after fixing this on the client side.

With EvaluationContext.SharingPolicy.Shared:

Static graph loaded in 5.975 seconds: 811 nodes, 4299 edges

With default (EvaluationContext.SharingPolicy.Isolated):

Static graph loaded in 10.701 seconds: 811 nodes, 4299 edges

This is pretty significant! Definitely worth updating the default.