MSBuild task should work on virtual projects

[jjonescz]

Summary

Using MSBuild APIs to build in-memory projects should work when targets (e.g., from .NET SDK) include <MSBuild Projects="$(MSBuildProjectFullPath)" /> (which they very often do). Currently MSBuild fails because the project file does not exist on disk. But MSBuild knows its content.

Background and Motivation

File-based apps use MSBuild APIs to build the app in memory (without a physical .csproj file). We need workarounds whenever targets use the MSBuild task against the current project, e.g., NuGet/Home#14148.

Proposed Feature

When using MSBuild APIs like

var xmlReader = XmlReader.Create(new StringReader(projectText));
var projectRoot = ProjectRootElement.Create(xmlReader);
projectRoot.FullPath = Path.Join(Environment.CurrentDirectory, "test.csproj"); // MSBuildProjectFullPath

any <MSBuild Projects="$(MSBuildProjectFullPath);..." /> should work. Notice the FullPath is set so MSBuild knows which full path corresponds to the current virtual project.

[wiktor-golonka]

@jjonescz This is exactly the problem I’ve been looking for a workaround for.
Being able to set the path for a project loaded from memory would be extremely helpful.