MSBuild has a grudge against $(VSToolsPath)

[jimmylewis]

Issue Description

Imports using $(VSToolsPath) are ignored by MSBuild. The preprocess step silently comments them out instead of importing the file.

Workaround: use an equivalent value ($(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion) works).

Steps to Reproduce

<Project>
  <Import Project="SDK.props" Sdk="Microsoft.NET.Sdk" />
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
  </PropertyGroup>
  <Import Project="SDK.targets" Sdk="Microsoft.NET.Sdk" />
  <Import Project="$(VSToolsPath)\TextTemplating\Microsoft.TextTemplating.targets" />
</Project>

Expected Behavior

I expect Microsoft.TextTemplating.targets to be imported.

Actual Behavior

Output from msbuild /pp:

  <!--
============================================================================================================================================
  </Import>
C:\Users\jamlew\source\repos\T4Setup\T4Setup\T4Setup.csproj
============================================================================================================================================
-->
  <!--<Import Project="$(VSToolsPath)\TextTemplating\Microsoft.TextTemplating.targets" />-->
</Project>

Analysis

Per teams chat:

[8:39 AM] Rainer Sigwald
I have no idea what's going wrong here; please file a bug. I repro but don't know what would cause a silent ignore
​[8:40 AM] Rainer Sigwald
changing $(VSToolsPath) to a constant makes it error, as I would expect
​[8:40 AM] Rainer Sigwald
ah, there's a clue
​[8:40 AM] Rainer Sigwald
we have a fallback from the early Willow days for certain folders
​[8:41 AM] Rainer Sigwald

Search paths being used for $(VSToolsPath) are ;$(MSBuildProgramFiles32)\MSBuild\Microsoft\VisualStudio\v$(VisualStudioVersion)

​[8:43 AM] Rainer Sigwald
ah, it's because there's no definition for VSToolsPath by default, but we have it in projectImportSearchPaths
​[8:43 AM] Rainer Sigwald
we should still error, though, if the fallback doesn't work
​[8:43 AM] Rainer Sigwald
so that's a bug

Versions & Configurations

C:\Program Files\Microsoft Visual Studio\2022\Preview>msbuild -version
Microsoft (R) Build Engine version 17.0.0-preview-21317-11+c579afe9c for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

17.0.0.31711

[rainersigwald]

Expounding on my IM stuff:

msbuild/src/MSBuild/app.config

Line 166 in bbeb701

<property name="VSToolsPath" value="$(MSBuildProgramFiles32)\MSBuild\Microsoft\VisualStudio\v$(VisualStudioVersion)"/>

this should be firing but is not (condition wrong?):

msbuild/src/Build/Evaluation/Evaluator.cs

Lines 1656 to 1664 in bbeb701

	// Found at least one project file for the Import, but no projects were loaded
	// atleastOneExactFilePathWasLookedAtAndNotFound would be false, eg, if the expression
	// was a wildcard and it resolved to zero files!
	if (allProjects.Count == 0 &&
	atleastOneExactFilePathWasLookedAtAndNotFound &&
	(_loadSettings & ProjectLoadSettings.IgnoreMissingImports) == 0)
	{
	ThrowForImportedProjectWithSearchPathsNotFound(fallbackSearchPathMatch, importElement);
	}

[rainersigwald]

(I accidentally posted what was meant for #6602 (comment) here, sorry.)