Improper handling of slashes in solution files

[Sumo-MBryant]

If a solution file contains a relative path to a project with a backslash (which Visual Studio and dotnet sln add both emit), and the project uses a project type GUID that is not recognised by MSBuild, any attempts to build the solution on Linux fail with the error:

{path_to_project}.metaproj : error MSB4025: The project file could not be loaded. Could not find file '{path_to_project}.metaproj'.

It appears that the code in Microsoft.Build.Construction.ProjectInSolution.CanBeMSBuildProjectFile() is failing on Linux.

Reproduction Steps:

1. Create a solution file named solution.sln with the following contents:

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio 15
VisualStudioVersion = 15.0.26403.7
MinimumVisualStudioVersion = 10.0.40219.1
Project("AAAAAAAA-1760-4266-BCC7-CA923CBCF16C") = "project", "directory\project.proj", "{1FD5F8F7-D4D3-4760-B503-03883D7CDFD7}"
EndProject
Global
	GlobalSection(SolutionConfigurationPlatforms) = preSolution
		Debug|Any CPU = Debug|Any CPU
	EndGlobalSection
	GlobalSection(ProjectConfigurationPlatforms) = postSolution
		{1FD5F8F7-D4D3-4760-B503-03883D7CDFD7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
		{1FD5F8F7-D4D3-4760-B503-03883D7CDFD7}.Debug|Any CPU.Build.0 = Debug|Any CPU
	EndGlobalSection
EndGlobal

2. Create a project file project.proj in a sub directory named directory with the following contents:

<Project>
  <PropertyGroup>
    <DefaultProjectTypeGuid>AAAAAAAA-1760-4266-BCC7-CA923CBCF16C</DefaultProjectTypeGuid>
  </PropertyGroup>

  <Target Name="Build">
    <Message Text="Build target for $(MSBuildProjectFile)" Importance="high" />
  </Target>
</Project>

3. On Linux, run dotnet msbuild solution.sln

Expected Output:

  Build target for project.proj

Actual Output:

project.proj.metaproj : error MSB4025: The project file could not be loaded. Could not find file '/homeproject.proj.metaproj'.

Workaround

Replace all backslashes in the solution file with forward slashes in the solution file.

[rainersigwald]

At a quick glance, I bet we we need a MaybeAdjustFilePath() about here.

[radical]

I get the same error on mac, with dotnet 1.0.3: dotnet build foo.sln.
But with msbuild/mono (even few months old 4.8.0) it works fine.

$ dotnet build -version
Microsoft (R) Build Engine version 15.1.1012.6693

[kellypleahy]

Seems like this would be nice to get fixed before .NET core 2.0 ships. Is that still a possibility? Who would need to be involved?

[radical]

I have mono@28dc2d4 and mono@86adc96 . I'll open a PR.

[radical]

Ah, the base patch is already in, so only the actual fix is required.

[dmitriyse]

Linux, dotnet-sdk-2.0.3
Command:

dotnet msbuild /t:MyProject:build MySolution.sln

do nothing

But on windows it works. This command builds only MyProject project from the MySolution.sln