'MSBuildExtensionsPath' appends a '\' backslash in .NET Core mode.

[Nirmal4G]

Steps to reproduce

Set to any simple project in a directory and execute msbuild and dotnet msbuild

:: .NET Framework edition
msbuild /bl /t:Restore

:: .NET Core edition
dotnet msbuild /bl /t:Restore

Examine the .binlog file using MSBuild Structured Log Viewer.

.NET Core mode:

.NET Framework mode:

Expected behavior

MSBuildExtensionsPath should not have \ backslash at the end!

Actual behavior

MSBuildExtensionsPath has \ backslash at the end only when run in .NET Core mode!

Environment data

dotnet msbuild /version:

Microsoft (R) Build Engine version 15.5.180.51428 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

15.5.180.51428

msbuild /version:

Microsoft (R) Build Engine version 15.5.180.51428 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

15.5.180.51428

OS info:

dotnet --info

.NET Command Line Tools (2.1.4)

Product Information:
 Version:            2.1.4
 Commit SHA-1 hash:  5e8add2190

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.16299
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.1.4\

Microsoft .NET Core Shared Framework Host

  Version  : 2.0.5
  Build    : 17373eb129b3b05aa18ece963f8795d65ef8ea54

[Nirmal4G]

cc @rainersigwald According to the docs it shouldn't happen, so is it a bug on just .NET Core side?

[rainersigwald]

Can you elaborate on what problem you're observing as a result of this?

[Nirmal4G]

For my scenarios, I use custom sdks in many of my projects. When authoring some of them I found that, in the docs, MSBuildExtensionsPath should not have \ backslash at the end. So, my and possibly others' targets use it like this: $(MSBuildExtensionsPath)SomeFolder\SomeBuildProcess.targets.

When those targets gets shared, let's say, by using msbuild.exe instead of dotnet (ms)build it breaks the build process, since the path becomes like this: C:\Program Files\MSBuildSomeFolder\SomeBuildProcess.targets.

Basically, this a huge behavioral change, sure people are not directly using MSBuildExtensionsPath anymore, but I've seen code in wild, that leads to many build problems, especially for new people familiarizing with dotnet msbuild and authoring custom sdks!

[rainersigwald]

I remain confused, thanks for being patient with me.

If the spec is that it does not have a trailing slash, wouldn't you need to always call it with a slash? To use your example $(MSBuildExtensionsPath)\SomeFolder\SomeBuildProcess.targets?

[Nirmal4G]

It's because .NET Core version don't have the slash. And most people are not looking at the docs, they are learning these from the tools they installed, so if they learn from the tool (.NET Core SDK) that's displaying wrong value, instead of what's in the spec, they write incompatible code, inturn makes the build break!