Missing default NoWarn settings when NoWarn is defined in Directory.Build.props

[rainersigwald]

From @AArnott on May 10, 2017 20:18

Building in a 15.2 VS Developer Prompt works fine, but when building in a 15.3 Preview prompt, I get lots of errors like this:

CSC : error CS1701: Assuming assembly reference 'System.Runtime, Version=4.0.20.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' used by 'System.IO' matches identity 'System.Runtime, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' of 'System.Runtime', you may need to supply runtime policy [F:\git\DevCore\src\clr\tests\TestService\TestService.csproj]
CSC : error CS1701: Assuming assembly reference 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' used by 'StreamJsonRpc' matches identity 'System.Runtime, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' of 'System.Runtime', you may need to supply runtime policy [F:\git\DevCore\src\clr\tests\TestService\TestService.csproj]
CSC : error CS1701: Assuming assembly reference 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' used by 'System.Diagnostics.TraceSource' matches identity 'System.Runtime, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' of 'System.Runtime', you may need to supply runtime policy [F:\git\DevCore\src\clr\tests\TestService\TestService.csproj]

Repro steps

git clone https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_git/DevCore
cd devcore
cd src\clr
msbuild /t:restore
msbuild

If you get other errors, you might run the "init" script in the root of the repo and try to build again.

MSBuild that is broken: 15.3.118.39484
MSBuild that works: 15.1.1012.6693

Copied from original issue: dotnet/msbuild#2088

[rainersigwald]

From @AndyGerlicher on May 10, 2017 23:4

Is this a compiler error? Or is the input somehow changing after you upgrade to 15.3?

[rainersigwald]

From @AArnott on May 11, 2017 2:28

The input is not changing. I have one enlistment and two VS command windows open. One works, one doesn't.

[rainersigwald]

From @AArnott on May 11, 2017 2:47

Good point about it being a compiler error. The differences between the compiler command line are essentially this (in addition to the different path to csc.exe):

- /nowarn:1701,1702,1705,CS1591
+ /nowarn:CS1591

CS1701 is an error in the build output, so the fact that it's no longer being suppressed seems to be what's breaking it. In fact I tried executing the exact same (broken) command line in both VS dev windows and it failed. So it appears to be a breaking change made in msbuild .targets, presumably(?) those owned by Roslyn?

UPDATED: this comment was updated with the correct diff and analysis after I realized my first diff was of the wrong command line.

[rainersigwald]

From @AArnott on May 11, 2017 2:48

This issue was moved to dotnet/roslyn#19425

[rainersigwald]

From @AArnott on May 12, 2017 15:2

Roslyn closed their issue as an msbuild or .targets change.

[rainersigwald]

@AArnott Your repro steps appear useless outside of your team; I'm getting 401 Unauthorized on https://devdiv.pkgs.visualstudio.com/DefaultCollection/_ packaging/VSIDE-RealSigned-Release/nuget/v3/index.json as a NuGet restore source.

[rainersigwald]

I have updated the title to reflect the real bug here. @AArnott has this is a Directory.Build.props:

src\Directory.Build.props:    <NoWarn Condition=" $(MSBuildProjectName.Contains('Test')) ">$(NoWarn);CS1591</NoWarn>
src\Directory.Build.props:    <NoWarn>$(NoWarn);CS1591</NoWarn>

When this intersects with

sdk/src/Tasks/Microsoft.NET.Build.Tasks/build/Microsoft.NET.Sdk.CSharp.props

Line 17 in 16b2d88

<NoWarn Condition=" '$(NoWarn)' == '' ">1701;1702;1705</NoWarn>

, it means that the default NoWarn of 1701;1702;1705 is not used, causing this error.

Note that the Directory.Build.props settings were getting overwritten before the change to the 2.0 SDK.

[AArnott]

@rainersigwald Thanks for the diagnosis. I suspect you're right.
As for my repro steps, anyone at MSFT should be able to pull packages from that feed, but only nuget.exe 4.0 (or VS) can get the access tokens necessary for it (MSBuild and dotnet cannot). Once you have pulled packages once, MSBuild and dotnet can do it after that, so long as the tokens are valid.

[nguerrera]

I'm going to close this as by-design. We deliberately changed our props to never overwrite user settings that came earlier. I think whacking user NoWarn (as before) was worse than the current behavior.

You should just add 1701;1702 to your Directory.Build.props as well when you hit this.

I have filed dotnet/roslyn#19640 in support of simply removing these (IMHO, obsolete) warnings from the compiler altogether.

I also filed #1232 to remove 1705 from our list as it;s actually an error (so NoWarn of it is useless) and perfectly valid.

If those get through, then we can remove the offending line in our default CSharp props. If not, I think we're stuck with the annoyance in this Directory.Build.props case.