The library 'hostpolicy.dll' required to execute the application was not found in

[peterhuene]

From @sillyousu on Tuesday, 30 April 2019 02:19:35

Steps to reproduce

create a hello world project:

mkdir ClassLib
cd ClassLib
dotnet new classlib
cd ..
mkdir Main 
cd Main
dotnet new console
dotnet  add reference ..\ClassLib\ClassLib.csproj
dotnet build
dotnet .\bin\Debug\netcoreapp2.2\ClassLib.dll

.
├── ClassLib
│   ├── Class1.cs
│   └── ClassLib.csproj
└── Main
    ├── Main.csproj
    └── Program.cs

Expected behavior

meaningful error message

Actual behavior

A fatal error was encountered. The library 'hostpolicy.dll' required to execute the application was not found in 'C:\Users\supei\xd\sims\fooo\Main\bin\Debug\netcoreapp2.2\'.
Failed to run as a self-contained app. If this should be a framework-dependent app, add the C:\Users\supei\xd\sims\fooo\Main\bin\Debug\netcoreapp2.2\FooA.runtimeconfig.json file specifying the appropriate framework.

Environment data

dotnet --info output:

PS C:\Users\supei\xd\sims\fooo\Main> dotnet.exe --info
.NET Core SDK（反映任何 global.json）:
 Version:   2.2.100
 Commit:    b9f2fa0ca8

运行时环境:
 OS Name:     Windows
 OS Version:  10.0.17763
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.2.100\

Host (useful for support):
  Version: 2.2.0
  Commit:  1249f08fed

.NET Core SDKs installed:
  1.1.8 [C:\Program Files\dotnet\sdk]
  1.1.9 [C:\Program Files\dotnet\sdk]
  1.1.11 [C:\Program Files\dotnet\sdk]
  2.1.101 [C:\Program Files\dotnet\sdk]
  2.1.103 [C:\Program Files\dotnet\sdk]
  2.1.104 [C:\Program Files\dotnet\sdk]
  2.1.200 [C:\Program Files\dotnet\sdk]
  2.1.201 [C:\Program Files\dotnet\sdk]
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.300 [C:\Program Files\dotnet\sdk]
  2.1.403 [C:\Program Files\dotnet\sdk]
  2.1.500 [C:\Program Files\dotnet\sdk]
  2.1.602 [C:\Program Files\dotnet\sdk]
  2.2.100 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 1.0.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 1.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 1.0.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 1.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 1.1.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 1.1.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

Copied from original issue: dotnet/cli#11267

[peterhuene]

@sillyousu thank you for reporting this issue.

@vitek-karas is there something we could do in the host to have a more helpful error message for users when someone accidentally execs a netstandard assembly?

[vitek-karas]

This error case happens whenever we try to run any class library (not just netstandard).

• The host doesn't find .runtimeconfig.json - so it thinks it should be a self-contained app
• It doesn't find hostpolicy either - and fails

I don't think there's any specific bit of information which the host could use to determine the exact scenario. What we could do is extend the error message with something like:

A fatal error was encountered. The library 'hostpolicy.dll' required to execute the application was not found in 'C:\Users\supei\xd\sims\fooo\Main\bin\Debug\netcoreapp2.2\'.
Please make sure that `C:\Users\supei\xd\sims\fooo\Main\bin\Debug\netcoreapp2.2\ClassLib.dll` is an application. It's not possible to directly execute class libraries and other types of dependent projects.
Failed to run as a self-contained app. If this should be a framework-dependent app, add the C:\Users\supei\xd\sims\fooo\Main\bin\Debug\netcoreapp2.2\FooA.runtimeconfig.json file specifying the appropriate framework.

[borysl]

I've reproduced this issue when was running xunit tests with the project reference

[WeihanLi]

I met the error with dot net framework project

[vitek-karas]

@borysl @WeihanLi - I'm just trying to understand your comments better:

• Is it that you've ran into this by also trying to run a non-app project and are simply reporting the fact that the error message is confusing?
• Is it that you were trying to do something you think should work and it failed?

The scenario described above is supposed to fail, this issues is about the fact that the failure message is rather confusing.

[WeihanLi]

Thanks for your reply @vitek-karas , this is not exactly the same with my scene, I'm running a web project with dotnet framework, so I opened a new issue here https://github.com/dotnet/core-setup/issues/7149

[AbhishekHumagain]

Add this json to the application.runtimeconfig.json file.
{
"runtimeOptions": {
"tfm": "netcoreapp2.2",
"framework": {
"name": "Microsoft.NETCore.App",
"version": "2.0.0"
}
}
}

[WeihanLi]

I don't think that's bug or something need change, you can not run dotnet/dotnet exec with a class library, the class library had no entry point for an executable program, maybe more clearly error info

[joanna1010]

I am having the same issue when deploying my Function app in Azure.

Going into https://my-web-app.scm.azurewebsites.net
and trying to do dotnet myapp.dll
here's the output

By default, Function app boilerplate makes it as class library and you can deploy that dll straight into Azure, means it must be able to be executed properly right?

[vitek-karas]

@joanna1010 As was already mentioned above in this issue, classlib projects are not meant to be executed via dotnet project.dll. Ignoring all other problems, what method should that actually invoke in the managed code? Applications have clearly defined entry point - the Main. But classlibs don't have anything like that.

I do agree that it would be nice to provide a better error message, and we'll try to look into that.

Regarding Azure Functions - I don't know how exactly should Azure Functions be executed, but I would be very surprised if it was dotnet classlib.dll. If you're having issues running your Azure Function project, please create an issue in the respective area. I don't know for sure, but https://github.com/Azure/Azure-Functions looks promising.

[Smurf-IV]

I've reproduced this issue when was running xunit tests with the project reference

Same here via a azure-pipelines.yml file. Needing to run VSTest@2 due to needing to use rosyln against a .netcore 2.2 test dll that also performs runtime compile tests against output files.
Here is the yml extract:

- task: VSTest@2
  inputs:
    testSelector: 'testAssemblies'
    testAssemblyVer2: |
             **\*test*.dll
             !**\*TestAdapter.dll
             !**\obj\**
    runInParallel: true
    codeCoverageEnabled: true
    publishRunAttachments: true
    configuration: $(buildConfiguration)
#    runSettingsFile: 'Test.runsettings'
    testRunTitle: $(Agent.JobName)
    timeoutInMinutes: 20
    diagnosticsEnabled: true
    collectDumpOn: 'always'

I then get the following for each of the Test.dlls

##[error]Testhost process exited with error: A fatal error was encountered. The library 'hostpolicy.dll' required to execute the application was not found in 'd:\a\1\s\Tests\CSharp.Tests\bin\Release\netcoreapp2.2\'.
##[error]Failed to run as a self-contained app. If this should be a framework-dependent app, add the d:\a\1\s\Tests\CSharp.Tests\bin\Release\netcoreapp2.2\testhost.runtimeconfig.json file specifying the appropriate framework.
##[error]. Please check the diagnostic logs for more information.

But the files still run against Xunit. (See the end)
BUT, because of the errors, the VSTest action fails!

[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.4.1 (64-bit .NET Core 4.6.28008.02)
[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.4.1 (64-bit .NET Core 4.6.28008.02)
[xUnit.net 00:00:06.55]   Discovering: 2CSharp.Tests
[xUnit.net 00:00:06.64]   Discovered:  CSharp.Tests
[xUnit.net 00:00:06.65]   Starting:    CSharp.Tests
[xUnit.net 00:00:07.27]   Finished:    CSharp.Tests


  √ LaTeX2CSharp.Tests.CSharpTests.A100_SimplePower [1ms]
  √ LaTeX2CSharp.Tests.CSharpTests.A050_SimpleRoot [1ms]
  ! LaTeX2CSharp.Tests.CSharpTests.A140_NumberInVarName [1ms]
etc.

[rob83ert]

I've reproduced this issue when was running xunit tests with the project reference

Same here via a azure-pipelines.yml file. Needing to run VSTest@2 due to needing to use rosyln against a .netcore 2.2 test dll that also performs runtime compile tests against output files.
Here is the yml extract:

- task: VSTest@2
  inputs:
    testSelector: 'testAssemblies'
    testAssemblyVer2: |
             **\*test*.dll
             !**\*TestAdapter.dll
             !**\obj\**
    runInParallel: true
    codeCoverageEnabled: true
    publishRunAttachments: true
    configuration: $(buildConfiguration)
#    runSettingsFile: 'Test.runsettings'
    testRunTitle: $(Agent.JobName)
    timeoutInMinutes: 20
    diagnosticsEnabled: true
    collectDumpOn: 'always'

I then get the following for each of the Test.dlls

##[error]Testhost process exited with error: A fatal error was encountered. The library 'hostpolicy.dll' required to execute the application was not found in 'd:\a\1\s\Tests\CSharp.Tests\bin\Release\netcoreapp2.2\'.
##[error]Failed to run as a self-contained app. If this should be a framework-dependent app, add the d:\a\1\s\Tests\CSharp.Tests\bin\Release\netcoreapp2.2\testhost.runtimeconfig.json file specifying the appropriate framework.
##[error]. Please check the diagnostic logs for more information.

But the files still run against Xunit. (See the end)
BUT, because of the errors, the VSTest action fails!

[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.4.1 (64-bit .NET Core 4.6.28008.02)
[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.4.1 (64-bit .NET Core 4.6.28008.02)
[xUnit.net 00:00:06.55]   Discovering: 2CSharp.Tests
[xUnit.net 00:00:06.64]   Discovered:  CSharp.Tests
[xUnit.net 00:00:06.65]   Starting:    CSharp.Tests
[xUnit.net 00:00:07.27]   Finished:    CSharp.Tests


  √ LaTeX2CSharp.Tests.CSharpTests.A100_SimplePower [1ms]
  √ LaTeX2CSharp.Tests.CSharpTests.A050_SimpleRoot [1ms]
  ! LaTeX2CSharp.Tests.CSharpTests.A140_NumberInVarName [1ms]
etc.

I have the exact same problem...

[Smurf-IV]

@robertborr @borysl
I found the solution to "My" problem.
Notice the following line contains **\*test*.dll
This means that "Any" file that has test in the filename and is a dll will be used.

XUnit places a file called testhost.dll in the output directory, which matches the glob and is based on .netcore 1.x hence the need of the runner to attempt to use that as the runner policy for that test.dll

I changed the filer to be **\*test.dll (removed the last *) and now all is happy again; i.e. the first message is not displayed and th xunit runner still works as expected.

[Interface007]

I came to this page because of having the same message in my logs.

TLDR:
I was able to solve my problem by removing a project reference from one test-assembly to another.

Long description with a hint about searching for causes of failed builds:
Have the same issue with an in azure hosted build agent and with an on-prem build agent when running a VSTest task:

- task: VSTest@2
  inputs:
    testSelector: 'testAssemblies'
    testAssemblyVer2: |
        **\YYY.*.Tests.dll
        !**\obj\**
    searchFolder: '$(System.DefaultWorkingDirectory)'
    diagnosticsEnabled: true
    codeCoverageEnabled: true

As you can see in the task definition, it specifies to only get files matching "YYY.*.Tests.dll", which only includes my test projects.

Unfortunately, when clicking on the link of the commit hash of the "run", you see the changes of that particular commit - not the changes between ins run and the previous run. Between the last "successful run" and the first "failing run" I did several commits locally that I pushed to Azure DevOps in one single push operation.

So, the changes shown with the "failing run" may not include the cause of the failure - you have to find the changes between the two commits manually.