Version 2.4.x System.ArgumentNullException parsing options in unit-test

[mbedded]

Hello,

i tried all 2.4.x versions (2.4.0, 2.4.1, 2.4.2, 2.4.3) and all have the same exception. In my unit-test i call my program only with "--help" after that, i receive the following stacktrace:

// Stacktrace
System.ArgumentNullException
Value cannot be null.
Parameter name: element
   at System.Attribute.GetCustomAttributes(Assembly element, Type attributeType, Boolean inherit)
   at System.Reflection.CustomAttributeExtensions.GetCustomAttributes[T](Assembly element)
   at CommandLine.Infrastructure.ReflectionHelper.GetAttribute[TAttribute]()
   at CommandLine.Text.HelpText.AutoBuild[T](ParserResult`1 parserResult, Func`2 onError, Func`2 onExample, Boolean verbsIndex, Int32 maxDisplayWidth)
   at CommandLine.Text.HelpText.AutoBuild[T](ParserResult`1 parserResult, Int32 maxDisplayWidth)
   at CommandLine.Parser.<>c__DisplayClass17_0`1.<DisplayHelp>b__1(IEnumerable`1 _, TextWriter writer)
   at CSharpx.MaybeExtensions.Do[T1,T2](Maybe`1 maybe, Action`2 action)
   at CommandLine.ParserResultExtensions.WithNotParsed[T](ParserResult`1 result, Action`1 action)
   at CommandLine.Parser.DisplayHelp[T](ParserResult`1 parserResult, TextWriter helpWriter, Int32 maxDisplayWidth)
   at Program.<Main>d__5.MoveNext() in C:\..\..\Program.cs:line 33

My code snippets are the following ones:

// Test method (xUnit) which fails
[Fact]
public async Task CallMain_GiveHelpArgument_ExpectSuccess() {
    var result = await Program.Main(new[] { "--help" });

    Assert.Equal(ERROR_SUCCESS, result);
}

// main program
internal class Program {

  private const int ERROR_SUCCESS = 0;

  internal static async Task<int> Main(string[] args) {
      bool hasError = false;
      bool helpOrVersionRequested = false;

      ParserResult<Options> parsedOptions = Parser.Default.ParseArguments<Options>(args).WithNotParsed(errors => {
          helpOrVersionRequested = errors.Any(x => x.Tag == ErrorType.HelpRequestedError || x.Tag == ErrorType.VersionRequestedError);
          hasError = true;
      });

      if (helpOrVersionRequested) {
          return ERROR_SUCCESS;
      }

    // Execute as a normal call
    // ...
  }
  
}

// Options
internal class Options {

  [Option('c', "connectionString", Required = true, HelpText = Texts.ExplainConnection)]
  public string ConnectionString { get; set; }

  [Option('j', "jobId", Required = true, HelpText = Texts.ExplainJob)]
  public int JobId { get; set; }

  [Usage(ApplicationAlias = "Importer.exe")]
  public static IEnumerable<Example> Examples {
      get => new[] {
          new Example(Texts.ExplainExampleExecution, new Options() {
              ConnectionString="Server=MyServer;Database=MyDatabase",
              JobId = 5
          }),
      };
  }

}

I did a downgrade to version 2.3.0 without any issues. Calling the compiled Program.exe by a command line seems to be working as well. I created that test to ensure my application stops when the version or help is requested only without any additional information.

[ericnewton76]

Thats interesting... 3 levels deep into BCL reflection code.

Are you running on framework 4.7.2 or net core or what?

[ericnewton76]

So this works on my machine, running xunit.

Also I checked in your test code into branch fix/issue-389 and the build server ran the test (look for issue389_tests) https://ci.appveyor.com/project/commandlineparser/commandline/build/job/o3uhjxvn8xdha46g/tests

Not sure why you'd get this error...

[mbedded]

I am using a Console-Application with .Net Framework 4.7.2. thanks for your investigation. I will re-check this.
I am unsure, too. The only thing i did was upgrading the Nuget Package. I did it isolated (only update) and cleaned the bin + obj folder to ensure the cache is not messing up anything.

I'll can give you a feedback to this within next week.

[moh-hassan]

TL;DR,

I could reproduce the same error in a test project of target framework net472 , but sucess in netcoreapp2.1 using commaline v2.4.3.

This problem is due to the behavior of testhost in Full framework net46.x / net4.7.x and netcore2.x in reading AssemblyAttributes.

This a long story and I have previously posted an issue to vstest project to correct that behavior.

Commandlineparser consider AseemplyAttributes copyright and company shouldn't be null and raise exception (I think it should be relaxed), which may be null in hosttest and cause troubles with commandlineparser.

To workaround the problem in net472 (compliant with netstandard2)
let test classes inherit the following class:

    public class BaseTest
   {
       public BaseTest()  
      {  
	//in case multi target project,use #if because no appdomain in netcore
	#if NET472
        /* Preparing test start */  
        Assembly assembly = Assembly.GetCallingAssembly();  

        AppDomainManager manager = new AppDomainManager();  
        FieldInfo entryAssemblyfield = manager.GetType().GetField("m_entryAssembly", BindingFlags.Instance | BindingFlags.NonPublic);  
        entryAssemblyfield.SetValue(manager, assembly);  

        AppDomain domain = AppDomain.CurrentDomain;  
        FieldInfo domainManagerField = domain.GetType().GetField("_domainManager", BindingFlags.Instance | BindingFlags.NonPublic);  
        domainManagerField.SetValue(domain, manager);  
        /* Preparing test end */  
	#endif
    } 
  }

   //your test class inherit BaseTest
    public class TestProgram: BaseTest
	{
		// Test method (xUnit) which fails and really fail when inheriting the BaseTet class
		[Fact]
		public async Task CallMain_GiveHelpArgument_ExpectSuccess() {
		var result = await Program.Main(new[] { "--help" });
                    int ERROR_SUCCESS = 0;
		Assert.Equal(ERROR_SUCCESS, result);
	  }
	}	

I tested your code in multi-target project in Xunit for net472 and netcoreapp2.1 and both are sucess and NO exception is raised.
Run:

   dotnet test

The output in the multi-target test project is:

Test run for F:\github_issues\CommandParser432\CommandParser432\bin\Debug\net472\CommandParser432.dll(.NETFramework,Version=v4.7.2)
Microsoft (R) Test Execution Command Line Tool Version 15.9.0
Copyright (c) Microsoft Corporation. All rights reserved.

Starting test execution, please wait...

Total tests: 1. Passed: 1. Failed: 0. Skipped: 0.
Test Run Successful.
Test execution time: 7.9740 Seconds
Test run for F:\github_issues\CommandParser432\CommandParser432\bin\Debug\netcoreapp2.1\CommandParser432.dll(.NETCoreApp,Version=v2.1)
Microsoft (R) Test Execution Command Line Tool Version 15.9.0
Copyright (c) Microsoft Corporation. All rights reserved.

Starting test execution, please wait...

Total tests: 1. Passed: 1. Failed: 0. Skipped: 0.
Test Run Successful.
Test execution time: 5.0017 Seconds

Conclusion:

The xunit test project is working fine when you inherit the TestBase class in net472.

[JVimes]

I have the exception with NUnit. I think it's because Assembly.GetEntryAssembly() returns null on this line.

Here's a simple repro project: IssueDemo.zip (might have to build, clean, rebuild since NUnit test adapter is quirky).

[moh-hassan]

I test your demo and it fail with the error message

Error Message:
System.ArgumentNullException : Value cannot be null.
Parameter name: element

As a workaround solution, I modified your project by inheriting the class `BaseTest' that i described in my comment
and it pass successfully.

Total tests: 1. Passed: 1. Failed: 0. Skipped: 0.
Test Run Successful.

The root error is that the Assemplyattribute copyright and company are null in the hosttest of vstest which is used by NUnit and Xunit, so Commandlineparser raise an exception when execute Assembly.GetEntryAssembly() .

This bug is in net4x only. In netcoreapp2.x test pass successfully.
So it's best to test project in netcoreapp2.x which use the same packages (work only in SDK style project )

IssueDemo-sucess.zip

[MeikelLP]

I can confirm this issue using Unity 2018.3.0f1 (.NET standard 2.0).

[MeikelLP]

Issue seems to linked to Assembly.GetEntryAssembly() returning null. According to Microsoft this can only happen if any unmanaged assembly is loaded.

Some quick tests:

Debug.Log(Assembly.GetEntryAssembly()); // null
Debug.Log(Assembly.GetExecutingAssembly()); // my assembly
Debug.Log(Assembly.GetCallingAssembly()); // my assembly

I don't know too much of reflection that's why I don't know why you're using the entry assembly instead of the executing or calling one. Can you please explain?

[MeikelLP]

Probably the issue is the method GetExecutingOrEntryAssmbly which always returns the entry assembly?

commandline/src/CommandLine/Infrastructure/ReflectionHelper.cs

Lines 97 to 100 in 4bd363a

	private static Assembly GetExecutingOrEntryAssembly()
	{
	return Assembly.GetEntryAssembly();
	}

[ericnewton76]

Hmmm. Interesting. Its odd to be running commnadlineparser through unity though... I dont know much about it, but seems counterproductive since (I'm guessing) unity has its own bootloader before your library starts running? Thats the only reason I can surmise, without more information, about how GetEntryAssembly would return null.

Can you provide more info about how this is being run?

[MeikelLP]

Yes you're right unity has it's own native bootloader calling my library. This is the default unity way. I don't think there is a way around this in any way without modifying the engine itself.

I need multiple unity instances started with custom command line args each. I thought it would be wise to use a library for this purpose but it seems to conflict with unity's arguments like I mentioned in my own issue.

[JVimes]

Just a reminder this exception happens without Unity.