Handle null Assembly.GetEntryAssembly in ReflectionHelper.GetExecutingOrEntryAssembly

[ohadschn]

ReflectionHelper.GetExecutingOrEntryAssembly is implemented like this:

commandline/src/CommandLine/Infrastructure/ReflectionHelper.cs

Line 96 in a9243e9

return Assembly.GetEntryAssembly();

However, going by its name it should actually be implemented like this:

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

Specifically, it would solve the failure of the current implementation when called from MSTest (for background see here):

Assert.Fail failed. Exception of type System.ArgumentException thrown as expected, but the provided predicate rejected it: 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)

[moh-hassan]

The PR #430 which rebased from #387 have a correction to this problem with other approach using Assembly.GetCallingAssembly
The source code is here.

		private static Assembly GetExecutingOrEntryAssembly()
				{
					//resolve issues of null EntryAssembly in Xunit Test #392,424,389
					//return Assembly.GetEntryAssembly();
					return Assembly.GetEntryAssembly()??Assembly.GetCallingAssembly();
		}

The problem has two sides:

• The null of GetEntryAssembly in net4x in test framework(it's resolved in netcore2.x)
• The assembly attributes of Copyright, company,... may be null

This Proposal discuss the problem in detail

Currently, the Assembly.GetCallingAssembly is used in a separate class that inject it for net4x if it's null and help to resolve this problem.

The Assembly.GetCallingAssembly Method returns the Assembly of the method that invoked the currently executing method.

The GetExecutingAssembly is still used by test suit and so the assembly attributes may be null and cause the same issue.

The test framework don't modify the GetCallingAssembly .

The PR applied this solution of GetCallingAssembly and pass all unit test.

[ohadschn]

Thank you, I guess this means this issue is a duplicate - closing in favor of #403.