Not intuitive error message when missing argument (i.e. dotnet sln)

[krwq]

Steps to reproduce

• dotnet sln

Expected behavior

• show help, list of commands, some actionable error

Actual behavior

Required command was not provided.

Environment data

dotnet --info output:

.NET Command Line Tools (2.0.0-alpha-alpha-004933)

Product Information:
 Version:            2.0.0-alpha-alpha-004933
 Commit SHA-1 hash:  30d281bc4c

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.14393
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   D:\cli\artifacts\win10-x64\stage2\sdk\2.0.0-alpha-004936\

[mikkelbu]

I think that this issue is the same as #7559 (note that the Steps to reproduce is wrong as it is copy-paste from #7558) which I've tried to solve in dotnet/cli#6506

[krwq]

@livarcocc @jonsequitur is this still an issue with new parser?

[jonsequitur]

@krwq This behavior is unchanged from V1 to V2 so not related to the new parser. We've been applying the parser label to issues that we can resolve using the new parser and this one is a candidate.

[mikkelbu]

@krwq dotnet/cli#6506 got merged into master, so now dotnet sln should give you "Required command was not provided" followed by the help file for the sln command.

[livarcocc]

Closing since we display help now in this situation.