Clear Pull Request Form when canceled or completed.

[paladique]

Fixes #479

Instead subscribing to the cancel and completion actions of the PullRequestCreation view model, ResetViewModel() was added to IViewModel that will execute the VMs overridden BaseViewModel's Reset(),

[paladique]

I had to the option to remove or hide this with new, I decided to remove it since this was not in use anywhere,

[shana]

Indentation is weird here.

[shana]

So to avoid adding the Reset method to the GitHubPaneViewModel, which doesn't need it, an more interesting implementation can be:

• Add a new interface called IResettable and move the Reset method definition in it
• Add the new interface to the list of interfaces that the PullRequestCreationViewModel implements
• In the UIController reset method, check whether the view model is an IResettable and only call the method if it is.

[paladique]

This seems like a handy C# 6 thing! What I'm doing here is using the null conditional operator to speculate that the VM could be a member of IResettable and to access Reset() if it is, so if vm is null, and the operator avoids a null reference exception

[shana]

Yup, this is a very handy thing indeed!

[shana]

@paladique I forget, did we figure out why these tests fail in CI? Do they pass in Visual Studio?

[paladique]

@shana ran the tests in VS and it's failing on the new test added for the Reset() method, ResetIsCalled(). Clearing the form is successful when doing it in the UI, but in the test vm?.Reset() is skipped because the PullRequestCreationProxy is not being recognized as a member of IResettable

Should I be mocking IResettable in some way? That seems unnecessary because PullRequestCreation is already a member. This must be missing something else.

[shana]

Oh! Yes, you need to mark the viewmodel as IResettable so it's recognized as such. We already do that for some views here: https://github.com/github/VisualStudio/blob/master/src/UnitTests/GitHub.App/Controllers/UIControllerTests.cs#L44-L47

You need to do it for the viewmodel in the SetupViewModel method.

[paladique]

This was mostly an exploratory PR, so closing for now!