Refactor NetGraphItem

[jgosmann]

At the moment all items in the net graph are implemented in the same NetGraphItem class which results in a lot if-clauses in various places of the class. Usually this is an indication that polymorphism should be used. Not sure, if there are any JS limitations preventing this, but it seems that NetGraphItem should be refactored (though maybe not before the summer school).

[tcstewar]

I definitely agree, although probably for after the summer school. When I wrote it I wasn't sure what polymorphism would be needed, but I think we have a pretty good sense of it now. No JS limitations on this that I know of (we're already using subclassing for Components, so the same approach should work).

I will note that there is a little bit of duck-typing happening with the NetGraphConnections, as I think there are one or two places where I take advantage of the fact that both NetGraphConnections and NetGraphItems have some methods in common (remove is the one that's coming to mind). So that might also get cleaned up in this.

[jgosmann]

Do we really want this for the 0.2 release? It wouldn't involve any user-facing changes, so it could wait after the release. Though, I would target 0.3 for the refactoring latest as I believe code quality to be important.

It would also be helpful to have the unit testing infrastructure in place for such major changes.
@Seanny123 What's the state on that? Is there a PR/branch to play around with?

[Seanny123]

There's a branch for unit tests, but its state is basically unusable and so it only resides on my desktop in the lab. Rest assured it's my first priority after I finish my spa-similarity plots and branch, which I'm 50% done.

[tcstewar]

Do we really want this for the 0.2 release? It wouldn't involve any user-facing changes, so it could wait after the release. Though, I would target 0.3 for the refactoring latest as I believe code quality to be important.

Agreed. I think we can put it off till 0.3 (but no later).

[Seanny123]

Now that we have some unit tests, what's left in this refactoring?

[tcstewar]

Now that we have some unit tests, what's left in this refactoring?

What's left here would be the actual refactoring. And making sure that the tests actually test something that could be broken by the refactoring. (Right now we don't really have unit tests -- we have tests that test the overall functionality, rather than individual small units).