Add option to "reopen" closed portal session

[rfhayashi]

Adding a new parameter to portal.api/open function that accepts a portal instance. If the instance is closed, a new one with the same session id is open. If the instance is still open, the function does nothing.

This can be useful for tooling built on top of portal since it does not need to keep track whether the browser window is open or not. A use case for that is integrating portal with org babel.

TODO:

• Implement for node runtime
• Implement for web runtime
• ?Add portal parameter to api/close and api/clear functions?
• Update docs

[rfhayashi]

@djblue Opening this PR with what we discussed in slack. Will work on the TODO list after getting your initial feedback. Thanks!

[djblue]

I think the weird thing here is that if I didn't pass options initially, now I need to pass nil as the second arg for the dispatch to work correctly. I wonder if instead of arity overloading we can check if you are passing options or an exiting session? What do you think @rfhayashi?

[rfhayashi]

In my use this was not a big problem because I ended up having only one call. It does look weird though. I normally don't like testing the type of the input (unless there is clear polymorphism) because it adds complexity. But maybe in this case it is acceptable. Do you prefer that way? I'm going your direction on that one.

[djblue]

I think you can treat both arguments as maps and you would essentially be dispatching off of the existence of a :session-id. I prefer that over passing in a nil arg.

[djblue]

I think having the launcher functions take two arguments is cool, but I would rather not expose that via the api. Is that a problem for you?

[rfhayashi]

I was thinking that if one wanted to pass options they would need to pass it every time open is called, but now I see that the options get merged into an atom, so that makes sense to me now. I removed the two arguments arity from the api.

[djblue]

@rfhayashi This looks really good so far!

I think you can check the web runtime off the list as currently you can only have one session anyway.

[djblue]

@rfhayashi This PR looks like it's getting pretty close to merge. I left one additional comment and once that's resolved we should be good.

[rfhayashi]

@djblue We could potentially also add the portal parameter to close and clear, but I guess we could do that in a later PR. So I think we're good to go, but let me know if you find anything else.