Make kernel connection function synchronous

[jasongrout]

Related to work in and built on top of #4697.

[jasongrout]

Rebased on master...

[jasongrout]

@blink1073 - do you remember why the kernel connectTo function returns a promise, i.e., is asynchronous?

jupyterlab/packages/services/src/kernel/default.ts

Lines 1312 to 1324 in 98d0671

	function connectTo(model: Kernel.IModel, settings?: ServerConnection.ISettings): Promise<Kernel.IKernel> {
	let serverSettings = settings || ServerConnection.makeSettings();
	let kernel = find(runningKernels, value => {
	return value.id === model.id;
	});
	if (kernel) {
	return Promise.resolve(kernel.clone());
	}
	return Promise.resolve(new DefaultKernel(
	{ name: model.name, serverSettings }, model.id
	));
	}

Just checking to make sure I'm not messing things up by not remembering why it is the way it is.

[jasongrout]

Tracing it back further, https://github.com/jupyterlab/jupyterlab/blame/09884af82886c630d0f2fa662d6f8a1525613100/packages/services/src/kernel/default.ts#L1343 indicates that we used to get the kernel model from the server if we didn't have it available locally. This was changed in the rework of services for 1.0, specifically in https://github.com/jupyterlab/jupyterlab/pull/3294/files#diff-6ce6e61bad53706cd4a7885e25ecc551R1324

It seems that now the arguments include the model, and that is all we need to create a DefaultKernel. So it does seem that the finalization of the services library was where we basically decided that connectTo did not need to be asynchronous (i.e., didn't need to query the server).

[blink1073]

That sounds right to me. I'd say leave it, not worth the major version bump.

[jasongrout]

Thanks. We're already doing a major version bump (to make the kernel message processing async and in order), so I was seeing if it was possible to fix this while we're at it.

@ian-r-rose - I think we may be able to get this into beta 3....I'll spend just a little bit more time chasing down the loose ends.

[jasongrout]

I think this may actually be good to go for beta 3.

[jasongrout]

@ian-r-rose - could you review this?

[blink1073]

I took a read-through, LGTM!

[jasongrout]

Thanks Steve!

[ian-r-rose]

I saw one problem here that was not your fault, otherwise, looks good to me!

[ian-r-rose]

I think this happened when converting the dialogs to JSX, but I saw it when testing: this JSX has commas in it that it should not have.

[ian-r-rose]

I went ahead and fixed the issue, hope you don't mind @jasongrout

[ian-r-rose]

Looks good, thanks @jasongrout!