State in the table for running kernels does not get updated

[krassowski]

The second table in the dialog does not get updated when the kernel state changes

jupyterlab-launchpad/src/dialogs.tsx

Lines 292 to 313 in 5ba3fee

	{runningKernelsItems.length > 0 ? (
	<>
	<h3 className="jp-KernelSelector-Section">
	{this.trans.__('Connect to a running kernel')}
	</h3>
	<KernelTable
	trans={this.trans}
	commands={this.commands}
	items={runningKernelsItems}
	settings={this._settings}
	query=""
	showSearchBox={false}
	onClick={item => {
	this._selection = item;
	this.options.acceptDialog();
	}}
	hideColumns={['last-used', 'star']}
	favouritesChanged={this._favoritesDatabase.changed}
	lastUsedChanged={this._lastUsedDatabase.changed}
	/>
	</>
	) : null}

Because it includes things like "state: starting" it needs to be dynamically updated. We need to trigger forceUpdate when item metadata changes, and for that we need to pass through another signal, like with lastUsedChanged:

jupyterlab-launchpad/src/components/table.tsx

Lines 103 to 117 in 5ba3fee

	// Hoisted to avoid "Rendered fewer hooks than expected" error on toggling the Star column
	const [, forceUpdate] = React.useReducer(x => x + 1, 0);
	React.useEffect(() => {
	props.favouritesChanged.connect(forceUpdate);
	return () => {
	props.favouritesChanged.disconnect(forceUpdate);
	};
	});
	React.useEffect(() => {
	props.lastUsedChanged.connect(forceUpdate);
	return () => {
	props.lastUsedChanged.disconnect(forceUpdate);
	};
	});

We derive the items from the sessions object passed in options:

jupyterlab-launchpad/src/dialogs.tsx

Line 239 in 5ba3fee

for (const model of this.options.data.sessions!) {

and we fetch the sessions when creating the dialog:

jupyterlab-launchpad/src/dialogs.tsx

Lines 75 to 80 in 5ba3fee

	body: new KernelSelector({
	data: {
	specs: sessionContext.specsManager.specs,
	sessions: sessionContext.sessionManager.running(),
	preference: sessionContext.kernelPreference
	},

The SessionManager emits runningChanged signal which we could use.

[krassowski]

SessionManager.runningChanged does not emit when minor details of the session (like kernel state) changed. We need KernelManager.runningChanged.