Allow context key expression that compares object properties

[eamodio]

@jrieken I was attempting to change the Timeline's timeline.excludeSources setting from an array to an object (as requested here).

I've pushed a branch with the changes here: eamodio/timeline-excludesources

Here I am trying to use the timeline.excludeSources.<source-id> property as the toggled condition.

vscode/src/vs/workbench/contrib/timeline/browser/timelinePane.ts

Line 1177 in 2d551ab

toggled: ContextKeyExpr.notEquals(`config.timeline.excludeSources.${source.id}`, true)

This seems to work for the initial state, but it never gets updated when the property is removed or re-added. It looks like the cause is somewhere in here:

vscode/src/vs/platform/contextkey/browser/contextKeyService.ts

Lines 102 to 120 in db36e74

	this._listener = this._configurationService.onDidChangeConfiguration(event => {
	if (event.source === ConfigurationTarget.DEFAULT) {
	// new setting, reset everything
	const allKeys = keys(this._values);
	this._values.clear();
	emitter.fire(new ArrayContextKeyChangeEvent(allKeys));
	} else {
	const changedKeys: string[] = [];
	for (const configKey of event.affectedKeys) {
	const contextKey = `config.${configKey}`;
	if (this._values.has(contextKey)) {
	this._values.delete(contextKey);
	changedKeys.push(contextKey);
	}
	}
	emitter.fire(new ArrayContextKeyChangeEvent(changedKeys));
	}
	});
	}

Where this._values will contain timeline.excludeSources.<source-id>, but the event.affectedKeys will only have timeline.excludeSources.

/cc @rebornix

[jrieken]

but the event.affectedKeys will only have timeline.excludeSources.

That sound like an issue with the event itself, or how should this work?

[sandy081]

event.affectedKeys only contain the real configuration keys but not the full nested value tree.

[jrieken]

@eamodio this looks like a case for different printing/comparing logic. We cannot traverse into objects that have changed because this happens a lot but we can think of either a new context key operator that compare object-property values or use the regexp-operator with some JSON-based value printing (which is hopefully not huge strings...)

[eamodio]

Yeah, OK. I will leave the timeline.excludeSources as an array, but will look into adding a new context expression for object props. Thanks!