src/vs/workbench/contrib/files/browser/views/explorerView.ts/ExplorerView/setContextKeys
class ExplorerView:	private setContextKeys(stat: ExplorerItem | null | undefined): void {
		const folders = this.contextService.getWorkspace().folders;
		const resource = stat ? stat.resource : folders[folders.length - 1].uri;
		stat = stat || this.explorerService.findClosest(resource);
		this.resourceContext.set(resource);
		this.folderContext.set(!!stat && stat.isDirectory);
		this.readonlyContext.set(!!stat && stat.isReadonly);
		this.rootContext.set(!!stat && stat.isRoot);

		if (resource) {
			const overrides = resource ? this.editorResolverService.getEditors(resource).map(editor => editor.id) : [];
			this.availableEditorIdsContext.set(overrides.join(','));
		} else {
			this.availableEditorIdsContext.reset();
		}
	}