src/vs/base/browser/ui/tree/objectTree.ts/CompressibleRenderer/renderElement
class CompressibleRenderer:	renderElement(node: ITreeNode<T, TFilterData>, index: number, templateData: CompressibleTemplateData<T, TFilterData, TTemplateData>, height: number | undefined): void {
		const compressedTreeNode = this.compressedTreeNodeProvider.getCompressedTreeNode(node.element) as ITreeNode<ICompressedTreeNode<T>, TFilterData>;

		if (compressedTreeNode.element.elements.length === 1) {
			templateData.compressedTreeNode = undefined;
			this.renderer.renderElement(node, index, templateData.data, height);
		} else {
			templateData.compressedTreeNode = compressedTreeNode;
			this.renderer.renderCompressedElements(compressedTreeNode, index, templateData.data, height);
		}
	}