src/vs/base/common/json.ts/ensurePropertyComplete
export function parseTree(text: string, errors: ParseError[] = [], options: ParseOptions = ParseOptions.DEFAULT): Node {
	let currentParent: NodeImpl = { type: 'array', offset: -1, length: -1, children: [], parent: undefined }; // artificial root

	function ensurePropertyComplete(endOffset: number) {
		if (currentParent.type === 'property') {
			currentParent.length = endOffset - currentParent.offset;
			currentParent = currentParent.parent!;
		}
	}

	function onValue(valueNode: Node): Node {
		currentParent.children!.push(valueNode);
		return valueNode;
	}

	const visitor: JSONVisitor = {
		onObjectBegin: (offset: number) => {
			currentParent = onValue({ type: 'object', offset, length: -1, parent: currentParent, children: [] });
		},
		onObjectProperty: (name: string, offset: number, length: number) => {
			currentParent = onValue({ type: 'property', offset, length: -1, parent: currentParent, children: [] });
			currentParent.children!.push({ type: 'string', value: name, offset, length, parent: currentParent });
		},
		onObjectEnd: (offset: number, length: number) => {
			currentParent.length = offset + length - currentParent.offset;
			currentParent = currentParent.parent!;
			ensurePropertyComplete(offset + length);
		},
		onArrayBegin: (offset: number, length: number) => {
			currentParent = onValue({ type: 'array', offset, length: -1, parent: currentParent, children: [] });
		},
		onArrayEnd: (offset: number, length: number) => {
			currentParent.length = offset + length - currentParent.offset;
			currentParent = currentParent.parent!;
			ensurePropertyComplete(offset + length);
		},
		onLiteralValue: (value: any, offset: number, length: number) => {
			onValue({ type: getNodeType(value), offset, length, parent: currentParent, value });
			ensurePropertyComplete(offset + length);
		},
		onSeparator: (sep: string, offset: number, length: number) => {
			if (currentParent.type === 'property') {
				if (sep === ':') {
					currentParent.colonOffset = offset;
				} else if (sep === ',') {
					ensurePropertyComplete(offset);
				}
			}
		},
		onError: (error: ParseErrorCode, offset: number, length: number) => {
			errors.push({ error, offset, length });
		}
	};
	visit(text, visitor, options);

	const result = currentParent.children![0];
	if (result) {
		delete result.parent;
	}
	return result;
}