The circular structure appears inside the parsing chart

[lagodiuk]

Error during parsing of the following grammar:

S -> A
A -> ( A ) | A A | _EPSILON_

The circular structure appears inside the parsing chart (the message from log: "earley-oop.min.js:5 Uncaught TypeError: Converting circular structure to JSON"). Despite the fact that the circular structure was detected during the log output, actually the algorithm must not produce the states with circular references (because these references are used during backtracking, for the purpose of reconstruction of the parsing forest).

Link to example: https://jsfiddle.net/2mb3w9c1/49/

However, the following grammar can be successfully parsed:

S -> A
A -> ( A ) | A A | ( )

Hence, the issue is related to handling of the epsilon transitions.