Including a p5.Vector in saveJSON throws a circular structure error

[chrsmlls333]

Submitting an object with a p5.Vector object throws a TypeError. Test code and associated error:

let v = createVector(4,4);
saveJSON({ v }, 'test');

Uncaught TypeError: Converting circular structure to JSON
    --> starting at object with constructor 'p5'
    |     property '_curElement' -> object with constructor '_main.default.Renderer2D'
    --- property '_pixelsState' closes the circle
    at JSON.stringify (<anonymous>)
    at p5._main.default.saveJSON (p5.js:85038)
    at <anonymous>:1:1

I think two solutions are possible:

1. Filter out any p5 object properties transparent to the end user.

   This would involve assessing p5.Vector and any other built-in classes for error-throwing content and making a custom replacer function to replace these with simplified or string equivalents.

2. Expand the saveJSON arguments to include a user-provided replacer.

   Here is some possible code for this:

p5.prototype.saveJSON = function(json, filename, opt, replacer) {
  p5._validateParameters('saveJSON', arguments);
  let stringify;
  if (opt) {
    stringify = JSON.stringify(json, replacer);
  } else {
    stringify = JSON.stringify(json, replacer, 2);
  }
  this.saveStrings(stringify.split('\n'), filename, 'json');
};

3. Both of the above

   We could make a basic replacer and then allow a user to provide their own to either compound or override the filter.

---

Location of code edit:

p5.js/src/io/files.js

Line 1578 in cb3f597

p5.prototype.saveJSON = function(json, filename, opt) {

[chrsmlls333]

Oh, there is already a pull request to solve the vector issue specifically. #5469

Still, this may be present for other structures?

[limzykenneth]

#5469 will solve this problem for p5.Vector. Cyclic reference is still in the p5 instance itself and it will not be possible to be refactor out easily. I haven't come across anywhere else where it is a problem yet but if you find one let us know and we can look into it.

[chrsmlls333]

Would it make sense to filter out p5 instances here regardless? That could be a blanket fix for beginners' accessibility.

[limzykenneth]

What do you mean?

[limzykenneth]

Resolved by #5469