zepumph
commented
2 years ago Great catch @marlitas! Let me do some explaining.
Tandems are already set up to be "monolithic" in the sense that only one instance of Tandem should exist for a given phetioID. Thus, if you createTandem to make something that already exists, createTandem() will just return that instance instead of creating a duplicate instance. See here:
For dynamic elements, we do the same logic, where we re-use tandems if available (most often they aren't though, like you in your case where they have already been disposed, but we'll get to that):
So much of my investigation here was confirming that DynamicTandems are supported in that same way, and shouldn't just be re-created each time a new element is made. The same goes for disposal. We don't necessarily need to dispose it manually for dynamic elements, because it should be disposed automatically if it has no more children etc. The issue was that when disposing the child, we were cutting the parent off from the child, but not the child from the parent. Thus the child, though disposed, still had a reference to the parent, and thus wouldn't get garbage collected. I believe this solves you leak. Please review.
marlitas
While working on Mean: Share and Balance @samreid and I noticed a memory leak that involved tandem and dynamicTandem.
To recreate:
Upon further investigation we added
element.tandem.dispose();toPhetioDynamicElementContainer.tsline 355 ( inside disposeElement function). This eliminated the tandem leak.Before fully implementing this change we wanted to check with @zepumph to make sure this wouldn't waterfall into affecting other phetio functionality negatively.