void

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[danfinlay]

Link to referenced issue for the lazy: #2393
And fix: #3224

[danfinlay]

The nature of the bug:

In the metamask-controller constructor, we initialize a provider, and then use that blocktracker to initialize the filter subprovider that is provided to every page:

https://github.com/lazaridiscom/metamask-extension/blob/58a554b1684fd78775b449b8f2b5d9635d30b69b/app/scripts/metamask-controller.js#L93-L94

The problem seems to be that the network controller allows this provider to be changed without notice. Sometimes it has listeners registered manually, like here:
https://github.com/lazaridiscom/metamask-extension/blob/58a554b1684fd78775b449b8f2b5d9635d30b69b/app/scripts/metamask-controller.js#L151-L153

For some reason, it seems like its old blockTracker reference was stuck on the old network, while a direct reference to the internal variable somehow was getting updated to the new network.

Frankly, this still doesn't make any sense to me at all. Just laying out some initial observations.

One post-mortem lesson I can draw is that we could isolate our network provider logic out of the metamask controller much more. This is going to become necessary soon anyway, when we allow dapps to be signed in on different blockchains, and so the sooner we isolate our instances of blockchain providers (instead of re-initializing them), the sooner we won't be prone to this kind of reference-swapping bug.