Staged contract update

[turbolent]

Issue To Be Solved

Stable Cadence will introduce several breaking changes, which will get introduced in a spork.

We should aim to provide tooling to make the upgrade process as smooth as possible for developers.

Suggested Solution

• As Stable Cadence will get enabled during a spork, contracts can only be, and also have to be, deployed right after the spork is complete – as long as the contract is not updated, it might be unusable. This makes the update very time-critical. We could give developers means to schedule an update, i.e. update a contract for a “future” release, so that when the network got sporked, the contract update is automatically performed.

[dreamsmasher]

would this be a good case for implementing versioned contracts? rather than giving developers a hard deadline of "update by the spork or you're borked", we could allow contracts to specify minimum cadence versions?

[turbolent]

It would indeed be great to support multiple versions of Cadence at the same time. We have investigated and evaluated this in the past, and it is unclear how this could be achieved, as well as how much effort it would be to implement such functionality.

Instead, we are hoping to arrive at a long-term supported version of Cadence sooner than later, which obsoletes having to support multiple versions.

[j1010001]

draft: https://www.notion.so/dapperlabs/Cadence-Contract-Updates-Design-Doc-02ab771937e74bd1a09471334a64ece4

[j1010001]

Notes from Meeting @sisyphusSmiling and @joshuahannan today.

• Gio has a draft POC implementation: https://github.com/sisyphusSmiling/contract-updater/blob/main/contracts/ContractUpdater.cdc
• If a contract update fails it will panic, so we will need to run a Tx after spork per contract to make sure the different contract updates are independent on each other.
  Next steps:
  [] @sisyphusSmiling will update to stable Cadence runtime when we have a pre-release and test.
  [] @sisyphusSmiling Publish FLIP by end of Aug.

[turbolent]

Depends on #2700

[sisyphusSmiling]

Just proposed in related FLIP

[j1010001]

implementation: https://github.com/sisyphusSmiling/contract-updater

[j1010001]

completed and deployed to testnet: https://github.com/onflow/contract-updater