Need a way to force delete resources

[aishairzay]

Issue To Be Solved

Resources on cadence should be deletable regardless of if they're loadable.

For example, please reference the following TX:

transaction(
) {
    prepare(acct: AuthAccount) {
      let resource <- acct.load<@AnyResource>(from: /storage/ZayTraderCollection)
      destroy resource
    }
}

You'll see i am loading in storage from ZayTraderCollection as an @AnyResource and trying to destroy it.

This TX fails like the following in TX ID run from my 0x4bcda1de73a17d95 account. flow -n mainnet transactions get d7bb1b5afec90995489a0bf0d36e1c275b546b696c2350f3fb28e0d5ed421986

❌ Transaction Error 
[Error Code: 1101] error caused by: 1 error occurred:
	* transaction invocation failed when executing transaction: [Error Code: 1101] cadence runtime error: Execution failed:
error: Checking failed:
error: mismatched types
   --> 6c4fe48768523577.SchmoesNFT:131:20

error: cannot find variable in this scope: `SchmoesNFT`
   --> 99e68982576033cf.ZayTrader:654:36

error: cannot find type in this scope: `SchmoesNFT`
   --> 99e68982576033cf.ZayTrader:655:35

error: cannot infer type parameter: `T`
   --> 99e68982576033cf.ZayTrader:655:29

error: cannot find variable in this scope: `SchmoesNFT`
   --> 99e68982576033cf.ZayTrader:870:36

error: cannot find type in this scope: `SchmoesNFT`
   --> 99e68982576033cf.ZayTrader:871:35

error: cannot infer type parameter: `T`
   --> 99e68982576033cf.ZayTrader:871:29

error: mismatched types
   --> 99e68982576033cf.ZayTrader:927:24

 --> d7bb1b5afec90995489a0bf0d36e1c275b546b696c2350f3fb28e0d5ed421986:4:6
  |
4 |       let resource <- acct.load<@AnyResource>(from: /storage/ZayTraderCollection)
  |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This error is coming because the resource that's in my account was not updated for secure cadence, and will be a lot more relevant with any future changes to cadence (stable cadence, etc)

Suggested Solution

Along with implementing try/catch as mentioned here (#1990) to help on the read side of things, we also need a way to force delete these things from a TX level to clean up an account. Either the above TX I pasted should be made to work somehow, or we need a new command for it, because in the current state, my account and others are unable to use any DAPPs that have storage iteration due to the old resource being stuck in my account.

[bjartek]

With cadence evolving and the risk of people loosing their PK this is needed so that a user can fix his storage.

[SupunS]

This was already proposed sometime back and also has the implementation: #1253
However, it was put on hold due to the feedback received. Maybe we could re-ignite the discussion.

[SupunS]

But even with that, the problem is, the destructor is forced to run whenever a resource is cleaned-up from storage, and that would need to load the resource and run a user-written code (destructor), which will run into the same problem as now.

For this particular problem to do a force clean, you would need to skip running the destructor. But that would mean we allow developers/users to destroy resources without running the destructor, which is again problematic.

[bluesign]

I think the best way would be to wrap those resources into something. LegacyResource resource, LegacyType type, etc.

[SupunS]

Another option is to make the storage interaction functions handle errors gracefully. i.e: not to panic, but rather return nil if something goes wrong.
(Or provide a global way of handling errors gracefully like in #1990)

[bjartek]

The underlying problem is with those iterators so that could work.

[bjartek]

I think this can be closed now as #2200 removed the core need for it?

[j1010001]

this needs a wider discussion to determine if we want to have this functionality (Cadence LDM) - it has protocol/product implications.