Sync Calls in an Async World

[gagdiez]

In js-sdk the cross-contract calls are going to be synchronous, and I got curious on how this is implemented. Imagine I have the following situation:

1. I deploy a contract in the JS VM
2. The contract calls DEX-1 and DEX-2 to do some arbitrage, both of them live outside JS VM
3. One of the calls fails
4. If I am making synch calls, I would expect that if one fails, both are rolledback

But DEX-1 and DEX-2 live in the asynch world, how is this situation handled?.

I assume that DEX-1 and DEX-2 are executed within the JS VM node... no? So, we have a "sync" node that makes everything and then coordinates with the "async" nodes to keep states consistent?

[gagdiez]

@ailisp answered: Yes
Your contract will like this:

@call
your_method() {
  let ret1 = near.jsvmCall('DEX-1', 'method1', args1)
// ^ will throw errors if failed, lead to tx failed, and nothing will be saved to state
  if (ret1 != 'blablabla') {
    throw new Error('call in DEX-1 not   giving expect result, abort')
// ^ also lead to tx failed, and nothing will be saved to state
  }
  let ret2 = near.jsvmCall('DEX-2', 'method2', args2)
  // do something of your logic
}

@ailisp I have a follow up question: If near.jsvmCall('DEX-2', 'method2', args2) fails, then the first one is rolled back and nothing gets saved to state, right?

[ailisp]

Right. Only when entire transaction success (no error throwed), will the state change being committed to chain

[gagdiez]

and just to clarify, both contracts "DEX-1" and "DEX-2" can live outside of the node running the JS virtual machine, right?

[think-in-universe]

I think both "DEX-1" and "DEX-2" are JS contracts living in the same JSVM enclave here.

Let's consider other scenarios.

Assume I have deployed my contract X on jsvm.testnet enclave:

1. If "DEX-3" is a native NEAR contract, say Ref Finance, can we call contract methods on "DEX-3" from my contact X?
2. If "DEX-4" is a JS contract living in another JSVM (e.g. js-engine.testnet deployed by myself), can we call "DEX-4" 's functions from my contract X?

[ailisp]

Current version is, you cannot do either of them :(. This situation is same as, aurora EVM, at least as of Jan 13, 2022.

[ailisp]

and just to clarify, both contracts "DEX-1" and "DEX-2" can live outside of the node running the JS virtual machine, right?

DEX-1 and DEX-2 must be JS contract on the same jsvm.testnet enclave. Given how our node is working, the js contract lives on all nodes that have tracked the shard that jsvm.testnet lives in.