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[Bug] Cannot get event using event handle if nested within resource #8981

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banool opened this issue Jul 6, 2023 · 4 comments
Open

[Bug] Cannot get event using event handle if nested within resource #8981

banool opened this issue Jul 6, 2023 · 4 comments
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bug Something isn't working stale-exempt Prevents issues from being automatically marked and closed as stale

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@banool
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banool commented Jul 6, 2023

Summary

If you have an event handle and it isn't a top level field in a key struct in your Move module (aka a resource in storage) then you cannot read those events with this endpoint: https://fullnode.devnet.aptoslabs.com/v1/spec#/operations/get_events_by_event_handle.

Imagine you have this:

struct MyStruct has key {
    other: OtherStruct
}

struct OtherStruct has store {
    handle: EventHandle<Blah>
}

Neither of these work:

http://127.0.0.1:8080/v1/accounts/0x1/events/0x123::mymodule::OtherStruct/handle

http://127.0.0.1:8080/v1/accounts/0x1/events/0x123::mymodule::MyStruct/other.handle

Repro

Publish this Move module:

module addr::testing {
    use std::signer;
    use aptos_framework::event::{Self, EventHandle};
    use aptos_framework::account;

    struct MyEvent has store, drop {
        caller: address,
    }

    struct OtherStruct has store {
        handle: EventHandle<MyEvent>
    }

    struct MyStruct has key {
        other: OtherStruct
    }

    public entry fun testing(caller: &signer) acquires MyStruct {
        let caller_addr = signer::address_of(caller);
        if (!exists<MyStruct>(caller_addr)) {
            let my_struct = MyStruct {
                other: OtherStruct {
                    handle: account::new_event_handle<MyEvent>(caller),
                }
            };
            move_to(caller, my_struct);
        };

        let my_struct = borrow_global_mut<MyStruct>(caller_addr);
                
        event::emit_event(&mut my_struct.other.handle, MyEvent { caller: caller_addr });
    }
}

aptos move publish --named-addresses addr=`yq .profiles.default.account < .aptos/config.yaml` --assume-yes

Run the testing function:

aptos move run --function-id `yq .profiles.default.account < .aptos/config.yaml`::testing::testing --assume-yes

See that you can't read events:

$ curl http://127.0.0.1:8080/v1/accounts/0x`yq .profiles.default.account < .aptos/config.yaml`/events/0x`yq .profiles.default.account < .aptos/config.yaml`::testing::OtherStruct/handle
{"message":"Resource not found by Address(0x9712f422a9ed83bee4143d53e1a8598d089ca8af9c0d83248989308b80b7054e), Struct tag(0x9712f422a9ed83bee4143d53e1a8598d089ca8af9c0d83248989308b80b7054e::testing::OtherStruct) and Ledger version(397)","error_code":"resource_not_found","vm_error_code":null}

$ curl http://127.0.0.1:8080/v1/accounts/0x`yq .profiles.default.account < .aptos/config.yaml`/events/0x`yq .profiles.default.account < .aptos/config.yaml`::testing::MyStruct/other.handle
{"message":"failed to parse path `field_name`: failed to parse \"string(IdentifierWrapper)\": Invalid identifier 'other.handle'","error_code":"web_framework_error","vm_error_code":null}
@banool banool added the bug Something isn't working label Jul 6, 2023
@banool
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banool commented Jul 6, 2023

Given this hasn't been a problem until now, we can probably leave this as something @lightmark will address with v2 events.

@alnoki
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alnoki commented Jul 14, 2023

@banool @lightmark Can the solution to this issue also include lookup inside tables?

struct MyStruct has key {
    other: OtherStruct
}

struct OtherStruct has store {
    table_of_handles: Table<u64, EventHandle<Blah>>
}

Right now the only solution for this is to manually provide a view function that looks up the event handle in the table, then gets the GUID from the event handle (event::guid()), then returns the address/creation number from the GUID (guid::creator_address(), guild::creation_num()), such that the output of the view function can be fed into the event by creation number API (https://fullnode.devnet.aptoslabs.com/v1/spec#/operations/get_events_by_creation_number)

@lightmark
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@alnoki yes, imagine that is similar to solidity. Event is associated with module

@davidiw
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davidiw commented Jul 16, 2023

This was ... actually known since the beginning 😬 -- but we didn't really have any examples that needed it, so it got punted. I think we should mark this as not going to fix given the complexity in doing so and that we have a new event framework emerging shortly.

Open to hearing from others.

@sausagee sausagee added the stale-exempt Prevents issues from being automatically marked and closed as stale label Jul 21, 2023
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@davidiw @lightmark @sausagee @banool @alnoki