# Summary
Replaces the inline `errors.New("event signature mismatch")` in
generated `UnpackXxxEvent` methods with per-event package-level sentinel
errors (e.g. `ErrTransferSignatureMismatch`,
`ErrApprovalSignatureMismatch`), allowing callers to reliably
distinguish a topic mismatch from a genuine decoding failure via
`errors.Is`.
Each event gets its own sentinel, generated via the abigen template:
```go
var ErrTransferSignatureMismatch = errors.New("event signature mismatch")
```
This scoping is intentional — it allows callers to be precise about
*which* event was mismatched, which is useful when routing logs across
multiple unpackers.
# Motivation
Previously, all errors returned from `UnpackXxxEvent` were
indistinguishable without string matching. This is especially
problematic when processing logs sourced from `eth_getBlockReceipts`,
where a caller receives the full set of logs for a block across all
contracts and event types. In that context, a signature mismatch is
expected and should be skipped, while any other error (malformed data,
topic parsing failure) indicates something is genuinely wrong and should
halt execution:
```go
for _, log := range blockLogs {
event, err := contract.UnpackTransferEvent(log)
if errors.Is(err, gen.ErrTransferSignatureMismatch) {
continue // not our event, expected
}
if err != nil {
return fmt.Errorf("unexpected decode failure: %w", err) // alert
}
// process event
}
```
**Changes:**
- `abigen` template: generates a `ErrXxxSignatureMismatch` sentinel per
event and returns it on topic mismatch instead of an inline error
- Existing generated bindings & testdata: regenerated to reflect the
update
Implements #34075
Fixes race in WaitDeploy test where the backend is closed before goroutine using it wraps up.
---------
Co-authored-by: lightclient <lightclient@protonmail.com>
The root cause of the flaky test was a nonce conflict caused by async
contract deployments.
This solution defines a custom deployer with automatic nonce management.
1. Fix the error return format.
**todo**: ~~`bindtype` needs more complex logic to fix it.~~
`
if err != nil {
return nil, err
}
if err == nil {
return obj, nil
}
`
2. ~~Return pointer type object to avoid copying the whole struct
content.~~
3. Give the panic decision to the user.
4. Fix empty line at the end of function.
**TODO**: ~~fix some related test cases.~~
---------
Co-authored-by: Jared Wasinger <j-wasinger@hotmail.com>
This PR implements a new version of the abigen utility (v2) which exists
along with the pre-existing v1 version.
Abigen is a utility command provided by go-ethereum that, given a
solidity contract ABI definition, will generate Go code to transact/call
the contract methods, converting the method parameters/results and
structures defined in the contract into corresponding Go types. This is
useful for preventing the need to write custom boilerplate code for
contract interactions.
Methods in the generated bindings perform encoding between Go types and
Solidity ABI-encoded packed bytecode, as well as some action (e.g.
`eth_call` or creating and submitting a transaction). This limits the
flexibility of how the generated bindings can be used, and prevents
easily adding new functionality, as it will make the generated bindings
larger for each feature added.
Abigen v2 was conceived of by the observation that the only
functionality that generated Go bindings ought to perform is conversion
between Go types and ABI-encoded packed data. Go-ethereum already
provides various APIs which in conjunction with conversion methods
generated in v2 bindings can cover all functionality currently provided
by v1, and facilitate all other previously-desired use-cases.
## Generating Bindings
To generate contract bindings using abigen v2, invoke the `abigen`
command with the `--v2` flag. The functionality of all other flags is
preserved between the v2 and v1 versions.
## What is Generated in the Bindings
The execution of `abigen --v2` generates Go code containing methods
which convert between Go types and corresponding ABI-encoded data
expected by the contract. For each input-accepting contract method and
the constructor, a "packing" method is generated in the binding which
converts from Go types to the corresponding packed solidity expected by
the contract. If a method returns output, an "unpacking" method is
generated to convert this output from ABI-encoded data to the
corresponding Go types.
For contracts which emit events, an unpacking method is defined for each
event to unpack the corresponding raw log to the Go type that it
represents.
Likewise, where custom errors are defined by contracts, an unpack method
is generated to unpack raw error data into a Go type.
## Using the Generated Bindings
For a smooth user-experience, abigen v2 comes with a number of utility
functions to be used in conjunction with the generated bindings for
performing common contract interaction use-cases. These include:
* filtering for historical logs of a given topic
* watching the chain for emission of logs with a given topic
* contract deployment methods
* Call/Transact methods
https://geth.ethereum.org will be updated to include a new tutorial page
for abigen v2 with full code examples. The page currently exists in a
PR: https://github.com/ethereum/go-ethereum/pull/31390 .
There are also extensive examples of interactions with contract bindings
in [test
cases](cc855c7ede/accounts/abi/bind/v2/lib_test.go)
provided with this PR.
---------
Co-authored-by: Sina Mahmoodi <itz.s1na@gmail.com>
Co-authored-by: Felix Lange <fjl@twurst.com>
