go-ethereum/libevm/register/register.go
Arran Schlosberg 35926db4d6
feat: temporary extras (#234)
## Why this should be merged

Registration of extras requires runtime enforcement of payload types. In
production, only a single set of types can be registered and any
attempts at re-registration will panic (by design). Although this makes
production usage safe, it doesn't allow downstream consumers (e.g. data
indexers) to use extras from different chains (e.g. `coreth` _and_
`subnet-evm`) at the same time.

## How this works

1. The `libevm/register.AtMostOnce` type can now be overridden
temporarily.
2. `params`, `core/types`, `core/vm`, and `state` packages introduce
`WithTempRegisteredExtras()` functions.
3. `libevm/temporary.WithRegisteredExtras()` provides "atomic" override
of all extras.

In all cases, the scope of the override is limited to the life of a
single function call.

## How this was tested

Relative to numbered list above:

1. Unit test of new and existing functionality.
2. Integration tests of both packages, demonstrating both payload and
behavioural override.
2025-10-02 17:42:26 +01:00

93 lines
2.7 KiB
Go

// Copyright 2024-2025 the libevm authors.
//
// The libevm additions to go-ethereum are free software: you can redistribute
// them and/or modify them under the terms of the GNU Lesser General Public License
// as published by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// The libevm additions are distributed in the hope that they will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
// General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see
// <http://www.gnu.org/licenses/>.
// Package register provides functionality for optional registration of types.
package register
import (
"errors"
"github.com/ava-labs/libevm/libevm/testonly"
)
// An AtMostOnce allows zero or one registration of a T.
type AtMostOnce[T any] struct {
v *T
}
// ErrReRegistration is returned on all but the first of calls to
// [AtMostOnce.Register].
var ErrReRegistration = errors.New("re-registration")
// Register registers `v` or returns [ErrReRegistration] if already called.
func (o *AtMostOnce[T]) Register(v T) error {
if o.Registered() {
return ErrReRegistration
}
o.v = &v
return nil
}
// MustRegister is equivalent to [AtMostOnce.Register], panicking on error.
func (o *AtMostOnce[T]) MustRegister(v T) {
if err := o.Register(v); err != nil {
panic(err)
}
}
// Registered reports whether [AtMostOnce.Register] has been called.
func (o *AtMostOnce[T]) Registered() bool {
return o.v != nil
}
// Get returns the registered value. It MUST NOT be called before
// [AtMostOnce.Register].
func (o *AtMostOnce[T]) Get() T {
return *o.v
}
// TestOnlyClear clears any previously registered value, returning `o` to its
// default state. It panics if called from a non-testing call stack.
func (o *AtMostOnce[T]) TestOnlyClear() {
testonly.OrPanic(func() {
o.v = nil
})
}
// TempOverride calls `fn`, overriding any registered `T`, but only for the life
// of the call. It is not threadsafe.
//
// It is valid to call this method with or without a prior call to
// [AtMostOnce.Register].
func (o *AtMostOnce[T]) TempOverride(with T, fn func()) {
o.temp(&with, fn)
}
// TempClear calls `fn`, clearing any registered `T`, but only for the life of
// the call. It is not threadsafe.
//
// It is valid to call this method with or without a prior call to
// [AtMostOnce.Register].
func (o *AtMostOnce[T]) TempClear(fn func()) {
o.temp(nil, fn)
}
func (o *AtMostOnce[T]) temp(with *T, fn func()) {
old := o.v
o.v = with
fn()
o.v = old
}