all: improve EstimateGas API #20830
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| Original file line number | Diff line number | Diff line change |
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@@ -25,6 +25,7 @@ import ( | |
| "time" | ||
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| "github.com/ethereum/go-ethereum" | ||
| "github.com/ethereum/go-ethereum/accounts/abi" | ||
| "github.com/ethereum/go-ethereum/accounts/abi/bind" | ||
| "github.com/ethereum/go-ethereum/common" | ||
| "github.com/ethereum/go-ethereum/common/math" | ||
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@@ -49,7 +50,6 @@ var ( | |
| errBlockNumberUnsupported = errors.New("simulatedBackend cannot access blocks other than the latest block") | ||
| errBlockDoesNotExist = errors.New("block does not exist in blockchain") | ||
| errTransactionDoesNotExist = errors.New("transaction does not exist") | ||
| ) | ||
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| // SimulatedBackend implements bind.ContractBackend, simulating a blockchain in | ||
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@@ -349,8 +349,11 @@ func (b *SimulatedBackend) CallContract(ctx context.Context, call ethereum.CallM | |
| if err != nil { | ||
| return nil, err | ||
| } | ||
| res, err := b.callContract(ctx, call, b.blockchain.CurrentBlock(), state) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return res.Return(), nil | ||
| } | ||
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| // PendingCallContract executes a contract call on the pending state. | ||
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@@ -359,8 +362,11 @@ func (b *SimulatedBackend) PendingCallContract(ctx context.Context, call ethereu | |
| defer b.mu.Unlock() | ||
| defer b.pendingState.RevertToSnapshot(b.pendingState.Snapshot()) | ||
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| res, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return res.Return(), nil | ||
| } | ||
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| // PendingNonceAt implements PendingStateReader.PendingNonceAt, retrieving | ||
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@@ -398,39 +404,67 @@ func (b *SimulatedBackend) EstimateGas(ctx context.Context, call ethereum.CallMs | |
| cap = hi | ||
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| // Create a helper to check if a gas allowance results in an executable transaction | ||
| executable := func(gas uint64) (bool, *core.ExecutionResult, error) { | ||
| call.Gas = gas | ||
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| snapshot := b.pendingState.Snapshot() | ||
| res, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState) | ||
| b.pendingState.RevertToSnapshot(snapshot) | ||
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| if err != nil { | ||
| if err == core.ErrIntrinsicGas { | ||
| return true, nil, nil // Special case, raise gas limit | ||
| } | ||
| return true, nil, err // Bail out | ||
| } | ||
| return res.Failed(), res, nil | ||
| } | ||
| // Execute the binary search and hone in on an executable gas limit | ||
| for lo+1 < hi { | ||
| mid := (hi + lo) / 2 | ||
| failed, _, err := executable(mid) | ||
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| // If the error is not nil(consensus error), it means the provided message | ||
| // call or transaction will never be accepted no matter how much gas it is | ||
| // assigned. Return the error directly, don't struggle any more | ||
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There was a problem hiding this comment. This isn't strictly true. A transaction may have a line like
Member
There was a problem hiding this comment. @MicahZoltu It might help if we could collect a small pool of solidity code to add to tests and the desired behavior in those cases. Code that depends on the gas counter is a bit hard to handle correctly. e.g. ^ cannot be binary searched, so the estimator cannot ever properly pick a correct number. It might be a valid corner case though to support estimating these kinds of txs as long as they can be binary searched.
Member
There was a problem hiding this comment. Feel free to open a new issue with a code that fails estimation and we can add some tweaks. There was a problem hiding this comment. Ah sorry, I don't think I actually want support for these edge cases, it feels not worth the effort. I was merely stating that the comment in the code isn't strictly correct and for clarity to future readers it may be valuable to mention something like "we don't care about these edge cases at the moment" in the comment.
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Author
There was a problem hiding this comment. @MicahZoltu Actually the scenario you described is handled. Since all |
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| if err != nil { | ||
| return 0, err | ||
| } | ||
| if failed { | ||
| lo = mid | ||
| } else { | ||
| hi = mid | ||
| } | ||
| } | ||
| // Reject the transaction as invalid if it still fails at the highest allowance | ||
| if hi == cap { | ||
| failed, result, err := executable(hi) | ||
| if err != nil { | ||
| return 0, err | ||
| } | ||
| if failed { | ||
| if result != nil && result.Err != vm.ErrOutOfGas { | ||
| errMsg := fmt.Sprintf("always failing transaction (%v)", result.Err) | ||
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| if len(result.Revert()) > 0 { | ||
| ret, err := abi.UnpackRevert(result.Revert()) | ||
| if err != nil { | ||
| errMsg += fmt.Sprintf(" (%#x)", result.Revert()) | ||
| } else { | ||
| errMsg += fmt.Sprintf(" (%s)", ret) | ||
| } | ||
| } | ||
| return 0, errors.New(errMsg) | ||
| } | ||
| // Otherwise, the specified gas cap is too low | ||
| return 0, fmt.Errorf("gas required exceeds allowance (%d)", cap) | ||
| } | ||
| } | ||
| return hi, nil | ||
| } | ||
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| // callContract implements common code between normal and pending contract calls. | ||
| // state is modified during execution, make sure to copy it if necessary. | ||
| func (b *SimulatedBackend) callContract(ctx context.Context, call ethereum.CallMsg, block *types.Block, statedb *state.StateDB) (*core.ExecutionResult, error) { | ||
| // Ensure message is initialized properly. | ||
| if call.GasPrice == nil { | ||
| call.GasPrice = big.NewInt(1) | ||
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