feat(jsonrpc): implement base eth_simulateV1 JSON-RPC method#6785
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feat(jsonrpc): implement base eth_simulateV1 JSON-RPC method#6785APshenkin wants to merge 4 commits into
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What does this PR do?
Implements geth's
eth_simulateV1on java-tron's JSON-RPC surface for the MVP trading-flow use case: a single round-trip that runs N dependent calls against current head state and returns each call's effect plus synthetic transfer logs.The endpoint is opt-in via existing
eth_call-style flags; no existing behaviour changes.Why are these changes required?
This is first step to resolve #6199
Tron's JSON-RPC exposes
eth_callbut noteth_simulateV1. Two concrete consumers benefit:eth_simulateV1lets the wallet run the unsigned transaction against current head state and decode the resulting transfer logs directly into a human-readable diff.Both consumers simulate against current head state only — they don't need historical-block context or state overrides. The current implementation covers those cases end-to-end and is sufficient for what we expect to be the majority of
eth_simulateV1usage on Tron.Future work needed for the remaining use cases (debugging historical txs, what-if analysis with state overrides) requires changes in the archive node to support simulation on a specific block +
stateOverrides/blockOverrides. That's intentionally out of scope here.JSON-RPC surface
blockStateCalls: [{ calls: [...] }]. Multi-block /blockOverrides/stateOverrides→-32602.blockOverridesandstateOverridesare excluded by design — both consumers in the Motivation section simulate against current head state only, and supporting overrides would require the same archive-node plumbing called out as future work (rewinding to a specific block, applying account/storage patches before VM execution). Rejecting them with a clear error is better than silently ignoring them. Hard cap of 32 calls per block — geth's defaults (5000/block, 10000 total) are tuned for general-purpose use; our concrete cases (trading-flow approval+swap+settle, wallet preview of a single user-signed tx that fans out a few internal calls) realistically stay under ~10. Capping at 32 leaves comfortable headroom while bounding per-request memory: at ~10KB of accumulated state per call, the shared root's in-memory cache stays well under ~1MB worst-case (vs ~50MB at 5000). Anything beyond that should either be a separate request or signal misuse.blockNumOrTag: only"latest"and"pending"accepted; both resolve to the head block (Tron has instant finality — no mempool state distinct from latest).traceTransfers: truesynthesizes logs at the ERC-7528 native pseudo-address (0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE), distinguished bytopic[0]:Transfer(address,address,uint256)for native TRX moves.TRC10Transfer(address,address,uint256,uint256)for TRC-10 moves —topic[3]carriestokenIdso consumers can filter logs by asset via topics;datacarriesamount.returnFullTransactions: truereturnsblock.transactionsasTransactionResultobjects (synthetic deterministichash,gasPrice = "0x0",nonce = "0x0",v/r/szero,blockHash = keccak256("sim:" + headHash + ":1")). Defaultfalsereturns hash strings.validation: true— Tron-flavored. Geth's checks (baseFee/gasPrice/nonce) don't apply to Tron, so we pre-check per call: sender account exists and sender balance ≥callValue. Failed pre-check →status: "0x0"witherrorMessage, VM not invoked. Defaultfalsepreserves the existing constant-call permissive behaviour.Tracing
Five hook sites per transfer kind, each firing after the real balance change succeeds:
VMActuator.call()(depth 0)MUtil.transferMUtil.transferTokenVMActuator.create()(depth 0)MUtil.transferMUtil.transferTokenProgram.callToAddress(depth ≥1)addBalancepairaddTokenBalancepairProgram.callToPrecompiledAddress(depth ≥1)addTokenBalancepairProgram.suicide/suicide2MUtil.transfertransferAllTokenWithTracehelper — snapshotassetMapV2beforeMUtil.transferAllToken, emit one entry per non-zero assetDELEGATECALL/CALLCODEare explicitly skipped (no real value transfer even whensenderAddress != contextAddress).A per-frame buffer (
BufferingSimulationTracer) with a unifiedseqcounter interleaves explicitLOGopcodes with both synthetic kinds in emission order. Reverted frames drop their entries;logIndexstill increments through gaps (matches geth'slogtracer.go:128).Implementation
SimulationTracer(enterFrame/exitFrame/revertFrame/onTransfer/onTokenTransfer/onLog). Default implBufferingSimulationTracerowns the frame stack andseqcounter.VMActuatorgets opt-in setters (setInjectedRootRepository,setSimulationTracer). When the injected root is null, the existing fresh-root code path runs unchanged.Programpropagates the tracer into childPrograminstances at every sub-call origination site so nested CALL/CREATE moves are captured.Wallet.simulateConstantContractsis the new entry point. It builds the shared root + per-call child Repositories and shares the per-call execute body with the existingcallConstantContractvia a new privateexecuteOneConstantInternalhelper.SimulateV1Args,SimulateBlock(uses@JsonAnySetterto detect forward-incompatible field names),SimulateCallResult,SimulateBlockResult extends BlockResult. ReusesLogFilterElement,CallArguments,TransactionResult(additive raw-fields constructor for synthetic full-tx output).This PR has been tested by:
Unit
20 tests total:
Unit (
EthSimulateV1ArgsTest, 11 tests)-32602input-validation surface, JSON round-trip ofSimulateBlockResult, non-numerictokenIdrejection. MockedWallet, no chain context.Integration (
EthSimulateV1IntegrationTest, 9 tests,BaseTest+ LevelDB)stateSharingAcrossCalls—set(42)→get()returns 42 in one simulate; on-chain slot unchanged.revertIsolatesPerCall—set(99)→setRevert(123)→get()returns 99.validationRejectsUnactivatedSender—validation: truewith a never-seenfrom→"sender account does not exist".validationRejectsInsufficientBalance—validation: truewithvalue > balance→"insufficient balance for value".createPopulatesContractAddress— CREATE call setscontractAddressto the actual deployed address (read from the VM, not re-synthesized).returnFullTransactionsShape— verifies both response shapes, deterministic hash equality across runs.traceTrc10TopLevelCall— owner sends 50 units of token 1000001 to the pre-deployed contract; verifies all four topics + data; owner on-chain TRC-10 balance unchanged.traceTrc10MixedWithTrx— single call with bothvalue: "0x64"andtokenValue: "0x32"to an "accept-anything" sink contract; both synthetic logs emitted in TRX-first order.buffering_dropsTokenTransferOnRevertFrame— direct buffer exercise:revertFramedrops a bufferedonTokenTransfer.Manual Testing
Launched Nile testnet node with changes and run multiple commands with different setups:
Requests and Responses are long, so hide under spoiler