rpc: impl eth fill transaction

[lupin012]

closes #21864

Implements eth_fillTransaction compatible with Geth.

The method accepts the parameters of a partial transaction, fills in the missing fields (nonce, gas limit, gas price / EIP-1559 fee caps, chain ID, blob fee), and returns the RLP-serialized transaction (raw) together with its JSON representation (tx), without signing or submitting it.

Main changes

• rpc/jsonrpc/eth_fill_transaction.go — implementation of FillTransaction on APIImpl, with a fillFeeDefaults helper that handles both the pre-London path (gas price from oracle) and the post-London path (EIP-1559, blob fee).
• rpc/ethapi/api.go — adds SignTransactionResult (reusable by eth_signTransaction as well) with a custom MarshalJSON that strips block-placement/sender fields and normalises fee and signature fields to match Geth's output.
• rpc/jsonrpc/eth_api.go — adds FillTransaction to the EthAPI interface.
• rpc/jsonrpc/eth_fill_transaction_test.go and rpc/ethapi/api_test.go — tests covering the happy path, conflicting fee arguments, wrong chainID, contract creation without data, blob transactions before Cancun, and JSON serialisation for both EIP-1559 and legacy transactions.
• cmd/rpcdaemon/README.md — marks eth_fillTransaction as implemented.

Notes

• The rpc-tests version will be tagged and rpc_version.env updated to a stable tag once the PR is approved
• Added 15 RPC tests to latest, comparing them against the Geth response.

[Copilot]

Pull request overview

Implements the eth_fillTransaction JSON-RPC method in rpcdaemon, returning an unsigned, default-populated transaction along with its raw-encoded form (Geth-compatible response shape).

Changes:

• Add eth_fillTransaction implementation that fills nonce/fees/gas/chainId defaults and returns an RLP/binary-encoded transaction plus its JSON form.
• Introduce ethapi.SignTransactionResult with custom JSON marshaling to match Geth’s field behavior for unsigned txs.
• Update docs and CI rpc-tests version pinning to reflect the new method support.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
rpc/jsonrpc/eth_fill_transaction.go	Adds the FillTransaction RPC implementation and fee-default helper logic.
rpc/jsonrpc/eth_fill_transaction_test.go	Adds basic unit tests for default filling and a few validation errors.
rpc/jsonrpc/eth_api.go	Extends the EthAPI interface to include FillTransaction.
rpc/ethapi/api.go	Adds SignTransactionResult + custom MarshalJSON to normalize response fields for fill/sign flows.
rpc/ethapi/api_test.go	Adds tests covering SignTransactionResult JSON normalization for legacy and EIP-1559 txs.
cmd/rpcdaemon/README.md	Marks eth_fillTransaction as implemented in the RPC support table.
.github/workflows/scripts/rpc_version.env	Changes the pinned rpc-tests version/branch used by CI workflows.

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[yperbasis]

Requesting changes — mostly mechanical, plus two items that need a decision. Implementation itself looks correct (builds clean, new tests pass, JSON shape matches Geth's types.Transaction output).

Blocking

• .github/workflows/scripts/rpc_version.env is pinned to a feature branch (lupin012/add_test_eth_fillTransaction) and adds a stray trailing newline. Branch pins make CI non-reproducible and break if the branch moves — please cut a tag in rpc-tests and pin to it before merge (as the PR description already plans).
• The branch currently conflicts with main (needs a rebase/merge).

Please address or reply

• gasPrice + accessList post-London: the shared ToTransaction returns an AccessListTx (type 1) where Geth forces LegacyTx (type 0). Sahil-4555's thread on this is still open — please make an explicit call and document the divergence. (Note Geth's path drops the access list, so blindly matching it isn't clearly better.)
• The nonce-filling block in eth_fill_transaction.go re-implements what GetTransactionCount already does for pending (rpc/jsonrpc/eth_accounts.go:99-111: txpool nonce+1 → state fallback). Suggest reusing it — simpler, and it propagates the pool error like Geth instead of silently falling back to the on-chain nonce.

Minor / non-blocking

• SignTransactionResult.MarshalJSON: the marshal → map → strip → re-marshal denylist will silently leak any future block-placement field added to RPCTransaction into the output. A dedicated typed output struct would be more robust.
• raw field: ethereum/execution-apis#803 drops it from FillTransactionResult. Keeping it to match current Geth is fine, but it's a known future breaking change for a new method — worth linking a tracking issue.

[lupin012]

@yperbasis
Blocking: rebase done, The rpc-tests version will be tagged and rpc_version.env updated to a stable tag once the PR is approved to avoid to block the main rpctests waiting approval of the PR
Please address or reply: done
Minor / non-blocking:
add signedTxJSON, open issue 21948

[yperbasis]

Thanks for this. A few correctness and test-quality issues to sort out before it can go in — details inline.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

[yperbasis]

A few changes before merge:

• signedTxJSON (rpc/ethapi/api.go) duplicates RPCTransaction and diverges from Geth's output shape. It's a hand-maintained parallel copy of the fields — if RPCTransaction ever gains a field, eth_fillTransaction silently drops it (no compile error, no test failure). It also drops omitempty from gasPrice/maxFeePerGas/maxPriorityFeePerGas, so a 1559 tx emits "gasPrice": null and a legacy tx emits "maxFeePerGas": null / "maxPriorityFeePerGas": null. Geth instead omits the inapplicable 1559 fields on a legacy tx and sets gasPrice to the fee cap on an unmined 1559 tx (here computeGasPrice returns nil because FillTransaction calls NewRPCTransaction with baseFee == nil). Please confirm the reference rpc-tests expect this exact shape, or marshal RPCTransaction and strip the unwanted keys so new fields flow through automatically.

• FillTransaction estimates gas against latest but takes the nonce from pending. EstimateGas(ctx, &args, nil, …) defaults to the latest block, while the nonce comes from GetTransactionCount(…, PendingBlockNumber). For a sender with in-flight pending txs the estimate can be wrong or fail even though the tx would succeed once those land — the two should use the same block.

• newGasOracle duplicates oracle construction already written verbatim three times in eth_system.go (GasPrice, MaxPriorityFeePerGas, FeeHistory). Route those call sites through the new helper so the wiring lives in one place and can't drift.

• Comment policy (.claude/rules/comments.md): the "Deliberate divergence from Geth …" comment on ToTransaction is PR-description narration and is repeated verbatim in the test — trim it to one sentence and drop the test copy.

• Nit: the new files carry // Copyright 2024 The Erigon Authors — should be 2026.

[yperbasis]

Approving — implementation is solid and well-tested.

One thing worth confirming before tagging the rpc-tests version: the blob fee default in eth_fill_transaction.go diverges from Geth in two ways. Erigon computes maxFeePerBlobGas as 2 × GetBlobGasPrice(CalcExcessBlobGas(next block)) — basing it on the next block's excess blob gas and doubling the result. Geth's setFeeDefaults uses eip4844.CalcBlobFee(config, head) on the head block with no doubling (it only doubles the regular maxFeePerGas). Since the new rpc-tests compare against Geth's response, a blob-fill case would return a larger value and mismatch. TestFillTransactionBlobFeeUsesNextBlockExcess only pins Erigon's own chosen value, so it won't catch this. If the divergence is intentional, a note in the README entry would help.

[lupin012]

@yperbasis: aligned blob fee default to Geth:

• use head ExcessBlobGas directly;
• keep 2× fee on maxFeePerBlobGas as Geth does