fix: name the missing CounterpartySignature when a LoanSet is submitted without it

[kuan121]

High Level Overview of Change

submit and submitAndWait now throw a clear ValidationError when a LoanSet is submitted without the counterparty's signature, instead of passing on rippled's unrelated temBAD_SIGNER message.

Jira: DGE-8439

Context of Change

A LoanSet is signed twice: first by the Account, then by the counterparty through signLoanSetByCounterparty. A developer who forgets the second step and submits gets:

Transaction failed, temBAD_SIGNER: Malformed: No signer may duplicate account or other signers.

rippled returns temBAD_SIGNER from LoanSet::preflight when CounterpartySignature is missing outside a Batch (LoanSet.cpp:94-97), and the generic text for that code points at duplicate signers that don't exist. Three teams at the Lending Protocol hackathon lost time to this.

submitRequest, which both submit and submitAndWait call, now throws before sending:

LoanSet requires the counterparty's signature (CounterpartySignature). Use signLoanSetByCounterparty before submitting.

The condition mirrors rippled's: a top-level LoanSet with no CounterpartySignature and without tfInnerBatchTxn. Inner transactions of a Batch are not checked, since rippled lets an inner LoanSet omit the field. validate() and Wallet.sign() are unchanged: the Account signs before the counterparty does, so a LoanSet without CounterpartySignature is valid until it is submitted.

Type of Change

• Bug fix (non-breaking change which fixes an issue)

One behaviour change: for this input, submit used to resolve with engine_result: temBAD_SIGNER, and it now rejects without sending anything. rippled rejects such a LoanSet in every case, so no working code path changes. ValidationError extends XrplError, so submitAndWait callers catching XrplError still catch it.

The existing multi-signing step in lendingProtocol.test.ts that asserted temBAD_SIGNER for an unsigned-by-counterparty LoanSet now asserts the new error.

Did you update HISTORY.md?

• Yes

Test Plan

Unit tests in test/client/submit.test.ts:

• A LoanSet signed only by the Account throws the new error, whether submitted as a blob or signed during submit with a wallet.
• A LoanSet signed by the counterparty is submitted.
• A Batch whose inner LoanSet has no CounterpartySignature is submitted.

Integration: the updated step in test/integration/transactions/lendingProtocol.test.ts.

The unit test fails on main and passes with the fix. I ran it locally against rippleci/xrpld:develop --standalone (xrpld 3.4.0-rc1), together with the lending, submit, submitAndWait and Batch integration suites. The xrpl unit suite (134 suites, 1346 tests) and lint also pass.

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📥 Commits

Reviewing files that changed from the base of the PR and between cfd0fb4 and 80af91b.

📒 Files selected for processing (4)

• packages/xrpl/HISTORY.md
• packages/xrpl/src/sugar/submit.ts
• packages/xrpl/test/client/submit.test.ts
• packages/xrpl/test/integration/transactions/lendingProtocol.test.ts

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Walkthrough

Submission validation now raises ValidationError when a LoanSet lacks CounterpartySignature. The check excludes inner Batch transactions. Tests cover unsigned and counterparty-signed submissions, including the Batch exception.

Changes

LoanSet Signature Validation

Layer / File(s)	Summary
Add the LoanSet signature check packages/xrpl/src/sugar/submit.ts	submitRequest checks for a missing CounterpartySignature and raises ValidationError. The helper excludes inner Batch transactions and decodes string transaction inputs.
Verify submission outcomes packages/xrpl/test/client/submit.test.ts, packages/xrpl/test/integration/transactions/lendingProtocol.test.ts, packages/xrpl/HISTORY.md	Client tests cover rejection without the counterparty signature, acceptance with the signature, and the inner Batch exception. The integration test now expects ValidationError instead of temBAD_SIGNER. The changelog records the behavior.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~12 minutes

Change: Bug fix

Suggested reviewers: mvadari

Merge Risk: ⚪ Minimal · up to 80af9

The LoanSet submission change is mergeable after normal checks; no unresolved issue is established.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: naming the missing CounterpartySignature for submitted LoanSet transactions.
Description check	✅ Passed	The description includes the required overview, context, change type, HISTORY.md status, and test plan. It explains the behavior change, affected APIs, Batch exception, and test coverage.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 3 files. (1 skipped: 1 …
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[xrplf-ai-reviewer]

The change adds a client-side pre-check in submitRequest that throws a clear ValidationError when a top-level LoanSet lacks CounterpartySignature and isn't an inner Batch transaction (checked via tfInnerBatchTxn), replacing the opaque temBAD_SIGNER rippled error. The logic correctly mirrors rippled's LoanSet::preflight condition, and the top-level TransactionType check naturally excludes Batch submissions from the new check (since the submitted blob's type is Batch, not LoanSet), consistent with the stated intent that inner LoanSets aren't checked. HISTORY.md is updated, and unit/integration tests cover the unsigned, counterparty-signed, and Batch-inner-LoanSet cases. I did not find correctness, security, or consistency issues in the added code worth flagging.