feat: lending minimum loan #6155

j4m1ef0rd · 2025-10-04T02:56:08Z

Pull Request

Closes: PRO-2545

Checklist

Please conduct a thorough self-review before opening the PR.

I am confident that the code works.
I have written sufficient tests.

Summary

To prevent spam, we have added 3 new minimums in the config:

minimum_loan_amount_usd: Minimum equivalent amount of principal that a loan must be left with after expanding or repaying (unless fully repaying).
minimum_update_loan_amount_usd: Minimum equivalent amount of principal that can be used to expand or repay an existing loan (unless fully repaying).
minimum_update_collateral_amount_usd: Minimum equivalent amount of collateral that can be added or removed from a loan account (unless fully removing).

Added tests to cover all new code. Added to the config RPC. Added to the update config extrinsic.

coderabbitai · 2025-10-04T02:56:59Z

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codecov · 2025-10-04T03:12:07Z

Codecov Report

❌ Patch coverage is 93.91026% with 19 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
state-chain/pallets/cf-lending-pools/src/lib.rs	56%	8 Missing ⚠️
...in/pallets/cf-lending-pools/src/general_lending.rs	84%	0 Missing and 7 partials ⚠️
state-chain/runtime/src/lib.rs	0%	0 Missing and 3 partials ⚠️
...pools/src/general_lending/general_lending_tests.rs	99%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

msgmaxim · 2025-10-09T00:06:16Z

state-chain/pallets/cf-lending-pools/src/general_lending/general_lending_tests.rs


-use crate::LENDING_DEFAULT_CONFIG as CONFIG;
+/// Default config with minimum loan/update amounts set to zero
+fn config() -> LendingConfiguration {


Why does this have to be a function? You could still keep it as CONFIG constant iniialising it to

LendingConfiguration { // Set the loan minimums to zero by default for tests minimum_loan_amount_usd: 0, minimum_update_loan_amount_usd: 0, ..LENDING_DEFAULT_CONFIG }

Then most of the rest of the test code wouldn't need to change.

I did try this already, it has an error:
destructor of general_lending::LendingConfiguration cannot be evaluated at compile-time.
Seems like it should be possible but i'm not sure how to so it.

msgmaxim · 2025-10-09T00:10:34Z

state-chain/pallets/cf-lending-pools/src/general_lending/general_lending_tests.rs

+fn test_loan_minimum_is_enforced() {
+	const MIN_LOAN_AMOUNT_USD: AssetAmount = 1_000;
+	const MIN_LOAN_AMOUNT_ASSET: AssetAmount = MIN_LOAN_AMOUNT_USD / SWAP_RATE;
+	const COLLATERAL_ASSET: Asset = Asset::Eth;


I would just use the global COLLATERAL_ASSET (which also happens to be Asset::Eth). Otherwise re-defining it makes it look like the asset is important.

msgmaxim · 2025-10-09T00:22:26Z

state-chain/pallets/cf-lending-pools/src/general_lending.rs


 				T::Balance::credit_account(borrower_id, loan_asset, excess_amount);
+			} else {
+				let config = LendingConfig::<T>::get();


Should probably read config once at the top.

msgmaxim · 2025-10-09T00:23:10Z

state-chain/pallets/cf-lending-pools/src/general_lending.rs

 	pub fee_swap_max_oracle_slippage: BasisPoints,
 	/// If set for a pool/asset, this configuration will be used instead of the default
 	pub pool_config_overrides: BTreeMap<Asset, LendingPoolConfiguration>,
+	/// Minimum amount of principle that a loan must have at all times.


Suggested change

/// Minimum amount of principle that a loan must have at all times.

/// Minimum amount of principal that a loan must have at all times.

msgmaxim · 2025-10-09T00:38:07Z

You will need to update RpcLendingConfig too so the new fields are correctly exposed via RPC (and update the snapshots) @j4m1ef0rd

msgmaxim · 2025-10-13T00:58:16Z

state-chain/pallets/cf-lending-pools/src/general_lending/general_lending_tests.rs


-		const ORIGINATION_FEE: AssetAmount =
-			portion_of_amount(DEFAULT_ORIGINATION_FEE, PRINCIPAL) * SWAP_RATE;
+		let origination_fee = CONFIG.origination_fee(LOAN_ASSET) * PRINCIPAL * SWAP_RATE;


What was the reason for this change?

left over from when config was not const. I will revert it.

msgmaxim · 2025-10-13T01:00:09Z

state-chain/pallets/cf-lending-pools/src/general_lending.rs

+	let mut total_collateral_usd = 0;
+	for (asset, amount) in assets_amounts {
+		total_collateral_usd =
+			total_collateral_usd.saturating_add(usd_value_of::<T>(*asset, *amount)?);


You can use saturating_accrue

msgmaxim · 2025-10-13T01:05:03Z

state-chain/pallets/cf-lending-pools/src/general_lending.rs

+			if repayment_amount < loan.owed_principal {
+				ensure!(
+					repayment_amount >=
+						amount_from_usd_value::<T>(


IMO using usd_value_of here and below would be more natural (e.g. it is slightly more efficient as it doesn't need to invert the price).

msgmaxim · 2025-10-13T01:10:40Z

state-chain/runtime/src/runtime_apis.rs

 	/// All fee swaps from lending will be executed with this oracle slippage limit
 	pub fee_swap_max_oracle_slippage: BasisPoints,
+	/// Minimum equivalent amount of principal that a loan must have at all times.
+	pub minimum_loan_amount_usd: AssetAmount,


I think we want all amounts to be in U256 (so they are encoded as hex). See how it is done for liquidation_swap_chunk_size_usd.

msgmaxim · 2025-10-16T03:36:42Z

state-chain/pallets/cf-lending-pools/src/general_lending.rs


 		loan.owed_principal.saturating_accrue(extra_principal);

+		ensure!(


Maybe this should be done in new_loan rather than expand_loan? I know this covers an additional edge case where we have a small loan to begin with, but not sure if we should be preventing the user from addint to a small loan if we already have it (it is not making anything worse). Then putting it in new_loan would look more natural.

msgmaxim · 2025-10-16T03:41:41Z

state-chain/pallets/cf-lending-pools/src/general_lending.rs

 				Error::<T>::LiquidationInProgress
 			);

+			let total_collateral_usd = total_usd_value_of::<T>(&collateral)?;


Would it be better to simply check collateral == loan_account.collateral instead of calculating total usd value of loan_account.collateral? I know it won't make a big difference performance wise, but from readability standopint I think it would be an improvement.

but for which collateral asset do we check? it could be any of them, and checking each to see if its below the loans corresponding collateral asset would change the behaviour.

So the current/desired behaviour is to ensure that the value of the collateral removed is at least minimum_update_collateral_amount_usd, but we make an exception for the case where the user wants to remove all collateral, right? What I'm suggesting is that we can check if the exception rule applies by comparing the map of assets provided to loan_account.collateral instead of computing their values. You still need to compute the value of added collateral in the non-exceptional case of course.

However, this does make be think that we might want to interpret empty collateral as "withdraw everything" (it might be tricky to provide the exact amount considering that we charge interest).

msgmaxim · 2025-10-16T03:46:08Z

state-chain/pallets/cf-lending-pools/src/lib.rs

 	#[pallet::storage]
-	pub type LendingConfig<T: Config> =
-		StorageValue<_, LendingConfiguration, ValueQuery, LendingConfigDefault>;
+	pub type LendingConfig<T: Config> = StorageValue<_, LendingConfiguration, ValueQuery>;


We discussed this before I believe. Do we need this change? I think I'd rather provide LendingConfigDefault here explicitly rather than implementing Default which seems like it is not needed anywhere else.

j4m1ef0rd requested a review from msgmaxim October 4, 2025 02:56

j4m1ef0rd self-assigned this Oct 4, 2025

j4m1ef0rd requested a review from dandanlen as a code owner October 4, 2025 02:56

j4m1ef0rd added the State Chain label Oct 4, 2025

j4m1ef0rd changed the title ~~Feat lending minimum loan~~ feat: lending minimum loan Oct 4, 2025

j4m1ef0rd marked this pull request as draft October 6, 2025 01:57

msgmaxim force-pushed the feat/core-lending branch from fc5c46e to a8cd6be Compare October 6, 2025 06:49

j4m1ef0rd force-pushed the feat/lending-minimum-loan branch 2 times, most recently from 1daee51 to ab3dd07 Compare October 8, 2025 03:50

j4m1ef0rd marked this pull request as ready for review October 8, 2025 03:50

j4m1ef0rd force-pushed the feat/lending-minimum-loan branch from ab3dd07 to c0bfb53 Compare October 8, 2025 05:20

msgmaxim reviewed Oct 9, 2025

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j4m1ef0rd requested review from a team and nmammeri as code owners October 9, 2025 04:22

j4m1ef0rd force-pushed the feat/lending-minimum-loan branch from 86f8adb to 0469763 Compare October 9, 2025 05:35

msgmaxim reviewed Oct 13, 2025

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j4m1ef0rd force-pushed the feat/lending-minimum-loan branch from 9ea4a43 to e4dda45 Compare October 13, 2025 02:41

msgmaxim force-pushed the feat/core-lending branch from b99f2df to 403b6c2 Compare October 13, 2025 04:13

j4m1ef0rd force-pushed the feat/lending-minimum-loan branch 2 times, most recently from f3aa026 to f97ebaa Compare October 13, 2025 04:33

Base automatically changed from feat/core-lending to main October 15, 2025 10:10

j4m1ef0rd requested a review from albert-llimos as a code owner October 15, 2025 10:10

j4m1ef0rd added 5 commits October 16, 2025 13:01

feat: loan minimums for spam prevention

1d9d935

refactor: add to rpc lending config and address PR comments

061b5fd

chore: revert to const config for tests.

3bcc014

feat: added minimum for updating collateral

2af558e

refactor: address PR comments

599839a

j4m1ef0rd force-pushed the feat/lending-minimum-loan branch from f97ebaa to 599839a Compare October 16, 2025 02:01

msgmaxim reviewed Oct 16, 2025

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msgmaxim approved these changes Oct 16, 2025

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msgmaxim reviewed Oct 16, 2025

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	/// Minimum amount of principle that a loan must have at all times.
	/// Minimum amount of principal that a loan must have at all times.


		loan.owed_principal.saturating_accrue(extra_principal);

		ensure!(

feat: lending minimum loan #6155

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