fix: check liquidity and allow 0 fee

Author: obycode

contracts/reservoir.clar

@@ -23,8 +23,7 @@
 ;; SOFTWARE.
 
 (use-trait sip-010 'SP3FBR2AGK5H9QBDH3EEN6DF8EK8JY7RX8QJ5SVTE.sip-010-trait-ft-standard.sip-010-trait)
-(use-trait stackflow-token .stackflow-token.stackflow-token)
-;; (use-trait stackflow-token 'SP126XFZQ3ZHYM6Q6KAQZMMJSDY91A8BTT6AD08RV.stackflow-token-0-6-0.stackflow-token)
+(use-trait stackflow-token 'SP126XFZQ3ZHYM6Q6KAQZMMJSDY91A8BTT6AD08RV.stackflow-token-0-6-0.stackflow-token)
 
 (define-constant OPERATOR tx-sender)
 (define-constant RESERVOIR current-contract)
@@ -395,6 +394,7 @@
 ;;; tap.
 ;;; Returns:
 ;;; -`(ok expire-block)` on success
+;;; - `ERR_AMOUNT_NOT_AVAILABLE` if reservoir liquidity is below `amount`
 ;;; - `ERR_BORROW_FEE_PAYMENT_FAILED` if the fee payment failed
 ;;; - Errors passed through from the StackFlow `deposit` function
 (define-public (borrow-liquidity
@@ -411,11 +411,16 @@
   (let (
       (borrower tx-sender)
       (expected-fee (get-borrow-fee amount))
+      (available-liquidity (unwrap-panic (get-available-liquidity token)))
       (until (+ burn-block-height BORROW_TERM_BLOCKS))
     )
     (try! (check-valid stackflow token))
+    (asserts! (<= amount available-liquidity) ERR_AMOUNT_NOT_AVAILABLE)
     (asserts! (>= fee expected-fee) ERR_INVALID_FEE)
-    (unwrap! (transfer-to-contract token fee) ERR_BORROW_FEE_PAYMENT_FAILED)
+    (if (is-eq fee u0)
+      true
+      (unwrap! (transfer-to-contract token fee) ERR_BORROW_FEE_PAYMENT_FAILED)
+    )
     (try! (match token
       t (as-contract? ((with-ft (contract-of t) "*" amount))
         (try! (contract-call? stackflow deposit amount token borrower reservoir-balance

deployments/default.simnet-plan.yaml

@@ -93,11 +93,6 @@ plan:
       emulated-sender: SP126XFZQ3ZHYM6Q6KAQZMMJSDY91A8BTT6AD08RV
       path: ./.cache/requirements/SP126XFZQ3ZHYM6Q6KAQZMMJSDY91A8BTT6AD08RV.stackflow-token-0-6-0.clar
       clarity-version: 4
-    - transaction-type: emulated-contract-publish
-      contract-name: stackflow-token
-      emulated-sender: ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM
-      path: contracts/stackflow-token.clar
-      clarity-version: 4
     - transaction-type: emulated-contract-publish
       contract-name: reservoir
       emulated-sender: ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM
@@ -113,6 +108,11 @@ plan:
       emulated-sender: ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM
       path: contracts/stackflow.clar
       clarity-version: 4
+    - transaction-type: emulated-contract-publish
+      contract-name: stackflow-token
+      emulated-sender: ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM
+      path: contracts/stackflow-token.clar
+      clarity-version: 4
     - transaction-type: emulated-contract-publish
       contract-name: test-token
       emulated-sender: ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM

tests/reservoir.test.ts

@@ -159,6 +159,14 @@ describe("reservoir", () => {
         address1
       );
 
+      // Add liquidity so amount check passes and we reach fee validation
+      simnet.callPublicFn(
+        "reservoir",
+        "add-liquidity",
+        [Cl.none(), Cl.uint(1000000)],
+        deployer
+      );
+
       const mySignature = generateDepositSignature(
         address1PK,
         null,
@@ -554,6 +562,89 @@ describe("reservoir", () => {
       );
     });
 
+    it("can borrow liquidity with zero fee when borrow rate is zero", () => {
+      // borrow-rate is u0 from init
+      const { result: feeResult } = simnet.callReadOnlyFn(
+        "reservoir",
+        "get-borrow-fee",
+        [Cl.uint(50000)],
+        deployer
+      );
+      expect(feeResult).toBeUint(0);
+
+      // Add liquidity to reservoir
+      simnet.callPublicFn(
+        "reservoir",
+        "add-liquidity",
+        [Cl.none(), Cl.uint(5000000000)],
+        deployer
+      );
+
+      // Fund initial tap
+      const { result } = simnet.callPublicFn(
+        "reservoir",
+        "create-tap",
+        [
+          Cl.principal(stackflowContract),
+          Cl.none(),
+          Cl.uint(1000000),
+          Cl.uint(0),
+        ],
+        address1
+      );
+      expect(result.type).toBe(ClarityType.ResponseOk);
+
+      const amount = 50000;
+      const fee = 0;
+
+      const mySignature = generateDepositSignature(
+        address1PK,
+        null,
+        address1,
+        reservoirContract,
+        1000000,
+        50000,
+        1,
+        reservoirContract
+      );
+
+      const reservoirSignature = generateDepositSignature(
+        deployerPK,
+        null,
+        reservoirContract,
+        address1,
+        50000,
+        1000000,
+        1,
+        reservoirContract
+      );
+
+      const borrow = simnet.callPublicFn(
+        "reservoir",
+        "borrow-liquidity",
+        [
+          Cl.principal(stackflowContract),
+          Cl.uint(amount),
+          Cl.uint(fee),
+          Cl.none(),
+          Cl.uint(1000000),
+          Cl.uint(50000),
+          Cl.buffer(mySignature),
+          Cl.buffer(reservoirSignature),
+          Cl.uint(1),
+        ],
+        address1
+      );
+      expect(borrow.result).toBeOk(
+        Cl.uint(simnet.burnBlockHeight + BORROW_TERM_BLOCKS)
+      );
+
+      // 5000000000 - 50000 (borrowed), with no fee transfer
+      const stxBalances = simnet.getAssetsMap().get("STX")!;
+      const reservoirBalance = stxBalances.get(reservoirContract);
+      expect(reservoirBalance).toBe(4999950000n);
+    });
+
     it("can borrow additional liquidity before previous term ends", () => {
       // Set rate to 10% and fund the reservoir
       simnet.callPublicFn(
@@ -764,7 +855,7 @@ describe("reservoir", () => {
         ],
         address1
       );
-      expect(result).toBeErr(Cl.uint(StackflowError.DepositFailed));
+      expect(result).toBeErr(Cl.uint(ReservoirError.AmountNotAvailable));
     });
   });