flash loan: Add a "swap without fees" option (#882)

mango_v4.json

@@ -10580,6 +10580,9 @@
           },
           {
             "name": "Swap"
+          },
+          {
+            "name": "SwapWithoutFee"
           }
         ]
       }

programs/mango-v4/src/accounts_ix/flash_loan.rs

@@ -92,6 +92,12 @@ pub struct FlashLoanEnd<'info> {
 #[derive(PartialEq, Copy, Clone, Debug, AnchorSerialize, AnchorDeserialize)]
 #[repr(u8)]
 pub enum FlashLoanType {
+    /// An arbitrary flash loan
     Unknown,
+    /// A flash loan used for a swap where one token is exchanged for another.
+    ///
+    /// Deposits in this type get charged the flash_loan_swap_fee_rate
     Swap,
+    /// Like Swap, but without the flash_loan_swap_fee_rate
+    SwapWithoutFee,
 }

programs/mango-v4/src/instructions/flash_loan.rs

@@ -378,10 +378,10 @@ pub fn flash_loan_end<'key, 'accounts, 'remaining, 'info>(
 
     match flash_loan_type {
         FlashLoanType::Unknown => {}
-        FlashLoanType::Swap => {
+        FlashLoanType::Swap | FlashLoanType::SwapWithoutFee => {
             require_msg!(
                 changes.len() == 2,
-                "when flash_loan_type is Swap there must be exactly 2 token vault changes"
+                "when flash_loan_type is Swap or SwapWithoutFee there must be exactly 2 token vault changes"
             )
         }
     }

ts/client/src/mango_v4.ts

@@ -10580,6 +10580,9 @@ export type MangoV4 = {
           },
           {
             "name": "Swap"
+          },
+          {
+            "name": "SwapWithoutFee"
           }
         ]
       }
@@ -24755,6 +24758,9 @@ export const IDL: MangoV4 = {
           },
           {
             "name": "Swap"
+          },
+          {
+            "name": "SwapWithoutFee"
           }
         ]
       }

ts/client/src/types.ts

@@ -9,11 +9,13 @@ export class FlashLoanWithdraw {
 
 export type FlashLoanType =
   | { unknown: Record<string, never> }
-  | { swap: Record<string, never> };
+  | { swap: Record<string, never> }
+  | { swapWithoutFee: Record<string, never> };
 // eslint-disable-next-line @typescript-eslint/no-namespace
 export namespace FlashLoanType {
   export const unknown = { unknown: {} };
   export const swap = { swap: {} };
+  export const swapWithoutFee = { swapWithoutFee: {} };
 }
 
 export class InterestRateParams {