prevent users from withdrawing from empty reward accounts.

lib/core/src/Cardano/Wallet.hs

@@ -114,6 +114,7 @@ module Cardano.Wallet
     , ErrValidateSelection
     , ErrNotASequentialWallet (..)
     , ErrUTxOTooSmall (..)
+    , ErrWithdrawalNotWorth (..)
 
     -- ** Migration
     , selectCoinsForMigration
@@ -2287,6 +2288,10 @@ data ErrReadChimericAccount
     | ErrReadChimericAccountNoSuchWallet ErrNoSuchWallet
     deriving (Generic, Eq, Show)
 
+data ErrWithdrawalNotWorth
+    = ErrWithdrawalNotWorth
+    deriving (Generic, Eq, Show)
+
 {-------------------------------------------------------------------------------
                                    Utils
 -------------------------------------------------------------------------------}

lib/core/src/Cardano/Wallet/Api/Server.hs

@@ -133,6 +133,7 @@ import Cardano.Wallet
     , ErrWalletAlreadyExists (..)
     , ErrWalletNotResponding (..)
     , ErrWithRootKey (..)
+    , ErrWithdrawalNotWorth (..)
     , ErrWrongPassphrase (..)
     , FeeEstimation (..)
     , HasLogger
@@ -313,7 +314,7 @@ import Control.Concurrent.Async
 import Control.Exception
     ( IOException, bracket, throwIO, tryJust )
 import Control.Monad
-    ( forM, forever, void, (>=>) )
+    ( forM, forever, void, when, (>=>) )
 import Control.Monad.Catch
     ( handle )
 import Control.Monad.IO.Class
@@ -1241,6 +1242,9 @@ postTransaction ctx genChange (ApiT wid) body = do
                 (, const (xprv, mempty))
                     <$> liftIO (W.readNextWithdrawal @_ @s @t @k wrk wid wdrl)
 
+        when (isJust (body ^. #withdrawal) && wdrl == Quantity 0) $ do
+            liftHandler $ throwE ErrWithdrawalNotWorth
+
         selection <- liftHandler $ W.selectCoinsForPayment @_ @s @t wrk wid outs wdrl
         pure (selection, credentials)
 
@@ -2449,6 +2453,16 @@ instance LiftHandler ErrNotASequentialWallet where
                 , "Make sure to use a sequential wallet style, like Icarus."
                 ]
 
+instance LiftHandler ErrWithdrawalNotWorth where
+    handler = \case
+        ErrWithdrawalNotWorth ->
+            apiError err403 WithdrawalNotWorth $ mconcat
+                [ "I've noticed that you're requesting a withdrawal from an "
+                , "account that is either empty or doesn't have a balance big "
+                , "enough to deserve being withdrawn. I won't proceed with that "
+                , "request."
+                ]
+
 instance LiftHandler (Request, ServerError) where
     handler (req, err@(ServerError code _ body headers))
       | not (isJSON body) = case code of

lib/core/src/Cardano/Wallet/Api/Types.hs

@@ -681,6 +681,7 @@ data ApiErrorCode
     | UtxoTooSmall
     | MinWithdrawalWrong
     | AlreadyWithdrawing
+    | WithdrawalNotWorth
     deriving (Eq, Generic, Show)
 
 -- | Defines a point in time that can be formatted as and parsed from an