rpc: Add specific error code for "wallet already loaded"

src/rpc/protocol.h

@@ -79,6 +79,7 @@ enum RPCErrorCode
     RPC_WALLET_ALREADY_UNLOCKED     = -17, //!< Wallet is already unlocked
     RPC_WALLET_NOT_FOUND            = -18, //!< Invalid wallet specified
     RPC_WALLET_NOT_SPECIFIED        = -19, //!< No wallet specified (error when there are multiple wallets loaded)
+    RPC_WALLET_ALREADY_LOADED       = -35, //!< This same wallet is already loaded
 
     //! Backwards compatible aliases
     RPC_WALLET_INVALID_ACCOUNT_NAME = RPC_WALLET_INVALID_LABEL_NAME,

src/wallet/rpcwallet.cpp

@@ -2615,7 +2615,18 @@ static RPCHelpMan loadwallet()
     if (!wallet) {
         // Map bad format to not found, since bad format is returned when the
         // wallet directory exists, but doesn't contain a data file.
-        RPCErrorCode code = status == DatabaseStatus::FAILED_NOT_FOUND || status == DatabaseStatus::FAILED_BAD_FORMAT ? RPC_WALLET_NOT_FOUND : RPC_WALLET_ERROR;
+        RPCErrorCode code = RPC_WALLET_ERROR;
+        switch (status) {
+            case DatabaseStatus::FAILED_NOT_FOUND:
+            case DatabaseStatus::FAILED_BAD_FORMAT:
+                code = RPC_WALLET_NOT_FOUND;
+                break;
+            case DatabaseStatus::FAILED_ALREADY_LOADED:
+                code = RPC_WALLET_ALREADY_LOADED;
+                break;
+            default: // RPC_WALLET_ERROR is returned for all other cases.
+                break;
+        }
         throw JSONRPCError(code, error.original);
     }
 

test/functional/wallet_multiwallet.py

@@ -304,12 +304,12 @@ class MultiWalletTest(BitcoinTestFramework):
         if self.options.descriptors:
             assert_raises_rpc_error(-4, "Wallet file verification failed. SQLiteDatabase: Unable to obtain an exclusive lock on the database, is it being used by another bitcoind?", self.nodes[0].loadwallet, wallet_names[0])
         else:
-            assert_raises_rpc_error(-4, "Wallet file verification failed. Refusing to load database. Data file '{}' is already loaded.".format(path), self.nodes[0].loadwallet, wallet_names[0])
+            assert_raises_rpc_error(-35, "Wallet file verification failed. Refusing to load database. Data file '{}' is already loaded.".format(path), self.nodes[0].loadwallet, wallet_names[0])
 
             # This tests the default wallet that BDB makes, so SQLite wallet doesn't need to test this
             # Fail to load duplicate wallets by different ways (directory and filepath)
             path = os.path.join(self.options.tmpdir, "node0", "regtest", "wallets", "wallet.dat")
-            assert_raises_rpc_error(-4, "Wallet file verification failed. Refusing to load database. Data file '{}' is already loaded.".format(path), self.nodes[0].loadwallet, 'wallet.dat')
+            assert_raises_rpc_error(-35, "Wallet file verification failed. Refusing to load database. Data file '{}' is already loaded.".format(path), self.nodes[0].loadwallet, 'wallet.dat')
 
             # Only BDB doesn't open duplicate wallet files. SQLite does not have this limitation. While this may be desired in the future, it is not necessary
             # Fail to load if one wallet is a copy of another