Merge #20964: rpc: Add specific error code for "wallet already loaded"

a6739cc86827759c543bf81f5532ec46e40549c3 rpc: Add specific error code for "wallet already loaded" (Wladimir J. van der Laan)

Pull request description:

  Add a separate RPC error code for "wallet already loaded" to avoid having to match on message to detect this.
  Requested by shesek for rust-bitcoinrpc.

  If concept ACKed needs:
  - [ ]  Release note
  - [x]  A functional test (updated the existing test to make it pass, I think this is enough)

ACKs for top commit:
  jonasschnelli:
    Code Review ACK a6739cc86827759c543bf81f5532ec46e40549c3
  promag:
    Code review ACK a6739cc86827759c543bf81f5532ec46e40549c3.

Tree-SHA512: 9091872e6ea148aec733705d6af330f72a02f23b936b892ac28f9023da7430af6332418048adbee6014305b812316391812039e9180f7f3362d11f206c13b7d0

3 files changed, 15 insertions, 3 deletions

diff --git a/src/rpc/protocol.h b/src/rpc/protocol.h
index c8ceb2c186..fc00a1efad 100644
--- a/src/rpc/protocol.h
+++ b/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,
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index b865130642..ec51ba0453 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/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);
     }
 
diff --git a/test/functional/wallet_multiwallet.py b/test/functional/wallet_multiwallet.py
index bb89e76a9a..bf24b9c7b3 100755
--- a/test/functional/wallet_multiwallet.py
+++ b/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