Merge bitcoin/bitcoin#26192: rpc: Improve error when wallet is already loaded

0460928 rpc: Improve error when wallet is already loaded (Aurèle Oulès)

Pull request description:

  Currently, trying to load a descriptor (sqlite) wallet that is already loaded throws the following error:
  > error code: -4
  > error message:
  > Wallet file verification failed. SQLiteDatabase: Unable to obtain an exclusive lock on the database, is it being used by another instance of Bitcoin Core?

  I don't think it is very clear what it means for a user.

  While a legacy wallet would throw:
  > error code: -35
  > error message:
  > Wallet file verification failed. Refusing to load database. Data file '/home/user/.bitcoin/signet/wallets/test_wallet/wallet.dat' is already loaded.

  This PR changes the error message for both types of wallet to:
  > error code: -35
  > error message:
  > Wallet file verification failed. Wallet "test_wallet" is already loaded.

ACKs for top commit:
  achow101:
    ACK 0460928
  hernanmarino:
    ACK  0460928
  theStack:
    Tested ACK 0460928

Tree-SHA512: a8f3d5133bfaef7417a6c05d160910ea08f32ac62bfdf7f5ec305ff5b62e9113b55f385abab4d5a4ad711aabcb1eb7ef746eb41f841b196e8fb5393ab3ccc01e

Author: achow101

src/wallet/rpc/wallet.cpp

@@ -226,6 +226,14 @@ static RPCHelpMan loadwallet()
     bilingual_str error;
     std::vector<bilingual_str> warnings;
     std::optional<bool> load_on_start = request.params[1].isNull() ? std::nullopt : std::optional<bool>(request.params[1].get_bool());
+
+    {
+        LOCK(context.wallets_mutex);
+        if (std::any_of(context.wallets.begin(), context.wallets.end(), [&name](const auto& wallet) { return wallet->GetName() == name; })) {
+            throw JSONRPCError(RPC_WALLET_ALREADY_LOADED, "Wallet \"" + name + "\" is already loaded.");
+        }
+    }
+
     std::shared_ptr<CWallet> const wallet = LoadWallet(context, name, load_on_start, options, status, error, warnings);
 
     HandleWalletError(wallet, status, error);

test/functional/wallet_multiwallet.py

@@ -303,12 +303,8 @@ def wallet_file(name):
         assert_raises_rpc_error(-18, "Wallet file verification failed. Failed to load database path '{}'. Path does not exist.".format(path), self.nodes[0].loadwallet, 'wallets')
 
         # Fail to load duplicate wallets
-        path = os.path.join(self.options.tmpdir, "node0", "regtest", "wallets", "w1", "wallet.dat")
-        if self.options.descriptors:
-            assert_raises_rpc_error(-4, f"Wallet file verification failed. SQLiteDatabase: Unable to obtain an exclusive lock on the database, is it being used by another instance of {self.config['environment']['PACKAGE_NAME']}?", self.nodes[0].loadwallet, wallet_names[0])
-        else:
-            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])
-
+        assert_raises_rpc_error(-35, "Wallet \"w1\" is already loaded.", self.nodes[0].loadwallet, wallet_names[0])
+        if not self.options.descriptors:
             # 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")