rpc, test: Fix error message in unloadwallet

The unloadwallet RPC previously failed with a low-level JSON parsing error
when called without any arguments (wallet_name).

Although this issue was first identified during review of the original unloadwallet
implementation in #13111, it was never addressed.

Raise RPC_INVALID_PARAMETER instead describing that either the RPC endpoint or wallet
name must be provided.

Adding a new functional test for this use case.

Refactor migratewallet to use the same logic as the wallet_name argument handling
is identical.

Co-authored-by:  maflcko <maflcko@users.noreply.github.com>

src/wallet/rpc/wallet.cpp

@@ -438,8 +438,8 @@ static RPCHelpMan createwallet()
 static RPCHelpMan unloadwallet()
 {
     return RPCHelpMan{"unloadwallet",
-                "Unloads the wallet referenced by the request endpoint, otherwise unloads the wallet specified in the argument.\n"
+                "Unloads the wallet referenced by the request endpoint or the wallet_name argument.\n"
-                "Specifying the wallet name on a wallet endpoint is invalid.",
+                "If both are specified, they must be identical.",
                 {
                     {"wallet_name", RPCArg::Type::STR, RPCArg::DefaultHint{"the wallet name from the RPC endpoint"}, "The name of the wallet to unload. If provided both here and in the RPC endpoint, the two must be identical."},
                     {"load_on_startup", RPCArg::Type::BOOL, RPCArg::Optional::OMITTED, "Save wallet name to persistent settings and load on startup. True to add wallet to startup list, false to remove, null to leave unchanged."},
@@ -456,14 +456,7 @@ static RPCHelpMan unloadwallet()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    std::string wallet_name;
+    const std::string wallet_name{EnsureUniqueWalletName(request, self.MaybeArg<std::string>("wallet_name"))};
-    if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
-        if (!(request.params[0].isNull() || request.params[0].get_str() == wallet_name)) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "RPC endpoint wallet and wallet_name parameter specify different wallets");
-        }
-    } else {
-        wallet_name = request.params[0].get_str();
-    }
 
     WalletContext& context = EnsureWalletContext(request.context);
     std::shared_ptr<CWallet> wallet = GetWallet(context, wallet_name);
@@ -685,17 +678,7 @@ static RPCHelpMan migratewallet()
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
-            std::string wallet_name;
+            const std::string wallet_name{EnsureUniqueWalletName(request, self.MaybeArg<std::string>("wallet_name"))};
-            if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
-                if (!(request.params[0].isNull() || request.params[0].get_str() == wallet_name)) {
-                    throw JSONRPCError(RPC_INVALID_PARAMETER, "RPC endpoint wallet and wallet_name parameter specify different wallets");
-                }
-            } else {
-                if (request.params[0].isNull()) {
-                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Either RPC endpoint wallet or wallet_name parameter must be provided");
-                }
-                wallet_name = request.params[0].get_str();
-            }
 
             SecureString wallet_pass;
             wallet_pass.reserve(100);

test/functional/wallet_migration.py

@@ -518,8 +518,8 @@ class WalletMigrationTest(BitcoinTestFramework):
     def test_nonexistent(self):
         self.log.info("Check migratewallet errors for nonexistent wallets")
         default = self.master_node.get_wallet_rpc(self.default_wallet_name)
-        assert_raises_rpc_error(-8, "RPC endpoint wallet and wallet_name parameter specify different wallets", default.migratewallet, "someotherwallet")
+        assert_raises_rpc_error(-8, "The RPC endpoint wallet and the wallet name parameter specify different wallets", default.migratewallet, "someotherwallet")
-        assert_raises_rpc_error(-8, "Either RPC endpoint wallet or wallet_name parameter must be provided", self.master_node.migratewallet)
+        assert_raises_rpc_error(-8, "Either the RPC endpoint wallet or the wallet name parameter must be provided", self.master_node.migratewallet)
         assert_raises_rpc_error(-4, "Error: Wallet does not exist", self.master_node.migratewallet, "notawallet")
 
     def test_unloaded_by_path(self):

test/functional/wallet_multiwallet.py

@@ -343,10 +343,10 @@ class MultiWalletTest(BitcoinTestFramework):
         self.log.info("Test dynamic wallet unloading")
 
         # Test `unloadwallet` errors
-        assert_raises_rpc_error(-3, "JSON value of type null is not of expected type string", self.nodes[0].unloadwallet)
+        assert_raises_rpc_error(-8, "Either the RPC endpoint wallet or the wallet name parameter must be provided", self.nodes[0].unloadwallet)
         assert_raises_rpc_error(-18, "Requested wallet does not exist or is not loaded", self.nodes[0].unloadwallet, "dummy")
         assert_raises_rpc_error(-18, "Requested wallet does not exist or is not loaded", node.get_wallet_rpc("dummy").unloadwallet)
-        assert_raises_rpc_error(-8, "RPC endpoint wallet and wallet_name parameter specify different wallets", w1.unloadwallet, "w2"),
+        assert_raises_rpc_error(-8, "The RPC endpoint wallet and the wallet name parameter specify different wallets", w1.unloadwallet, "w2"),
 
         # Successfully unload the specified wallet name
         self.nodes[0].unloadwallet("w1")