Fix claimpegin and createrawpegin support for multiwallet.

src/wallet/rpcwallet.cpp

@@ -5554,6 +5554,12 @@ extern UniValue sendrawtransaction(const JSONRPCRequest& request);
 template<typename T_tx_ref, typename T_tx, typename T_merkle_block>
 static UniValue createrawpegin(const JSONRPCRequest& request, T_tx_ref& txBTCRef, T_tx& tx_aux, T_merkle_block& merkleBlock)
 {
+    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+    CWallet* const pwallet = wallet.get();
+
+    if (!EnsureWalletIsAvailable(pwallet, request.fHelp))
+        return NullUniValue;
+
     if (request.fHelp || request.params.size() < 2 || request.params.size() > 3)
         throw std::runtime_error(
             RPCHelpMan{"createrawpegin",
@@ -5577,9 +5583,6 @@ static UniValue createrawpegin(const JSONRPCRequest& request, T_tx_ref& txBTCRef
                 },
             }.ToString());
 
-    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
-    CWallet* const pwallet = wallet.get();
-
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
@@ -5695,6 +5698,11 @@ UniValue createrawpegin(const JSONRPCRequest& request)
 
 UniValue claimpegin(const JSONRPCRequest& request)
 {
+    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+    CWallet* const pwallet = wallet.get();
+
+    if (!EnsureWalletIsAvailable(pwallet, request.fHelp))
+        return NullUniValue;
 
     if (request.fHelp || request.params.size() < 2 || request.params.size() > 3)
         throw std::runtime_error(
@@ -5716,8 +5724,6 @@ UniValue claimpegin(const JSONRPCRequest& request)
                 },
             }.ToString());
 
-    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
-    CWallet* const pwallet = wallet.get();
     CTransactionRef tx_ref;
     CMutableTransaction mtx;
 
@@ -5728,20 +5734,30 @@ UniValue claimpegin(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_WALLET_ERROR, "Peg-ins cannot be completed during initial sync or reindexing.");
     }
 
+    // NOTE: Making an RPC from within another RPC is not generally a good idea. In particular, it
+    //   is necessary to copy the URI, which contains the wallet if one was given; otherwise
+    //   multi-wallet support will silently break. The resulting request object is still missing a
+    //   bunch of other fields, although they are usually not used by RPC handlers. This is a
+    //   brittle hack, and further examples of this pattern should not be introduced.
+
     // Get raw peg-in transaction
-    UniValue ret(createrawpegin(request));
+    JSONRPCRequest req;
+    req.URI = request.URI;
+    req.params = request.params;
+    UniValue ret(createrawpegin(req));  // See the note above, on why this is a bad idea.
 
     // Make sure it can be propagated and confirmed
     if (!ret["mature"].isNull() && ret["mature"].get_bool() == false) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Peg-in Bitcoin transaction needs more confirmations to be sent.");
     }
 
     // Sign it
-    JSONRPCRequest request2;
+    JSONRPCRequest req2;
+    req2.URI = request.URI;
     UniValue varr(UniValue::VARR);
     varr.push_back(ret["hex"]);
-    request2.params = varr;
-    UniValue result = signrawtransactionwithwallet(request2);
+    req2.params = varr;
+    UniValue result = signrawtransactionwithwallet(req2);  // See the note above, on why this is a bad idea.
 
     if (!DecodeHexTx(mtx, result["hex"].get_str(), false, true)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");

test/functional/feature_fedpeg.py

@@ -229,6 +229,14 @@ def run_test(self):
 
         raw = parent.gettransaction(txid1)["hex"]
 
+        # Create a wallet in order to test that multi-wallet support works correctly for claimpegin
+        #   (Regression test for https://github.com/ElementsProject/elements/issues/812 .)
+        sidechain.createwallet("throwaway")
+        # Set up our sidechain RPCs to use the first wallet (with empty name). We do this by
+        #   overriding the RPC object in a hacky way, to avoid breaking a different hack on TestNode
+        #   that enables generate() to work despite the deprecation of the generate RPC.
+        sidechain.rpc = sidechain.get_wallet_rpc("")
+
         print("Attempting peg-ins")
         # First attempt fails the consensus check but gives useful result
         try: