Merge #11050: Avoid treating null RPC arguments different from missing arguments

745d2e3 Clean up getbalance RPC parameter handling (Russell Yanofsky)
fd5d71e Update developer notes after params.size() cleanup (Russell Yanofsky)
e067673 Avoid treating null RPC arguments different from missing arguments (Russell Yanofsky)
e666efc Get rid of redundant RPC params.size() checks (Russell Yanofsky)

Pull request description:

  This is a followup to #10783.

  - The first commit doesn't change behavior at all, just simplifies code.
  - The second commit just changes RPC methods to treat null arguments the same as missing arguments instead of throwing type errors.
  - The third commit updates developer notes after the cleanup.
  - The forth commit does some additional code cleanup in `getbalance`.

  Followup changes that should happen in future PRs:

  - [ ] Replace uses of `.isTrue()` with calls to `.get_bool()` so numbers, objects, and strings cause type errors instead of being interpreted as false. https://github.com/bitcoin/bitcoin/pull/11050#discussion_r133850525
  - [ ] Add braces around if statements. https://github.com/bitcoin/bitcoin/pull/11050#discussion_r133851133
  - [ ] Maybe improve UniValue type error exceptions and eliminate RPCTypeCheck and RPCTypeCheckArgument functions. https://github.com/bitcoin/bitcoin/pull/11050#discussion_r133829303

Tree-SHA512: e72f696011d20acc0778e996659e41f9426bffce387b29ff63bf59ad1163d5146761e4445b2b9b9e069a80596a57c7f4402b75a15d5d20f69f775ae558cf67e9

7 files changed, 71 insertions, 61 deletions

diff --git a/doc/developer-notes.md b/doc/developer-notes.md
index 9b85600ccc..ad15aa662e 100644
--- a/doc/developer-notes.md
+++ b/doc/developer-notes.md
@@ -572,16 +572,14 @@ A few guidelines for introducing and reviewing new RPC interfaces:
     is specified as-is in BIP22.
 
 - Missing arguments and 'null' should be treated the same: as default values. If there is no
-  default value, both cases should fail in the same way.
+  default value, both cases should fail in the same way. The easiest way to follow this
+  guideline is detect unspecified arguments with `params[x].isNull()` instead of
+  `params.size() <= x`. The former returns true if the argument is either null or missing,
+  while the latter returns true if is missing, and false if it is null.
 
   - *Rationale*: Avoids surprises when switching to name-based arguments. Missing name-based arguments
   are passed as 'null'.
 
-  - *Exception*: Many legacy exceptions to this exist, one of the worst ones is
-    `getbalance` which follows a completely different code path based on the
-    number of arguments. We are still in the process of cleaning these up. Do not introduce
-    new ones.
-
 - Try not to overload methods on argument type. E.g. don't make `getblock(true)` and `getblock("hash")`
   do different things.
 
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 34bcdf9ccc..34f553f3b0 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1489,11 +1489,11 @@ UniValue getchaintxstats(const JSONRPCRequest& request)
     const CBlockIndex* pindex;
     int blockcount = 30 * 24 * 60 * 60 / Params().GetConsensus().nPowTargetSpacing; // By default: 1 month
 
-    if (request.params.size() > 0 && !request.params[0].isNull()) {
+    if (!request.params[0].isNull()) {
         blockcount = request.params[0].get_int();
     }
 
-    bool havehash = request.params.size() > 1 && !request.params[1].isNull();
+    bool havehash = !request.params[1].isNull();
     uint256 hash;
     if (havehash) {
         hash = uint256S(request.params[1].get_str());
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 652d886c7e..2692e59155 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -842,7 +842,7 @@ UniValue estimatesmartfee(const JSONRPCRequest& request)
     RPCTypeCheckArgument(request.params[0], UniValue::VNUM);
     unsigned int conf_target = ParseConfirmTarget(request.params[0]);
     bool conservative = true;
-    if (request.params.size() > 1 && !request.params[1].isNull()) {
+    if (!request.params[1].isNull()) {
         FeeEstimateMode fee_mode;
         if (!FeeModeFromString(request.params[1].get_str(), fee_mode)) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid estimate_mode parameter");
diff --git a/src/rpc/misc.cpp b/src/rpc/misc.cpp
index 1dd660eb8f..a6af24f7e1 100644
--- a/src/rpc/misc.cpp
+++ b/src/rpc/misc.cpp
@@ -552,7 +552,7 @@ UniValue getmemoryinfo(const JSONRPCRequest& request)
             + HelpExampleRpc("getmemoryinfo", "")
         );
 
-    std::string mode = (request.params.size() < 1 || request.params[0].isNull()) ? "stats" : request.params[0].get_str();
+    std::string mode = request.params[0].isNull() ? "stats" : request.params[0].get_str();
     if (mode == "stats") {
         UniValue obj(UniValue::VOBJ);
         obj.push_back(Pair("locked", RPCLockedMemoryInfo()));
@@ -603,11 +603,11 @@ UniValue logging(const JSONRPCRequest& request)
     }
 
     uint32_t originalLogCategories = logCategories;
-    if (request.params.size() > 0 && request.params[0].isArray()) {
+    if (request.params[0].isArray()) {
         logCategories |= getCategoryMask(request.params[0]);
     }
 
-    if (request.params.size() > 1 && request.params[1].isArray()) {
+    if (request.params[1].isArray()) {
         logCategories &= ~getCategoryMask(request.params[1]);
     }
 
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index e463a4eda4..f19b968244 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -193,7 +193,7 @@ UniValue getpeerinfo(const JSONRPCRequest& request)
 UniValue addnode(const JSONRPCRequest& request)
 {
     std::string strCommand;
-    if (request.params.size() == 2)
+    if (!request.params[1].isNull())
         strCommand = request.params[1].get_str();
     if (request.fHelp || request.params.size() != 2 ||
         (strCommand != "onetry" && strCommand != "add" && strCommand != "remove"))
@@ -258,7 +258,7 @@ UniValue disconnectnode(const JSONRPCRequest& request)
 
     bool success;
     const UniValue &address_arg = request.params[0];
-    const UniValue &id_arg = request.params.size() < 2 ? NullUniValue : request.params[1];
+    const UniValue &id_arg = request.params[1];
 
     if (!address_arg.isNull() && id_arg.isNull()) {
         /* handle disconnect-by-address */
@@ -311,7 +311,7 @@ UniValue getaddednodeinfo(const JSONRPCRequest& request)
 
     std::vector<AddedNodeInfo> vInfo = g_connman->GetAddedNodeInfo();
 
-    if (request.params.size() == 1 && !request.params[0].isNull()) {
+    if (!request.params[0].isNull()) {
         bool found = false;
         for (const AddedNodeInfo& info : vInfo) {
             if (info.strAddedNode == request.params[0].get_str()) {
@@ -490,7 +490,7 @@ UniValue getnetworkinfo(const JSONRPCRequest& request)
 UniValue setban(const JSONRPCRequest& request)
 {
     std::string strCommand;
-    if (request.params.size() >= 2)
+    if (!request.params[1].isNull())
         strCommand = request.params[1].get_str();
     if (request.fHelp || request.params.size() < 2 ||
         (strCommand != "add" && strCommand != "remove"))
@@ -534,11 +534,11 @@ UniValue setban(const JSONRPCRequest& request)
             throw JSONRPCError(RPC_CLIENT_NODE_ALREADY_ADDED, "Error: IP/Subnet already banned");
 
         int64_t banTime = 0; //use standard bantime if not specified
-        if (request.params.size() >= 3 && !request.params[2].isNull())
+        if (!request.params[2].isNull())
             banTime = request.params[2].get_int64();
 
         bool absolute = false;
-        if (request.params.size() == 4 && request.params[3].isTrue())
+        if (request.params[3].isTrue())
             absolute = true;
 
         isSubnet ? g_connman->Ban(subNet, BanReasonManuallyAdded, banTime, absolute) : g_connman->Ban(netAddr, BanReasonManuallyAdded, banTime, absolute);
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 55e4746827..934576a391 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -336,14 +336,14 @@ UniValue createrawtransaction(const JSONRPCRequest& request)
 
     CMutableTransaction rawTx;
 
-    if (request.params.size() > 2 && !request.params[2].isNull()) {
+    if (!request.params[2].isNull()) {
         int64_t nLockTime = request.params[2].get_int64();
         if (nLockTime < 0 || nLockTime > std::numeric_limits<uint32_t>::max())
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, locktime out of range");
         rawTx.nLockTime = nLockTime;
     }
 
-    bool rbfOptIn = request.params.size() > 3 ? request.params[3].isTrue() : false;
+    bool rbfOptIn = request.params[3].isTrue();
 
     for (unsigned int idx = 0; idx < inputs.size(); idx++) {
         const UniValue& input = inputs[idx];
@@ -732,7 +732,7 @@ UniValue signrawtransaction(const JSONRPCRequest& request)
 
     bool fGivenKeys = false;
     CBasicKeyStore tempKeystore;
-    if (request.params.size() > 2 && !request.params[2].isNull()) {
+    if (!request.params[2].isNull()) {
         fGivenKeys = true;
         UniValue keys = request.params[2].get_array();
         for (unsigned int idx = 0; idx < keys.size(); idx++) {
@@ -754,7 +754,7 @@ UniValue signrawtransaction(const JSONRPCRequest& request)
 #endif
 
     // Add previous txouts given in the RPC call:
-    if (request.params.size() > 1 && !request.params[1].isNull()) {
+    if (!request.params[1].isNull()) {
         UniValue prevTxs = request.params[1].get_array();
         for (unsigned int idx = 0; idx < prevTxs.size(); idx++) {
             const UniValue& p = prevTxs[idx];
@@ -825,7 +825,7 @@ UniValue signrawtransaction(const JSONRPCRequest& request)
 #endif
 
     int nHashType = SIGHASH_ALL;
-    if (request.params.size() > 3 && !request.params[3].isNull()) {
+    if (!request.params[3].isNull()) {
         static std::map<std::string, int> mapSigHashValues = {
             {std::string("ALL"), int(SIGHASH_ALL)},
             {std::string("ALL|ANYONECANPAY"), int(SIGHASH_ALL|SIGHASH_ANYONECANPAY)},
@@ -919,7 +919,7 @@ UniValue sendrawtransaction(const JSONRPCRequest& request)
     const uint256& hashTx = tx->GetHash();
 
     CAmount nMaxRawTxFee = maxTxFee;
-    if (request.params.size() > 1 && request.params[1].get_bool())
+    if (!request.params[1].isNull() && request.params[1].get_bool())
         nMaxRawTxFee = 0;
 
     CCoinsViewCache &view = *pcoinsTip;
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 3fd8879ed4..513f7b32a5 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -280,7 +280,7 @@ UniValue setaccount(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address");
 
     std::string strAccount;
-    if (request.params.size() > 1)
+    if (!request.params[1].isNull())
         strAccount = AccountFromValue(request.params[1]);
 
     // Only add the account if the address is yours.
@@ -462,26 +462,26 @@ UniValue sendtoaddress(const JSONRPCRequest& request)
 
     // Wallet comments
     CWalletTx wtx;
-    if (request.params.size() > 2 && !request.params[2].isNull() && !request.params[2].get_str().empty())
+    if (!request.params[2].isNull() && !request.params[2].get_str().empty())
         wtx.mapValue["comment"] = request.params[2].get_str();
-    if (request.params.size() > 3 && !request.params[3].isNull() && !request.params[3].get_str().empty())
+    if (!request.params[3].isNull() && !request.params[3].get_str().empty())
         wtx.mapValue["to"]      = request.params[3].get_str();
 
     bool fSubtractFeeFromAmount = false;
-    if (request.params.size() > 4 && !request.params[4].isNull()) {
+    if (!request.params[4].isNull()) {
         fSubtractFeeFromAmount = request.params[4].get_bool();
     }
 
     CCoinControl coin_control;
-    if (request.params.size() > 5 && !request.params[5].isNull()) {
+    if (!request.params[5].isNull()) {
         coin_control.signalRbf = request.params[5].get_bool();
     }
 
-    if (request.params.size() > 6 && !request.params[6].isNull()) {
+    if (!request.params[6].isNull()) {
         coin_control.m_confirm_target = ParseConfirmTarget(request.params[6]);
     }
 
-    if (request.params.size() > 7 && !request.params[7].isNull()) {
+    if (!request.params[7].isNull()) {
         if (!FeeModeFromString(request.params[7].get_str(), coin_control.m_fee_mode)) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid estimate_mode parameter");
         }
@@ -768,18 +768,31 @@ UniValue getbalance(const JSONRPCRequest& request)
 
     LOCK2(cs_main, pwallet->cs_wallet);
 
-    if (request.params.size() == 0)
-        return  ValueFromAmount(pwallet->GetBalance());
+    const UniValue& account_value = request.params[0];
+    const UniValue& minconf = request.params[1];
+    const UniValue& include_watchonly = request.params[2];
+
+    if (account_value.isNull()) {
+        if (!minconf.isNull()) {
+            throw JSONRPCError(RPC_INVALID_PARAMETER,
+                "getbalance minconf option is only currently supported if an account is specified");
+        }
+        if (!include_watchonly.isNull()) {
+            throw JSONRPCError(RPC_INVALID_PARAMETER,
+                "getbalance include_watchonly option is only currently supported if an account is specified");
+        }
+        return ValueFromAmount(pwallet->GetBalance());
+    }
 
-    const std::string& account_param = request.params[0].get_str();
+    const std::string& account_param = account_value.get_str();
     const std::string* account = account_param != "*" ? &account_param : nullptr;
 
     int nMinDepth = 1;
-    if (!request.params[1].isNull())
-        nMinDepth = request.params[1].get_int();
+    if (!minconf.isNull())
+        nMinDepth = minconf.get_int();
     isminefilter filter = ISMINE_SPENDABLE;
-    if(!request.params[2].isNull())
-        if(request.params[2].get_bool())
+    if(!include_watchonly.isNull())
+        if(include_watchonly.get_bool())
             filter = filter | ISMINE_WATCH_ONLY;
 
     return ValueFromAmount(pwallet->GetLegacyBalance(filter, nMinDepth, account));
@@ -838,11 +851,11 @@ UniValue movecmd(const JSONRPCRequest& request)
     CAmount nAmount = AmountFromValue(request.params[2]);
     if (nAmount <= 0)
         throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount for send");
-    if (request.params.size() > 3)
+    if (!request.params[3].isNull())
         // unused parameter, used to be nMinDepth, keep type-checking it though
         (void)request.params[3].get_int();
     std::string strComment;
-    if (request.params.size() > 4)
+    if (!request.params[4].isNull())
         strComment = request.params[4].get_str();
 
     if (!pwallet->AccountMove(strFrom, strTo, nAmount, strComment)) {
@@ -899,14 +912,14 @@ UniValue sendfrom(const JSONRPCRequest& request)
     if (nAmount <= 0)
         throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount for send");
     int nMinDepth = 1;
-    if (request.params.size() > 3)
+    if (!request.params[3].isNull())
         nMinDepth = request.params[3].get_int();
 
     CWalletTx wtx;
     wtx.strFromAccount = strAccount;
-    if (request.params.size() > 4 && !request.params[4].isNull() && !request.params[4].get_str().empty())
+    if (!request.params[4].isNull() && !request.params[4].get_str().empty())
         wtx.mapValue["comment"] = request.params[4].get_str();
-    if (request.params.size() > 5 && !request.params[5].isNull() && !request.params[5].get_str().empty())
+    if (!request.params[5].isNull() && !request.params[5].get_str().empty())
         wtx.mapValue["to"]      = request.params[5].get_str();
 
     EnsureWalletIsUnlocked(pwallet);
@@ -986,23 +999,23 @@ UniValue sendmany(const JSONRPCRequest& request)
 
     CWalletTx wtx;
     wtx.strFromAccount = strAccount;
-    if (request.params.size() > 3 && !request.params[3].isNull() && !request.params[3].get_str().empty())
+    if (!request.params[3].isNull() && !request.params[3].get_str().empty())
         wtx.mapValue["comment"] = request.params[3].get_str();
 
     UniValue subtractFeeFromAmount(UniValue::VARR);
-    if (request.params.size() > 4 && !request.params[4].isNull())
+    if (!request.params[4].isNull())
         subtractFeeFromAmount = request.params[4].get_array();
 
     CCoinControl coin_control;
-    if (request.params.size() > 5 && !request.params[5].isNull()) {
+    if (!request.params[5].isNull()) {
         coin_control.signalRbf = request.params[5].get_bool();
     }
 
-    if (request.params.size() > 6 && !request.params[6].isNull()) {
+    if (!request.params[6].isNull()) {
         coin_control.m_confirm_target = ParseConfirmTarget(request.params[6]);
     }
 
-    if (request.params.size() > 7 && !request.params[7].isNull()) {
+    if (!request.params[7].isNull()) {
         if (!FeeModeFromString(request.params[7].get_str(), coin_control.m_fee_mode)) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid estimate_mode parameter");
         }
@@ -1105,7 +1118,7 @@ UniValue addmultisigaddress(const JSONRPCRequest& request)
     LOCK2(cs_main, pwallet->cs_wallet);
 
     std::string strAccount;
-    if (request.params.size() > 2)
+    if (!request.params[2].isNull())
         strAccount = AccountFromValue(request.params[2]);
 
     // Construct using pay-to-script-hash:
@@ -1711,10 +1724,10 @@ UniValue listaccounts(const JSONRPCRequest& request)
     LOCK2(cs_main, pwallet->cs_wallet);
 
     int nMinDepth = 1;
-    if (request.params.size() > 0)
+    if (!request.params[0].isNull())
         nMinDepth = request.params[0].get_int();
     isminefilter includeWatchonly = ISMINE_SPENDABLE;
-    if(request.params.size() > 1)
+    if(!request.params[1].isNull())
         if(request.params[1].get_bool())
             includeWatchonly = includeWatchonly | ISMINE_WATCH_ONLY;
 
@@ -2363,19 +2376,18 @@ UniValue lockunspent(const JSONRPCRequest& request)
 
     LOCK2(cs_main, pwallet->cs_wallet);
 
-    if (request.params.size() == 1)
-        RPCTypeCheck(request.params, {UniValue::VBOOL});
-    else
-        RPCTypeCheck(request.params, {UniValue::VBOOL, UniValue::VARR});
+    RPCTypeCheckArgument(request.params[0], UniValue::VBOOL);
 
     bool fUnlock = request.params[0].get_bool();
 
-    if (request.params.size() == 1) {
+    if (request.params[1].isNull()) {
         if (fUnlock)
             pwallet->UnlockAllCoins();
         return true;
     }
 
+    RPCTypeCheckArgument(request.params[1], UniValue::VARR);
+
     UniValue outputs = request.params[1].get_array();
     for (unsigned int idx = 0; idx < outputs.size(); idx++) {
         const UniValue& output = outputs[idx];
@@ -2672,19 +2684,19 @@ UniValue listunspent(const JSONRPCRequest& request)
         );
 
     int nMinDepth = 1;
-    if (request.params.size() > 0 && !request.params[0].isNull()) {
+    if (!request.params[0].isNull()) {
         RPCTypeCheckArgument(request.params[0], UniValue::VNUM);
         nMinDepth = request.params[0].get_int();
     }
 
     int nMaxDepth = 9999999;
-    if (request.params.size() > 1 && !request.params[1].isNull()) {
+    if (!request.params[1].isNull()) {
         RPCTypeCheckArgument(request.params[1], UniValue::VNUM);
         nMaxDepth = request.params[1].get_int();
     }
 
     std::set<CBitcoinAddress> setAddress;
-    if (request.params.size() > 2 && !request.params[2].isNull()) {
+    if (!request.params[2].isNull()) {
         RPCTypeCheckArgument(request.params[2], UniValue::VARR);
         UniValue inputs = request.params[2].get_array();
         for (unsigned int idx = 0; idx < inputs.size(); idx++) {
@@ -2699,7 +2711,7 @@ UniValue listunspent(const JSONRPCRequest& request)
     }
 
     bool include_unsafe = true;
-    if (request.params.size() > 3 && !request.params[3].isNull()) {
+    if (!request.params[3].isNull()) {
         RPCTypeCheckArgument(request.params[3], UniValue::VBOOL);
         include_unsafe = request.params[3].get_bool();
     }
@@ -3114,7 +3126,7 @@ UniValue generate(const JSONRPCRequest& request)
 
     int num_generate = request.params[0].get_int();
     uint64_t max_tries = 1000000;
-    if (request.params.size() > 1 && !request.params[1].isNull()) {
+    if (!request.params[1].isNull()) {
         max_tries = request.params[1].get_int();
     }