Merge bitcoin#15899: rpc: Document iswitness flag and fix bug in conv…

…erttopsbt

fa499b5 rpc: bugfix: Properly use iswitness in converttopsbt (MarcoFalke)
fa5c5cd rpc: Switch touched RPCs to IsValidNumArgs (MarcoFalke)

Pull request description:

  When a serialized transaction has inputs, there is no risk in only trying to deserialize it with witness allowed. (This is how all transactions from p2p are deserialized.) In fact, it would avoid a common issue where a transaction with inputs can be deserialized in two ways:
  * Fixes bitcoin#12989
  * Fixes bitcoin#15872
  * Fixes bitcoin#15701
  * Fixes bitcoin#13738
  * ...

  When a serialized transaction has no inputs, there is no risk in only trying to deserialze it with witness disallowed. (A transaction without inputs can't have corresponding witness data)

ACKs for commit fa499b:
  meshcollider:
    utACK bitcoin@fa499b5
  ryanofsky:
    utACK fa499b5. Changes since last review: consolidating commits and making iswitness documentation the same across methods.
  PastaPastaPasta:
    utACK fa499b5

Tree-SHA512: a64423a3131f3f0222a40da557c8b590c9ff01b45bcd40796f77a1a64ae74c6680a6be9d01ece95c492dfbcc7e2810409d2c2b336c2894af00bb213972fc85c6

src/rpc/rawtransaction.cpp

@@ -471,9 +471,7 @@ static UniValue createrawtransaction(const JSONRPCRequest& request)
 
 static UniValue decoderawtransaction(const JSONRPCRequest& request)
 {
-    if (request.fHelp || request.params.size() != 1)
-        throw std::runtime_error(
-            RPCHelpMan{"decoderawtransaction",
+                const RPCHelpMan help{"decoderawtransaction",
                 "\nReturn a JSON object representing the serialized, hex-encoded transaction.\n",
                 {
                     {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The transaction hex string"},
@@ -522,7 +520,8 @@ static UniValue decoderawtransaction(const JSONRPCRequest& request)
                     HelpExampleCli("decoderawtransaction", "\"hexstring\"")
             + HelpExampleRpc("decoderawtransaction", "\"hexstring\"")
                 },
-            }.ToString());
+    };
+
 
     RPCTypeCheck(request.params, {UniValue::VSTR});
 
@@ -1350,14 +1349,12 @@ UniValue createpsbt(const JSONRPCRequest& request)
 
 UniValue converttopsbt(const JSONRPCRequest& request)
 {
-    if (request.fHelp || request.params.size() < 1 || request.params.size() > 3)
-        throw std::runtime_error(
-            RPCHelpMan{"converttopsbt",
+    const RPCHelpMan help{"converttopsbt",
                 "\nConverts a network serialized transaction to a PSBT. This should be used only with createrawtransaction and fundrawtransaction\n"
                 "createpsbt and walletcreatefundedpsbt should be used for new applications.\n",
                 {
                     {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The hex string of a raw transaction"},
-                    {"permitsigdata", RPCArg::Type::BOOL, /* default */ "false", "If true, any signatures in the input will be discarded and conversion.\n"
+                    {"permitsigdata", RPCArg::Type::BOOL, /* default */ "false", "If true, any signatures in the input will be discarded and conversion\n"
                             "                              will continue. If false, RPC will fail if any signatures are present."},
                 },
                 RPCResult{
@@ -1369,7 +1366,7 @@ UniValue converttopsbt(const JSONRPCRequest& request)
                             "\nConvert the transaction to a PSBT\n"
                             + HelpExampleCli("converttopsbt", "\"rawtransaction\"")
                 },
-            }.ToString());
+    };
 
 
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VBOOL, UniValue::VBOOL}, true);

src/wallet/rpcwallet.cpp

@@ -3332,9 +3332,7 @@ static UniValue fundrawtransaction(const JSONRPCRequest& request)
         return NullUniValue;
     }
 
-    if (request.fHelp || request.params.size() < 1 || request.params.size() > 3)
-        throw std::runtime_error(
-            RPCHelpMan{"fundrawtransaction",
+    const RPCHelpMan help{"fundrawtransaction",
                 "\nAdd inputs to a transaction until it has enough in value to meet its out value.\n"
                 "This will not modify existing inputs, and will add at most one change output to the outputs.\n"
                 "No existing outputs will be modified unless \"subtractFeeFromOutputs\" is specified.\n"
@@ -3388,7 +3386,8 @@ static UniValue fundrawtransaction(const JSONRPCRequest& request)
                             "\nSend the transaction\n"
                             + HelpExampleCli("sendrawtransaction", "\"signedtransactionhex\"")
                                 },
-                            }.ToString());
+    };
+
 
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValueType(), UniValue::VBOOL});