rpc: Add RPCHelpMan for machine-generated help

Author: MarcoFalke

src/rpc/rawtransaction.cpp

@@ -206,7 +206,16 @@ static UniValue gettxoutproof(const JSONRPCRequest& request)
 {
     if (request.fHelp || (request.params.size() != 1 && request.params.size() != 2))
         throw std::runtime_error(
-            "gettxoutproof [\"txid\",...] ( blockhash )\n"
+            RPCHelpMan{"gettxoutproof",
+                {
+                    {"txids", RPCArg::Type::ARR,
+                        {
+                            {"txid", RPCArg::Type::STR_HEX, false},
+                        },
+                        false},
+                    {"blockhash", RPCArg::Type::STR_HEX, true},
+                }}
+                .ToString() +
             "\nReturns a hex-encoded proof that \"txid\" was included in a block.\n"
             "\nNOTE: By default this function only works sometimes. This is when there is an\n"
             "unspent output in the utxo for this transaction. To make it always work,\n"
@@ -673,10 +682,17 @@ static void TxInErrorToJSON(const CTxIn& txin, UniValue& vErrorsRet, const std::
 
 static UniValue combinerawtransaction(const JSONRPCRequest& request)
 {
-
     if (request.fHelp || request.params.size() != 1)
         throw std::runtime_error(
-            "combinerawtransaction [\"hexstring\",...]\n"
+            RPCHelpMan{"combinerawtransaction",
+                {
+                    {"txs", RPCArg::Type::ARR,
+                        {
+                            {"hexstring", RPCArg::Type::STR_HEX, false},
+                        },
+                        false},
+                }}
+                .ToString() +
             "\nCombine multiple partially signed transactions into one transaction.\n"
             "The combined transaction may be another partially signed transaction or a \n"
             "fully signed transaction."
@@ -899,7 +915,30 @@ static UniValue signrawtransactionwithkey(const JSONRPCRequest& request)
 {
     if (request.fHelp || request.params.size() < 2 || request.params.size() > 4)
         throw std::runtime_error(
-            "signrawtransactionwithkey \"hexstring\" [\"privatekey1\",...] ( [{\"txid\":\"id\",\"vout\":n,\"scriptPubKey\":\"hex\",\"redeemScript\":\"hex\"},...] sighashtype )\n"
+            RPCHelpMan{"signrawtransactionwithkey",
+                {
+                    {"hexstring", RPCArg::Type::STR, false},
+                    {"privkyes", RPCArg::Type::ARR,
+                        {
+                            {"privatekey", RPCArg::Type::STR_HEX, false},
+                        },
+                        false},
+                    {"prevtxs", RPCArg::Type::ARR,
+                        {
+                            {"", RPCArg::Type::OBJ,
+                                {
+                                    {"txid", RPCArg::Type::STR_HEX, false},
+                                    {"vout", RPCArg::Type::NUM, false},
+                                    {"scriptPubKey", RPCArg::Type::STR_HEX, false},
+                                    {"redeemScript", RPCArg::Type::STR_HEX, false},
+                                    {"amount", RPCArg::Type::AMOUNT, false},
+                                },
+                                true},
+                        },
+                        true},
+                    {"sighashtype", RPCArg::Type::STR, true},
+                }}
+                .ToString() +
             "\nSign inputs for raw transaction (serialized, hex-encoded).\n"
             "The second argument is an array of base58-encoded private\n"
             "keys that will be the only keys used to sign the transaction.\n"
@@ -1454,7 +1493,15 @@ UniValue combinepsbt(const JSONRPCRequest& request)
 {
     if (request.fHelp || request.params.size() != 1)
         throw std::runtime_error(
-            "combinepsbt [\"psbt\",...]\n"
+            RPCHelpMan{"combinepsbt",
+                {
+                    {"txs", RPCArg::Type::ARR,
+                        {
+                            {"psbt", RPCArg::Type::STR_HEX, false},
+                        },
+                        false},
+                }}
+                .ToString() +
             "\nCombine multiple partially signed Bitcoin transactions into one transaction.\n"
             "Implements the Combiner role.\n"
             "\nArguments:\n"
@@ -1570,7 +1617,37 @@ UniValue createpsbt(const JSONRPCRequest& request)
 {
     if (request.fHelp || request.params.size() < 2 || request.params.size() > 4)
         throw std::runtime_error(
-                            "createpsbt [{\"txid\":\"id\",\"vout\":n},...] [{\"address\":amount},{\"data\":\"hex\"},...] ( locktime ) ( replaceable )\n"
+            RPCHelpMan{"createpsbt",
+                {
+                    {"inputs", RPCArg::Type::ARR,
+                        {
+                            {"", RPCArg::Type::OBJ,
+                                {
+                                    {"txid", RPCArg::Type::STR_HEX, false},
+                                    {"vout", RPCArg::Type::NUM, false},
+                                    {"sequence", RPCArg::Type::NUM, true},
+                                },
+                                false},
+                        },
+                        false},
+                    {"outputs", RPCArg::Type::ARR,
+                        {
+                            {"", RPCArg::Type::OBJ,
+                                {
+                                    {"address", RPCArg::Type::AMOUNT, false},
+                                },
+                                true},
+                            {"", RPCArg::Type::OBJ,
+                                {
+                                    {"data", RPCArg::Type::STR_HEX, false},
+                                },
+                                true},
+                        },
+                        false},
+                    {"locktime", RPCArg::Type::NUM, true},
+                    {"replaceable", RPCArg::Type::BOOL, true},
+                }}
+                .ToString() +
                             "\nCreates a transaction in the Partially Signed Transaction format.\n"
                             "Implements the Creator role.\n"
                             "\nArguments:\n"

src/rpc/util.cpp

@@ -128,3 +128,95 @@ UniValue DescribeAddress(const CTxDestination& dest)
 {
     return boost::apply_visitor(DescribeAddressVisitor(), dest);
 }
+
+std::string RPCHelpMan::ToString() const
+{
+    std::string ret;
+
+    ret += m_name;
+    bool is_optional{false};
+    for (const auto& arg : m_args) {
+        ret += " ";
+        if (arg.m_optional) {
+            if (!is_optional) ret += "( ";
+            is_optional = true;
+        } else {
+            // Currently we still support unnamed arguments, so any argument following an optional argument must also be optional
+            // If support for positional arguments is deprecated in the future, remove this line
+            assert(!is_optional);
+        }
+        ret += arg.ToString();
+    }
+    if (is_optional) ret += " )";
+    ret += "\n";
+
+    return ret;
+}
+
+std::string RPCArg::ToStringObj() const
+{
+    std::string res = "\"" + m_name + "\":";
+    switch (m_type) {
+    case Type::STR:
+        return res + "\"str\"";
+    case Type::STR_HEX:
+        return res + "\"hex\"";
+    case Type::NUM:
+        return res + "n";
+    case Type::AMOUNT:
+        return res + "amount";
+    case Type::BOOL:
+        return res + "bool";
+    case Type::ARR:
+        res += "[";
+        for (const auto& i : m_inner) {
+            res += i.ToString() + ",";
+        }
+        return res + "...]";
+    case Type::OBJ:
+    case Type::OBJ_USER_KEYS:
+        // Currently unused, so avoid writing dead code
+        assert(false);
+
+        // no default case, so the compiler can warn about missing cases
+    }
+    assert(false);
+}
+
+std::string RPCArg::ToString() const
+{
+    switch (m_type) {
+    case Type::STR_HEX:
+    case Type::STR: {
+        return "\"" + m_name + "\"";
+    }
+    case Type::NUM:
+    case Type::AMOUNT:
+    case Type::BOOL: {
+        return m_name;
+    }
+    case Type::OBJ:
+    case Type::OBJ_USER_KEYS: {
+        std::string res;
+        for (size_t i = 0; i < m_inner.size();) {
+            res += m_inner[i].ToStringObj();
+            if (++i < m_inner.size()) res += ",";
+        }
+        if (m_type == Type::OBJ) {
+            return "{" + res + "}";
+        } else {
+            return "{" + res + ",...}";
+        }
+    }
+    case Type::ARR: {
+        std::string res;
+        for (const auto& i : m_inner) {
+            res += i.ToString() + ",";
+        }
+        return "[" + res + "...]";
+    }
+
+        // no default case, so the compiler can warn about missing cases
+    }
+    assert(false);
+}

src/rpc/util.h

@@ -30,4 +30,53 @@ CScript CreateMultisigRedeemscript(const int required, const std::vector<CPubKey
 
 UniValue DescribeAddress(const CTxDestination& dest);
 
+struct RPCArg {
+    enum class Type {
+        OBJ,
+        ARR,
+        STR,
+        NUM,
+        BOOL,
+        OBJ_USER_KEYS, //!< Special type where the user must set the keys e.g. to define multiple addresses; as opposed to e.g. an options object where the keys are predefined
+        AMOUNT,        //!< Special type representing a floating point amount (can be either NUM or STR)
+        STR_HEX,       //!< Special type that is a STR with only hex chars
+    };
+    const std::string m_name; //!< The name of the arg (can be empty for inner args)
+    const Type m_type;
+    const std::vector<RPCArg> m_inner; //!< Only used for arrays or dicts
+    const bool m_optional;
+
+    RPCArg(const std::string& name, const Type& type, const bool optional)
+        : m_name{name}, m_type{type}, m_optional{optional}
+    {
+        assert(type != Type::ARR && type != Type::OBJ);
+    }
+
+    RPCArg(const std::string& name, const Type& type, const std::vector<RPCArg>& inner, const bool optional)
+        : m_name{name}, m_type{type}, m_inner{inner}, m_optional{optional}
+    {
+        assert(type == Type::ARR || type == Type::OBJ);
+    }
+
+    std::string ToString() const;
+
+private:
+    std::string ToStringObj() const;
+};
+
+class RPCHelpMan
+{
+public:
+    RPCHelpMan(const std::string& name, const std::vector<RPCArg>& args)
+        : m_name{name}, m_args{args}
+    {
+    }
+
+    std::string ToString() const;
+
+private:
+    const std::string m_name;
+    const std::vector<RPCArg> m_args;
+};
+
 #endif // BITCOIN_RPC_UTIL_H