rpc: Add RPCHelpMan for machine-generated help

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);
+}