rpc: Add RPCHelpMan::IsValidNumArgs()

src/rpc/util.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2017-2018 The Bitcoin Core developers
+// Copyright (c) 2017-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -315,6 +315,17 @@ std::string RPCExamples::ToDescriptionString() const
     return m_examples.empty() ? m_examples : "\nExamples:\n" + m_examples;
 }
 
+bool RPCHelpMan::IsValidNumArgs(size_t num_args) const
+{
+    size_t num_required_args = 0;
+    for (size_t n = m_args.size(); n > 0; --n) {
+        if (!m_args.at(n - 1).IsOptional()) {
+            num_required_args = n;
+            break;
+        }
+    }
+    return num_required_args <= num_args && num_args <= m_args.size();
+}
 std::string RPCHelpMan::ToString() const
 {
     std::string ret;
@@ -323,12 +334,7 @@ std::string RPCHelpMan::ToString() const
     ret += m_name;
     bool was_optional{false};
     for (const auto& arg : m_args) {
-        bool optional;
+        const bool optional = arg.IsOptional();
-        if (arg.m_fallback.which() == 1) {
-            optional = true;
-        } else {
-            optional = RPCArg::Optional::NO != boost::get<RPCArg::Optional>(arg.m_fallback);
-        }
         ret += " ";
         if (optional) {
             if (!was_optional) ret += "( ";
@@ -370,6 +376,15 @@ std::string RPCHelpMan::ToString() const
     return ret;
 }
 
+bool RPCArg::IsOptional() const
+{
+    if (m_fallback.which() == 1) {
+        return true;
+    } else {
+        return RPCArg::Optional::NO != boost::get<RPCArg::Optional>(m_fallback);
+    }
+}
+
 std::string RPCArg::ToDescriptionString() const
 {
     std::string ret;

src/rpc/util.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2017-2018 The Bitcoin Core developers
+// Copyright (c) 2017-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -53,7 +53,7 @@ struct RPCArg {
         /** Required arg */
         NO,
         /**
-         * Optinal arg that is a named argument and has a default value of
+         * Optional arg that is a named argument and has a default value of
          * `null`. When possible, the default value should be specified.
          */
         OMITTED_NAMED_ARG,
@@ -110,6 +110,8 @@ struct RPCArg {
         assert(type == Type::ARR || type == Type::OBJ);
     }
 
+    bool IsOptional() const;
+
     /**
      * Return the type string of the argument.
      * Set oneline to allow it to be overridden by a custom oneline type string (m_oneline_description).
@@ -185,6 +187,8 @@ public:
     RPCHelpMan(std::string name, std::string description, std::vector<RPCArg> args, RPCResults results, RPCExamples examples);
 
     std::string ToString() const;
+    /** If the supplied number of args is neither too small nor too high */
+    bool IsValidNumArgs(size_t num_args) const;
 
 private:
     const std::string m_name;