Merge #15401: rpc: Actually throw help when passed invalid number of params

fa4ce7038d444defe0b98a30097174c278054a33 rpc: Actually throw help when passed invalid number of params (MarcoFalke)
fa05626ca7a0fe896ac554c79eaea4c36acdf861 rpc: Add RPCHelpMan::IsValidNumArgs() (MarcoFalke)

Pull request description:

  Can be tested by

  * running the included test against an old binary (compiled without this patch)
  * calling `setban 1 "add" 3 4 5 6 7 8 9 0` in the gui

Tree-SHA512: aa6a25bbe6f40722913ea292252a62a4012c964eed9f4035335a2e2d13be98eb60f368e8a3251a104a26a62c08b2cb926b06e5ab1418ef1cf4abdd71d87c2919

1 files changed, 22 insertions, 7 deletions

diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index 1eec916abf..86695bc1a5 100644
--- a/src/rpc/util.cpp
+++ b/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.
 
@@ -314,6 +314,17 @@ 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;
@@ -322,12 +333,7 @@ std::string RPCHelpMan::ToString() const
     ret += m_name;
     bool was_optional{false};
     for (const auto& arg : m_args) {
-        bool optional;
-        if (arg.m_fallback.which() == 1) {
-            optional = true;
-        } else {
-            optional = RPCArg::Optional::NO != boost::get<RPCArg::Optional>(arg.m_fallback);
-        }
+        const bool optional = arg.IsOptional();
         ret += " ";
         if (optional) {
             if (!was_optional) ret += "( ";
@@ -369,6 +375,15 @@ 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;