Merge #21035: Remove pointer cast in CRPCTable::dumpArgMap

9048c58e10841d9e1d709c0a325dd14684cec325 Remove pointer cast in CRPCTable::dumpArgMap (Russell Yanofsky)
14f3d9b908ed9e78997bfaad3d8a06357a89d46e refactor: Add RPC server ExecuteCommands function (Russell Yanofsky)
6158a6d3978a18d5ac4166ca2f59056d8ef71c3d refactor: Replace JSONRPCRequest fHelp field with mode field (Russell Yanofsky)

Pull request description:

  This change is needed to fix the `rpc_help.py` test failing in #10102: https://cirrus-ci.com/task/5469433013469184?command=ci#L2275

  The [`CRPCTable::dumpArgMap`](https://github.com/bitcoin/bitcoin/blob/16b784d953365bb2d7ae65acd2b20a79ef8ba7b6/src/rpc/server.cpp#L492) method currently works by casting RPC `unique_id` integer field to a function pointer, and then calling it. The `unique_id` field wasn't supposed to be used this way (it's meant to be used to detect RPC aliases) and as a result, this code segfaults in the `rpc_help.py` test in multiprocess PR #10102 because wallet RPC functions aren't directly accessible from the node process.

  Fix this by adding a new `GET_ARGS` RPC request mode to retrieve argument information similar to the way the `GET_HELP` mode retrieves help information.

  ---

  This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10).

ACKs for top commit:
  MarcoFalke:
    re-ACK 9048c58e10841d9e1d709c0a325dd14684cec325 👑

Tree-SHA512: cd1a01c1daa5bde2c2455b63548371ee4cf39688313969ad2016d9a0fd4344102e3fd43034058f253364518e9632d57cf21abffad0d6a2c0c94b7a6921cbe615

5 files changed, 48 insertions, 32 deletions

diff --git a/src/rpc/request.h b/src/rpc/request.h
index de3a4ae840..27d06f3c92 100644
--- a/src/rpc/request.h
+++ b/src/rpc/request.h
@@ -34,19 +34,19 @@ public:
     UniValue id;
     std::string strMethod;
     UniValue params;
-    bool fHelp;
+    enum Mode { EXECUTE, GET_HELP, GET_ARGS } mode = EXECUTE;
     std::string URI;
     std::string authUser;
     std::string peerAddr;
     const util::Ref& context;
 
-    explicit JSONRPCRequest(const util::Ref& context) : id(NullUniValue), params(NullUniValue), fHelp(false), context(context) {}
+    explicit JSONRPCRequest(const util::Ref& context) : id(NullUniValue), params(NullUniValue), context(context) {}
 
     //! Initializes request information from another request object and the
     //! given context. The implementation should be updated if any members are
     //! added or removed above.
     JSONRPCRequest(const JSONRPCRequest& other, const util::Ref& context)
-        : id(other.id), strMethod(other.strMethod), params(other.params), fHelp(other.fHelp), URI(other.URI),
+        : id(other.id), strMethod(other.strMethod), params(other.params), mode(other.mode), URI(other.URI),
           authUser(other.authUser), peerAddr(other.peerAddr), context(context)
     {
     }
diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
index 9a9b3713f3..39938f4eb9 100644
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -88,7 +88,7 @@ std::string CRPCTable::help(const std::string& strCommand, const JSONRPCRequest&
     sort(vCommands.begin(), vCommands.end());
 
     JSONRPCRequest jreq(helpreq);
-    jreq.fHelp = true;
+    jreq.mode = JSONRPCRequest::GET_HELP;
     jreq.params = UniValue();
 
     for (const std::pair<std::string, const CRPCCommand*>& command : vCommands)
@@ -149,7 +149,7 @@ static RPCHelpMan help()
     }
     if (strCommand == "dump_all_command_conversions") {
         // Used for testing only, undocumented
-        return tableRPC.dumpArgMap();
+        return tableRPC.dumpArgMap(jsonRequest);
     }
 
     return tableRPC.help(strCommand, jsonRequest);
@@ -437,6 +437,16 @@ static inline JSONRPCRequest transformNamedArguments(const JSONRPCRequest& in, c
     return out;
 }
 
+static bool ExecuteCommands(const std::vector<const CRPCCommand*>& commands, const JSONRPCRequest& request, UniValue& result)
+{
+    for (const auto& command : commands) {
+        if (ExecuteCommand(*command, request, result, &command == &commands.back())) {
+            return true;
+        }
+    }
+    return false;
+}
+
 UniValue CRPCTable::execute(const JSONRPCRequest &request) const
 {
     // Return immediately if in warmup
@@ -450,10 +460,8 @@ UniValue CRPCTable::execute(const JSONRPCRequest &request) const
     auto it = mapCommands.find(request.strMethod);
     if (it != mapCommands.end()) {
         UniValue result;
-        for (const auto& command : it->second) {
-            if (ExecuteCommand(*command, request, result, &command == &it->second.back())) {
-                return result;
-            }
+        if (ExecuteCommands(it->second, request, result)) {
+            return result;
         }
     }
     throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Method not found");
@@ -484,13 +492,18 @@ std::vector<std::string> CRPCTable::listCommands() const
     return commandList;
 }
 
-UniValue CRPCTable::dumpArgMap() const
+UniValue CRPCTable::dumpArgMap(const JSONRPCRequest& args_request) const
 {
+    JSONRPCRequest request(args_request);
+    request.mode = JSONRPCRequest::GET_ARGS;
+
     UniValue ret{UniValue::VARR};
     for (const auto& cmd : mapCommands) {
-        for (const auto& c : cmd.second) {
-            const auto help = RpcMethodFnType(c->unique_id)();
-            help.AppendArgMap(ret);
+        UniValue result;
+        if (ExecuteCommands(cmd.second, request, result)) {
+            for (const auto& values : result.getValues()) {
+                ret.push_back(values);
+            }
         }
     }
     return ret;
diff --git a/src/rpc/server.h b/src/rpc/server.h
index fe5a791e1e..03967020c2 100644
--- a/src/rpc/server.h
+++ b/src/rpc/server.h
@@ -148,7 +148,7 @@ public:
     /**
      * Return all named arguments that need to be converted by the client from string to another JSON type
      */
-    UniValue dumpArgMap() const;
+    UniValue dumpArgMap(const JSONRPCRequest& request) const;
 
     /**
      * Appends a CRPCCommand to the dispatch table.
diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index e890c0108a..44e58cb75f 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -459,6 +459,21 @@ std::string RPCExamples::ToDescriptionString() const
     return m_examples.empty() ? m_examples : "\nExamples:\n" + m_examples;
 }
 
+UniValue RPCHelpMan::HandleRequest(const JSONRPCRequest& request)
+{
+    if (request.mode == JSONRPCRequest::GET_ARGS) {
+        return GetArgMap();
+    }
+    /*
+     * Check if the given request is valid according to this command or if
+     * the user is asking for help information, and throw help when appropriate.
+     */
+    if (request.mode == JSONRPCRequest::GET_HELP || !IsValidNumArgs(request.params.size())) {
+        throw std::runtime_error(ToString());
+    }
+    return m_fun(*this, request);
+}
+
 bool RPCHelpMan::IsValidNumArgs(size_t num_args) const
 {
     size_t num_required_args = 0;
@@ -532,8 +547,9 @@ std::string RPCHelpMan::ToString() const
     return ret;
 }
 
-void RPCHelpMan::AppendArgMap(UniValue& arr) const
+UniValue RPCHelpMan::GetArgMap() const
 {
+    UniValue arr{UniValue::VARR};
     for (int i{0}; i < int(m_args.size()); ++i) {
         const auto& arg = m_args.at(i);
         std::vector<std::string> arg_names;
@@ -548,6 +564,7 @@ void RPCHelpMan::AppendArgMap(UniValue& arr) const
             arr.push_back(map);
         }
     }
+    return arr;
 }
 
 std::string RPCArg::GetFirstName() const
diff --git a/src/rpc/util.h b/src/rpc/util.h
index c54ce85f60..94c2d2d626 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -333,26 +333,12 @@ public:
     using RPCMethodImpl = std::function<UniValue(const RPCHelpMan&, const JSONRPCRequest&)>;
     RPCHelpMan(std::string name, std::string description, std::vector<RPCArg> args, RPCResults results, RPCExamples examples, RPCMethodImpl fun);
 
+    UniValue HandleRequest(const JSONRPCRequest& request);
     std::string ToString() const;
-    /** Append the named args that need to be converted from string to another JSON type */
-    void AppendArgMap(UniValue& arr) const;
-    UniValue HandleRequest(const JSONRPCRequest& request)
-    {
-        Check(request);
-        return m_fun(*this, request);
-    }
+    /** Return the named args that need to be converted from string to another JSON type */
+    UniValue GetArgMap() const;
     /** If the supplied number of args is neither too small nor too high */
     bool IsValidNumArgs(size_t num_args) const;
-    /**
-     * Check if the given request is valid according to this command or if
-     * the user is asking for help information, and throw help when appropriate.
-     */
-    inline void Check(const JSONRPCRequest& request) const {
-        if (request.fHelp || !IsValidNumArgs(request.params.size())) {
-            throw std::runtime_error(ToString());
-        }
-    }
-
     std::vector<std::string> GetArgNames() const;
 
     const std::string m_name;