[rpc] Deprecate estimatefee RPC

Deprecate estimatefee in v0.16, for final removal in v0.17.

This commit introduces a phased removal of RPC methods. RPC method is
disabled by default in version x, but can be enabled by using the
`-deprecatedrpc=<method>` argument. RPC method is removed entirely in
version (x+1).

4 files changed, 16 insertions, 0 deletions

diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index f0ffa07e12..5ac32dc974 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -789,6 +789,12 @@ UniValue estimatefee(const JSONRPCRequest& request)
             + HelpExampleCli("estimatefee", "6")
             );
 
+    if (!IsDeprecatedRPCEnabled("estimatefee")) {
+        throw JSONRPCError(RPC_METHOD_DEPRECATED, "estimatefee is deprecated and will be fully removed in v0.17. "
+            "To use estimatefee in v0.16, restart bitcoind with -deprecatedrpc=estimatefee.\n"
+            "Projects should transition to using estimatesmartfee before upgrading to v0.17");
+    }
+
     RPCTypeCheck(request.params, {UniValue::VNUM});
 
     int nBlocks = request.params[0].get_int();
diff --git a/src/rpc/protocol.h b/src/rpc/protocol.h
index 5c9c64f67d..056f93e7db 100644
--- a/src/rpc/protocol.h
+++ b/src/rpc/protocol.h
@@ -57,6 +57,7 @@ enum RPCErrorCode
     RPC_VERIFY_REJECTED             = -26, //!< Transaction or block was rejected by network rules
     RPC_VERIFY_ALREADY_IN_CHAIN     = -27, //!< Transaction already in chain
     RPC_IN_WARMUP                   = -28, //!< Client still warming up
+    RPC_METHOD_DEPRECATED           = -32, //!< RPC method is deprecated
 
     //! Aliases for backward compatibility
     RPC_TRANSACTION_ERROR           = RPC_VERIFY_ERROR,
diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
index 428ab3b9b0..a73b697e01 100644
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -382,6 +382,13 @@ void JSONRPCRequest::parse(const UniValue& valRequest)
         throw JSONRPCError(RPC_INVALID_REQUEST, "Params must be an array or object");
 }
 
+bool IsDeprecatedRPCEnabled(const std::string& method)
+{
+    const std::vector<std::string> enabled_methods = gArgs.GetArgs("-deprecatedrpc");
+
+    return find(enabled_methods.begin(), enabled_methods.end(), method) != enabled_methods.end();
+}
+
 static UniValue JSONRPCExecOne(const UniValue& req)
 {
     UniValue rpc_result(UniValue::VOBJ);
diff --git a/src/rpc/server.h b/src/rpc/server.h
index 777acbcb94..31d6304271 100644
--- a/src/rpc/server.h
+++ b/src/rpc/server.h
@@ -171,6 +171,8 @@ public:
     bool appendCommand(const std::string& name, const CRPCCommand* pcmd);
 };
 
+bool IsDeprecatedRPCEnabled(const std::string& method);
+
 extern CRPCTable tableRPC;
 
 /**