Merge #18740: Remove g_rpc_node global

b3f7f375efb9a9ca9a7a4f2caf41fe3df2262520 refactor: Remove g_rpc_node global (Russell Yanofsky)
ccb5059ee89f6e8dc31ba5b82830b384890bb65e scripted-diff: Remove g_rpc_node references (Russell Yanofsky)
6fca33b2edc09ed62dab2323c780b31585de1750 refactor: Pass NodeContext to RPC and REST methods through util::Ref (Russell Yanofsky)
691c817b340d10e806dc3b1834d2a8fcc5e681fd Add util::Ref class as temporary alternative for c++17 std::any (Russell Yanofsky)

Pull request description:

  This PR removes the `g_rpc_node` global, to get same benefits we see removing other globals and make RPC code more testable, modular, and reusable.

  This uses a hybrid of the approaches suggested in #17548. Instead of using `std::any`, which isn't available in c++11, or `void*`, which isn't type safe, it uses a small new `util::Ref` helper class, which acts like a simplified `std::any` that only holds references, not values.

  Motivation for writing this was to provide an simpler alternative to #18647 by Harris Brakmić (brakmic) which avoids some shortcomings of that PR (https://github.com/bitcoin/bitcoin/pull/18647#issuecomment-617878826)

ACKs for top commit:
  MarcoFalke:
    re-ACK b3f7f375ef, only change is adding back const and more tests 🚾
  ajtowns:
    ACK b3f7f375efb9a9ca9a7a4f2caf41fe3df2262520

Tree-SHA512: 56292268a001bdbe34d641db1180c215351503966ff451e55cc96c9137f1d262225d7d7733de9c9da7ce7d7a4b34213a98c2476266b58c89dbbb0f3cb5aa5d70

3 files changed, 45 insertions, 6 deletions

diff --git a/src/test/ref_tests.cpp b/src/test/ref_tests.cpp
new file mode 100644
index 0000000000..0ec0799fbc
--- /dev/null
+++ b/src/test/ref_tests.cpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <util/ref.h>
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_AUTO_TEST_SUITE(ref_tests)
+
+BOOST_AUTO_TEST_CASE(ref_test)
+{
+    util::Ref ref;
+    BOOST_CHECK(!ref.Has<int>());
+    BOOST_CHECK_THROW(ref.Get<int>(), NonFatalCheckError);
+    int value = 5;
+    ref.Set(value);
+    BOOST_CHECK(ref.Has<int>());
+    BOOST_CHECK_EQUAL(ref.Get<int>(), 5);
+    ++ref.Get<int>();
+    BOOST_CHECK_EQUAL(ref.Get<int>(), 6);
+    BOOST_CHECK_EQUAL(value, 6);
+    ++value;
+    BOOST_CHECK_EQUAL(value, 7);
+    BOOST_CHECK_EQUAL(ref.Get<int>(), 7);
+    BOOST_CHECK(!ref.Has<bool>());
+    BOOST_CHECK_THROW(ref.Get<bool>(), NonFatalCheckError);
+    ref.Clear();
+    BOOST_CHECK(!ref.Has<int>());
+    BOOST_CHECK_THROW(ref.Get<int>(), NonFatalCheckError);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/test/rpc_tests.cpp b/src/test/rpc_tests.cpp
index d9c66f1c19..b54cbb3f00 100644
--- a/src/test/rpc_tests.cpp
+++ b/src/test/rpc_tests.cpp
@@ -10,6 +10,7 @@
 #include <interfaces/chain.h>
 #include <node/context.h>
 #include <test/util/setup_common.h>
+#include <util/ref.h>
 #include <util/time.h>
 
 #include <boost/algorithm/string.hpp>
@@ -19,13 +20,20 @@
 
 #include <rpc/blockchain.h>
 
-UniValue CallRPC(std::string args)
+class RPCTestingSetup : public TestingSetup
+{
+public:
+    UniValue CallRPC(std::string args);
+};
+
+UniValue RPCTestingSetup::CallRPC(std::string args)
 {
     std::vector<std::string> vArgs;
     boost::split(vArgs, args, boost::is_any_of(" \t"));
     std::string strMethod = vArgs[0];
     vArgs.erase(vArgs.begin());
-    JSONRPCRequest request;
+    util::Ref context{m_node};
+    JSONRPCRequest request(context);
     request.strMethod = strMethod;
     request.params = RPCConvertValues(strMethod, vArgs);
     request.fHelp = false;
@@ -40,7 +48,7 @@ UniValue CallRPC(std::string args)
 }
 
 
-BOOST_FIXTURE_TEST_SUITE(rpc_tests, TestingSetup)
+BOOST_FIXTURE_TEST_SUITE(rpc_tests, RPCTestingSetup)
 
 BOOST_AUTO_TEST_CASE(rpc_rawparams)
 {
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index bf0afc4171..86dac55b2b 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -123,7 +123,6 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
     const CChainParams& chainparams = Params();
     // Ideally we'd move all the RPC tests to the functional testing framework
     // instead of unit tests, but for now we need these here.
-    g_rpc_node = &m_node;
     RegisterAllCoreRPCCommands(tableRPC);
 
     m_node.scheduler = MakeUnique<CScheduler>();
@@ -131,7 +130,7 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
     // We have to run a scheduler thread to prevent ActivateBestChain
     // from blocking due to queue overrun.
     threadGroup.create_thread([&]{ m_node.scheduler->serviceQueue(); });
-    GetMainSignals().RegisterBackgroundSignalScheduler(*g_rpc_node->scheduler);
+    GetMainSignals().RegisterBackgroundSignalScheduler(*m_node.scheduler);
 
     pblocktree.reset(new CBlockTreeDB(1 << 20, true));
 
@@ -176,7 +175,6 @@ TestingSetup::~TestingSetup()
     threadGroup.join_all();
     GetMainSignals().FlushBackgroundCallbacks();
     GetMainSignals().UnregisterBackgroundSignalScheduler();
-    g_rpc_node = nullptr;
     m_node.connman.reset();
     m_node.banman.reset();
     m_node.args = nullptr;