rpc: getdeploymentinfo: change stats to always refer to current period

On a period boundary, getdeploymentinfo (and previously getblockchaininfo)
would report the status and statistics for the next block rather than
the current block. Change this to always report the status/statistics
of the current block, but add status-next to report the status for the
next block.

5 files changed, 98 insertions, 59 deletions

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 42993c47f5..dc5c91fe8a 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1412,45 +1412,60 @@ static void SoftForkDescPushBack(const CBlockIndex* active_chain_tip, UniValue&
     // For BIP9 deployments.
 
     if (!DeploymentEnabled(consensusParams, id)) return;
+    if (active_chain_tip == nullptr) return;
+
+    auto get_state_name = [](const ThresholdState state) -> std::string {
+        switch (state) {
+        case ThresholdState::DEFINED: return "defined";
+        case ThresholdState::STARTED: return "started";
+        case ThresholdState::LOCKED_IN: return "locked_in";
+        case ThresholdState::ACTIVE: return "active";
+        case ThresholdState::FAILED: return "failed";
+        }
+        return "invalid";
+    };
 
     UniValue bip9(UniValue::VOBJ);
-    const ThresholdState thresholdState = g_versionbitscache.State(active_chain_tip, consensusParams, id);
-    switch (thresholdState) {
-    case ThresholdState::DEFINED: bip9.pushKV("status", "defined"); break;
-    case ThresholdState::STARTED: bip9.pushKV("status", "started"); break;
-    case ThresholdState::LOCKED_IN: bip9.pushKV("status", "locked_in"); break;
-    case ThresholdState::ACTIVE: bip9.pushKV("status", "active"); break;
-    case ThresholdState::FAILED: bip9.pushKV("status", "failed"); break;
-    }
-    const bool has_signal = (ThresholdState::STARTED == thresholdState || ThresholdState::LOCKED_IN == thresholdState);
+
+    const ThresholdState next_state = g_versionbitscache.State(active_chain_tip, consensusParams, id);
+    const ThresholdState current_state = g_versionbitscache.State(active_chain_tip->pprev, consensusParams, id);
+
+    const bool has_signal = (ThresholdState::STARTED == current_state || ThresholdState::LOCKED_IN == current_state);
+
+    // BIP9 parameters
     if (has_signal) {
         bip9.pushKV("bit", consensusParams.vDeployments[id].bit);
     }
     bip9.pushKV("start_time", consensusParams.vDeployments[id].nStartTime);
     bip9.pushKV("timeout", consensusParams.vDeployments[id].nTimeout);
-    int64_t since_height = g_versionbitscache.StateSinceHeight(active_chain_tip, consensusParams, id);
-    bip9.pushKV("since", since_height);
+    bip9.pushKV("min_activation_height", consensusParams.vDeployments[id].min_activation_height);
+
+    // BIP9 status
+    bip9.pushKV("status", get_state_name(current_state));
+    bip9.pushKV("since", g_versionbitscache.StateSinceHeight(active_chain_tip->pprev, consensusParams, id));
+    bip9.pushKV("status-next", get_state_name(next_state));
+
+    // BIP9 signalling status, if applicable
     if (has_signal) {
         UniValue statsUV(UniValue::VOBJ);
         BIP9Stats statsStruct = g_versionbitscache.Statistics(active_chain_tip, consensusParams, id);
         statsUV.pushKV("period", statsStruct.period);
         statsUV.pushKV("elapsed", statsStruct.elapsed);
         statsUV.pushKV("count", statsStruct.count);
-        if (ThresholdState::LOCKED_IN != thresholdState) {
+        if (ThresholdState::LOCKED_IN != current_state) {
             statsUV.pushKV("threshold", statsStruct.threshold);
             statsUV.pushKV("possible", statsStruct.possible);
         }
         bip9.pushKV("statistics", statsUV);
     }
-    bip9.pushKV("min_activation_height", consensusParams.vDeployments[id].min_activation_height);
 
     UniValue rv(UniValue::VOBJ);
     rv.pushKV("type", "bip9");
-    rv.pushKV("bip9", bip9);
-    if (ThresholdState::ACTIVE == thresholdState) {
-        rv.pushKV("height", since_height);
+    if (ThresholdState::ACTIVE == next_state) {
+        rv.pushKV("height", g_versionbitscache.StateSinceHeight(active_chain_tip, consensusParams, id));
     }
-    rv.pushKV("active", ThresholdState::ACTIVE == thresholdState);
+    rv.pushKV("active", ThresholdState::ACTIVE == next_state);
+    rv.pushKV("bip9", bip9);
 
     softforks.pushKV(DeploymentName(id), rv);
 }
@@ -1551,14 +1566,17 @@ RPCHelpMan getblockchaininfo()
 namespace {
 const std::vector<RPCResult> RPCHelpForDeployment{
     {RPCResult::Type::STR, "type", "one of \"buried\", \"bip9\""},
+    {RPCResult::Type::NUM, "height", /*optional=*/true, "height of the first block which the rules are or will be enforced (only for \"buried\" type, or \"bip9\" type with \"active\" status)"},
+    {RPCResult::Type::BOOL, "active", "true if the rules are enforced for the mempool and the next block"},
     {RPCResult::Type::OBJ, "bip9", /*optional=*/true, "status of bip9 softforks (only for \"bip9\" type)",
     {
-        {RPCResult::Type::STR, "status", "one of \"defined\", \"started\", \"locked_in\", \"active\", \"failed\""},
         {RPCResult::Type::NUM, "bit", /*optional=*/true, "the bit (0-28) in the block version field used to signal this softfork (only for \"started\" and \"locked_in\" status)"},
         {RPCResult::Type::NUM_TIME, "start_time", "the minimum median time past of a block at which the bit gains its meaning"},
         {RPCResult::Type::NUM_TIME, "timeout", "the median time past of a block at which the deployment is considered failed if not yet locked in"},
-        {RPCResult::Type::NUM, "since", "height of the first block to which the status applies"},
         {RPCResult::Type::NUM, "min_activation_height", "minimum height of blocks for which the rules may be enforced"},
+        {RPCResult::Type::STR, "status", "bip9 status of specified block (one of \"defined\", \"started\", \"locked_in\", \"active\", \"failed\")"},
+        {RPCResult::Type::NUM, "since", "height of the first block to which the status applies"},
+        {RPCResult::Type::STR, "status-next", "bip9 status of next block"},
         {RPCResult::Type::OBJ, "statistics", /*optional=*/true, "numeric statistics about signalling for a softfork (only for \"started\" and \"locked_in\" status)",
         {
             {RPCResult::Type::NUM, "period", "the length in blocks of the signalling period"},
@@ -1568,8 +1586,6 @@ const std::vector<RPCResult> RPCHelpForDeployment{
             {RPCResult::Type::BOOL, "possible", /*optional=*/true, "returns false if there are not enough blocks left in this period to pass activation threshold (only for \"started\" status)"},
         }},
     }},
-    {RPCResult::Type::NUM, "height", /*optional=*/true, "height of the first block which the rules are or will be enforced (only for \"buried\" type, or \"bip9\" type with \"active\" status)"},
-    {RPCResult::Type::BOOL, "active", "true if the rules are enforced for the mempool and the next block"},
 };
 
 UniValue DeploymentInfo(const CBlockIndex* tip, const Consensus::Params& consensusParams)
diff --git a/src/test/fuzz/versionbits.cpp b/src/test/fuzz/versionbits.cpp
index cf95c0b9bf..890267db18 100644
--- a/src/test/fuzz/versionbits.cpp
+++ b/src/test/fuzz/versionbits.cpp
@@ -51,7 +51,7 @@ public:
 
     ThresholdState GetStateFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateFor(pindexPrev, dummy_params, m_cache); }
     int GetStateSinceHeightFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateSinceHeightFor(pindexPrev, dummy_params, m_cache); }
-    BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateStatisticsFor(pindexPrev, dummy_params); }
+    BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex) const { return AbstractThresholdConditionChecker::GetStateStatisticsFor(pindex, dummy_params); }
 
     bool Condition(int32_t version) const
     {
@@ -220,7 +220,13 @@ FUZZ_TARGET_INIT(versionbits, initialize)
     CBlockIndex* prev = blocks.tip();
     const int exp_since = checker.GetStateSinceHeightFor(prev);
     const ThresholdState exp_state = checker.GetStateFor(prev);
-    BIP9Stats last_stats = checker.GetStateStatisticsFor(prev);
+
+    // get statistics from end of previous period, then reset
+    BIP9Stats last_stats;
+    last_stats.period = period;
+    last_stats.threshold = threshold;
+    last_stats.count = last_stats.elapsed = 0;
+    last_stats.possible = (period >= threshold);
 
     int prev_next_height = (prev == nullptr ? 0 : prev->nHeight + 1);
     assert(exp_since <= prev_next_height);
@@ -241,9 +247,6 @@ FUZZ_TARGET_INIT(versionbits, initialize)
         assert(state == exp_state);
         assert(since == exp_since);
 
-        // GetStateStatistics may crash when state is not STARTED
-        if (state != ThresholdState::STARTED) continue;
-
         // check that after mining this block stats change as expected
         const BIP9Stats stats = checker.GetStateStatisticsFor(current_block);
         assert(stats.period == period);
@@ -265,14 +268,12 @@ FUZZ_TARGET_INIT(versionbits, initialize)
     CBlockIndex* current_block = blocks.mine_block(signal);
     assert(checker.Condition(current_block) == signal);
 
-    // GetStateStatistics is safe on a period boundary
-    // and has progressed to a new period
     const BIP9Stats stats = checker.GetStateStatisticsFor(current_block);
     assert(stats.period == period);
     assert(stats.threshold == threshold);
-    assert(stats.elapsed == 0);
-    assert(stats.count == 0);
-    assert(stats.possible == true);
+    assert(stats.elapsed == period);
+    assert(stats.count == blocks_sig);
+    assert(stats.possible == (stats.count + period >= stats.elapsed + threshold));
 
     // More interesting is whether the state changed.
     const ThresholdState state = checker.GetStateFor(current_block);
diff --git a/src/versionbits.cpp b/src/versionbits.cpp
index 94c3c9559f..f8945b78b3 100644
--- a/src/versionbits.cpp
+++ b/src/versionbits.cpp
@@ -105,22 +105,23 @@ BIP9Stats AbstractThresholdConditionChecker::GetStateStatisticsFor(const CBlockI
     stats.period = Period(params);
     stats.threshold = Threshold(params);
 
-    if (pindex == nullptr)
-        return stats;
+    if (pindex == nullptr) return stats;
 
     // Find beginning of period
-    const CBlockIndex* pindexEndOfPrevPeriod = pindex->GetAncestor(pindex->nHeight - ((pindex->nHeight + 1) % stats.period));
-    stats.elapsed = pindex->nHeight - pindexEndOfPrevPeriod->nHeight;
+    int start_height = pindex->nHeight - (pindex->nHeight % stats.period);
 
     // Count from current block to beginning of period
+    int elapsed = 0;
     int count = 0;
     const CBlockIndex* currentIndex = pindex;
-    while (pindexEndOfPrevPeriod->nHeight != currentIndex->nHeight){
-        if (Condition(currentIndex, params))
-            count++;
+    for(;;) {
+        ++elapsed;
+        if (Condition(currentIndex, params)) ++count;
+        if (currentIndex->nHeight <= start_height) break;
         currentIndex = currentIndex->pprev;
     }
 
+    stats.elapsed = elapsed;
     stats.count = count;
     stats.possible = (stats.period - stats.threshold ) >= (stats.elapsed - count);
 
@@ -196,9 +197,9 @@ ThresholdState VersionBitsCache::State(const CBlockIndex* pindexPrev, const Cons
     return VersionBitsConditionChecker(pos).GetStateFor(pindexPrev, params, m_caches[pos]);
 }
 
-BIP9Stats VersionBitsCache::Statistics(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos)
+BIP9Stats VersionBitsCache::Statistics(const CBlockIndex* pindex, const Consensus::Params& params, Consensus::DeploymentPos pos)
 {
-    return VersionBitsConditionChecker(pos).GetStateStatisticsFor(pindexPrev, params);
+    return VersionBitsConditionChecker(pos).GetStateStatisticsFor(pindex, params);
 }
 
 int VersionBitsCache::StateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos)
diff --git a/src/versionbits.h b/src/versionbits.h
index 0b2f4a0258..34fba47b5f 100644
--- a/src/versionbits.h
+++ b/src/versionbits.h
@@ -64,7 +64,7 @@ protected:
     virtual int Threshold(const Consensus::Params& params) const =0;
 
 public:
-    /** Returns the numerical statistics of an in-progress BIP9 softfork in the current period */
+    /** Returns the numerical statistics of an in-progress BIP9 softfork in the period including pindex */
     BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, const Consensus::Params& params) const;
     /** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present.
      *  Caches state from first block of period. */
@@ -82,8 +82,8 @@ private:
     ThresholdConditionCache m_caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS] GUARDED_BY(m_mutex);
 
 public:
-    /** Get the numerical statistics for a given deployment for the signalling period that includes the block after pindexPrev. */
-    static BIP9Stats Statistics(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos);
+    /** Get the numerical statistics for a given deployment for the signalling period that includes pindex. */
+    static BIP9Stats Statistics(const CBlockIndex* pindex, const Consensus::Params& params, Consensus::DeploymentPos pos);
 
     static uint32_t Mask(const Consensus::Params& params, Consensus::DeploymentPos pos);
 
diff --git a/test/functional/rpc_blockchain.py b/test/functional/rpc_blockchain.py
index 9b9f989b04..2498543bbe 100755
--- a/test/functional/rpc_blockchain.py
+++ b/test/functional/rpc_blockchain.py
@@ -72,7 +72,6 @@ class BlockchainTest(BitcoinTestFramework):
         self.restart_node(0, extra_args=['-stopatheight=207', '-prune=1'])  # Set extra args with pruning after rescan is complete
 
         self._test_getblockchaininfo()
-        self._test_getdeploymentinfo()
         self._test_getchaintxstats()
         self._test_gettxoutsetinfo()
         self._test_getblockheader()
@@ -81,6 +80,7 @@ class BlockchainTest(BitcoinTestFramework):
         self._test_stopatheight()
         self._test_waitforblockheight()
         self._test_getblock()
+        self._test_getdeploymentinfo()
         assert self.nodes[0].verifychain(4, 0)
 
     def mine_chain(self):
@@ -160,11 +160,6 @@ class BlockchainTest(BitcoinTestFramework):
         self.start_node(0, extra_args=[
             '-stopatheight=207',
             '-prune=550',
-            '-testactivationheight=bip34@2',
-            '-testactivationheight=dersig@3',
-            '-testactivationheight=cltv@4',
-            '-testactivationheight=csv@5',
-            '-testactivationheight=segwit@6',
         ])
 
         res = self.nodes[0].getblockchaininfo()
@@ -178,11 +173,10 @@ class BlockchainTest(BitcoinTestFramework):
         assert_equal(res['prune_target_size'], 576716800)
         assert_greater_than(res['size_on_disk'], 0)
 
-    def _test_getdeploymentinfo(self):
-        self.log.info("Test getdeploymentinfo")
+    def check_signalling_deploymentinfo_result(self, gdi_result, height, blockhash, status_next):
+        assert height >= 144 and height <= 287
 
-        res = self.nodes[0].getdeploymentinfo()
-        assert_equal(res, {
+        assert_equal(gdi_result, {
           "deployments": {
             'bip34': {'type': 'buried', 'active': True, 'height': 2},
             'bip66': {'type': 'buried', 'active': True, 'height': 3},
@@ -192,30 +186,32 @@ class BlockchainTest(BitcoinTestFramework):
             'testdummy': {
                 'type': 'bip9',
                 'bip9': {
-                    'status': 'started',
                     'bit': 28,
                     'start_time': 0,
                     'timeout': 0x7fffffffffffffff,  # testdummy does not have a timeout so is set to the max int64 value
+                    'min_activation_height': 0,
+                    'status': 'started',
+                    'status-next': status_next,
                     'since': 144,
                     'statistics': {
                         'period': 144,
                         'threshold': 108,
-                        'elapsed': HEIGHT - 143,
-                        'count': HEIGHT - 143,
+                        'elapsed': height - 143,
+                        'count': height - 143,
                         'possible': True,
                     },
-                    'min_activation_height': 0,
                 },
                 'active': False
             },
             'taproot': {
                 'type': 'bip9',
                 'bip9': {
-                    'status': 'active',
                     'start_time': -1,
                     'timeout': 9223372036854775807,
-                    'since': 0,
                     'min_activation_height': 0,
+                    'status': 'active',
+                    'status-next': 'active',
+                    'since': 0,
                 },
                 'height': 0,
                 'active': True
@@ -223,6 +219,31 @@ class BlockchainTest(BitcoinTestFramework):
           }
         })
 
+    def _test_getdeploymentinfo(self):
+        # Note: continues past -stopatheight height, so must be invoked
+        # after _test_stopatheight
+
+        self.log.info("Test getdeploymentinfo")
+        self.stop_node(0)
+        self.start_node(0, extra_args=[
+            '-testactivationheight=bip34@2',
+            '-testactivationheight=dersig@3',
+            '-testactivationheight=cltv@4',
+            '-testactivationheight=csv@5',
+            '-testactivationheight=segwit@6',
+        ])
+
+        gbci207 = self.nodes[0].getblockchaininfo()
+        self.check_signalling_deploymentinfo_result(self.nodes[0].getdeploymentinfo(), gbci207["blocks"], gbci207["bestblockhash"], "started")
+
+        # block just prior to lock in
+        self.generate(self.wallet, 287 - gbci207["blocks"])
+        gbci287 = self.nodes[0].getblockchaininfo()
+        self.check_signalling_deploymentinfo_result(self.nodes[0].getdeploymentinfo(), gbci287["blocks"], gbci287["bestblockhash"], "locked_in")
+
+        # calling with an explicit hash works
+        self.check_signalling_deploymentinfo_result(self.nodes[0].getdeploymentinfo(gbci207["bestblockhash"]), gbci207["blocks"], gbci207["bestblockhash"], "started")
+
     def _test_getchaintxstats(self):
         self.log.info("Test getchaintxstats")