validation: report if pruning prevents completion of verification

Now the verifychain RPC returns false if the checks didn't
finish because the blocks requested to be queried have been pruned.

src/node/chainstate.cpp

@@ -194,6 +194,7 @@ ChainstateLoadResult VerifyLoadedChainstate(ChainstateManager& chainman, const C
             switch (result) {
             case VerifyDBResult::SUCCESS:
             case VerifyDBResult::INTERRUPTED:
+            case VerifyDBResult::SKIPPED_MISSING_BLOCKS:
                 break;
             case VerifyDBResult::CORRUPTED_BLOCK_DB:
                 return {ChainstateLoadStatus::FAILURE, _("Corrupted block database detected")};

src/validation.cpp

@@ -4081,6 +4081,7 @@ VerifyDBResult CVerifyDB::VerifyDB(
     int nGoodTransactions = 0;
     BlockValidationState state;
     int reportDone = 0;
+    bool skipped_no_block_data{false};
     bool skipped_l3_checks{false};
     LogPrintf("Verification progress: 0%%\n");
 
@@ -4100,7 +4101,8 @@ VerifyDBResult CVerifyDB::VerifyDB(
         if ((chainstate.m_blockman.IsPruneMode() || is_snapshot_cs) && !(pindex->nStatus & BLOCK_HAVE_DATA)) {
             // If pruning or running under an assumeutxo snapshot, only go
             // back as far as we have data.
-            LogPrintf("VerifyDB(): block verification stopping at height %d (pruning, no data)\n", pindex->nHeight);
+            LogPrintf("VerifyDB(): block verification stopping at height %d (no data). This could be due to pruning or use of an assumeutxo snapshot.\n", pindex->nHeight);
+            skipped_no_block_data = true;
             break;
         }
         CBlock block;
@@ -4188,6 +4190,9 @@ VerifyDBResult CVerifyDB::VerifyDB(
     if (skipped_l3_checks) {
         return VerifyDBResult::SKIPPED_L3_CHECKS;
     }
+    if (skipped_no_block_data) {
+        return VerifyDBResult::SKIPPED_MISSING_BLOCKS;
+    }
     return VerifyDBResult::SUCCESS;
 }
 

src/validation.h

@@ -354,6 +354,7 @@ enum class VerifyDBResult {
     CORRUPTED_BLOCK_DB,
     INTERRUPTED,
     SKIPPED_L3_CHECKS,
+    SKIPPED_MISSING_BLOCKS,
 };
 
 /** RAII wrapper for VerifyDB: Verify consistency of the block and coin databases */

test/functional/feature_pruning.py

@@ -223,8 +223,8 @@ class PruneTest(BitcoinTestFramework):
     def reorg_back(self):
         # Verify that a block on the old main chain fork has been pruned away
         assert_raises_rpc_error(-1, "Block not available (pruned data)", self.nodes[2].getblock, self.forkhash)
-        with self.nodes[2].assert_debug_log(expected_msgs=['block verification stopping at height', '(pruning, no data)']):
-            self.nodes[2].verifychain(checklevel=4, nblocks=0)
+        with self.nodes[2].assert_debug_log(expected_msgs=['block verification stopping at height', '(no data)']):
+            assert not self.nodes[2].verifychain(checklevel=4, nblocks=0)
         self.log.info(f"Will need to redownload block {self.forkheight}")
 
         # Verify that we have enough history to reorg back to the fork point