refactoring: add block_index_candidates arg to LoadBlockIndex

Prevents BlockManager from having to reference ChainstateActive()
within one of its methods which improves encapsulation and makes
testing easier.

src/validation.cpp

@@ -3705,7 +3705,10 @@ CBlockIndex * BlockManager::InsertBlockIndex(const uint256& hash)
     return pindexNew;
 }
 
-bool BlockManager::LoadBlockIndex(const Consensus::Params& consensus_params, CBlockTreeDB& blocktree)
+bool BlockManager::LoadBlockIndex(
+    const Consensus::Params& consensus_params,
+    CBlockTreeDB& blocktree,
+    std::set<CBlockIndex*, CBlockIndexWorkComparator>& block_index_candidates)
 {
     if (!blocktree.LoadBlockIndexGuts(consensus_params, [this](const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main) { return this->InsertBlockIndex(hash); }))
         return false;
@@ -3743,8 +3746,9 @@ bool BlockManager::LoadBlockIndex(const Consensus::Params& consensus_params, CBl
             pindex->nStatus |= BLOCK_FAILED_CHILD;
             setDirtyBlockIndex.insert(pindex);
         }
-        if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && (pindex->HaveTxsDownloaded() || pindex->pprev == nullptr))
-            ::ChainstateActive().setBlockIndexCandidates.insert(pindex);
+        if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && (pindex->HaveTxsDownloaded() || pindex->pprev == nullptr)) {
+            block_index_candidates.insert(pindex);
+        }
         if (pindex->nStatus & BLOCK_FAILED_MASK && (!pindexBestInvalid || pindex->nChainWork > pindexBestInvalid->nChainWork))
             pindexBestInvalid = pindex;
         if (pindex->pprev)
@@ -3769,7 +3773,8 @@ void BlockManager::Unload() {
 
 bool static LoadBlockIndexDB(const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
 {
-    if (!g_blockman.LoadBlockIndex(chainparams.GetConsensus(), *pblocktree))
+    if (!g_blockman.LoadBlockIndex(
+            chainparams.GetConsensus(), *pblocktree, ::ChainstateActive().setBlockIndexCandidates))
         return false;
 
     // Load block file info

src/validation.h

@@ -475,9 +475,19 @@ public:
      */
     std::multimap<CBlockIndex*, CBlockIndex*> m_blocks_unlinked;
 
+    /**
+     * Load the blocktree off disk and into memory. Populate certain metadata
+     * per index entry (nStatus, nChainWork, nTimeMax, etc.) as well as peripheral
+     * collections like setDirtyBlockIndex.
+     *
+     * @param[out] block_index_candidates  Fill this set with any valid blocks for
+     *                                     which we've downloaded all transactions.
+     */
     bool LoadBlockIndex(
         const Consensus::Params& consensus_params,
-        CBlockTreeDB& blocktree) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+        CBlockTreeDB& blocktree,
+        std::set<CBlockIndex*, CBlockIndexWorkComparator>& block_index_candidates)
+        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     /** Clear all data members. */
     void Unload() EXCLUSIVE_LOCKS_REQUIRED(cs_main);