Merge bitcoin/bitcoin#21767: [Bundle 6/n] Prune g_chainman usage in auxiliary modules

7a799c9c2b8652e780d1fd5e1bf7d05b026c1c1a index: refactor-only: Reuse CChain ref (Carl Dong)
db33cde80fff749c6adff9e91fca5f27f4bb6278 index: Add chainstate member to BaseIndex (Carl Dong)
f4a47a1febfa35ab077f2a841fe31a8cd9618250 bench: Use existing chainman in AssembleBlock (Carl Dong)
91226eb91769aad5a63bc671595e1353a2b2247a bench: Use existing NodeContext in DuplicateInputs (Carl Dong)
e6b4aa6eb53dc555ecab2922af35e7a2572faf4f miner: Pass in chainman to RegenerateCommitments (Carl Dong)
9ecade14252ad1972f668d2d2e4ef44fdfcb944a rest: Add GetChainman function and use it (Carl Dong)
fc1c282845f6b8436d1ea4c68eb3511034c29bea rpc/blockchain: Use existing blockman in gettxoutsetinfo (Carl Dong)

Pull request description:

  Overall PR: #20158 (tree-wide: De-globalize ChainstateManager)

  The first 2 commits are fixups addressing review for the last bundle: #21391

  NEW note:
  1. I have opened #21766 which keeps track of potential improvements where the flaws already existed before the de-globalization work, please post on that issue about these improvements, thanks!

  Note to reviewers:
  1. This bundle may _apparently_ introduce usage of `g_chainman` or `::Chain(state|)Active()` globals, but these are resolved later on in the overall PR. [Commits of overall PR](https://github.com/bitcoin/bitcoin/pull/20158/commits)
  2. There may be seemingly obvious local references to `ChainstateManager` or other validation objects which are not being used in callers of the current function in question, this is done intentionally to **_keep each commit centered around one function/method_** to ease review and to make the overall change systematic. We don't assume anything about our callers. Rest assured that once we are considering that particular caller in later commits, we will use the obvious local references. [Commits of overall PR](https://github.com/bitcoin/bitcoin/pull/20158/commits)
  3. When changing a function/method that has many callers (e.g. `LookupBlockIndex` with 55 callers), it is sometimes easier (and less error-prone) to use a scripted-diff. When doing so, there will be 3 commits in sequence so that every commit compiles like so:
  1. Add `new_function`, make `old_function` a wrapper of `new_function`, divert all calls to `old_function` to `new_function` **in the local module only**
  2. Scripted-diff to divert all calls to `old_function` to `new_function` **in the rest of the codebase**
  3. Remove `old_function`

ACKs for top commit:
  jarolrod:
    ACK  7a799c9
  ariard:
    Code Review ACK 7a799c9
  fjahr:
    re-ACK 7a799c9c2b8652e780d1fd5e1bf7d05b026c1c1a
  MarcoFalke:
    review ACK 7a799c9c2b8652e780d1fd5e1bf7d05b026c1c1a 🌠
  ryanofsky:
    Code review ACK 7a799c9c2b8652e780d1fd5e1bf7d05b026c1c1a. Basically no change since last review except fixed rebase conflicts and a new comment about REST Ensure()
  jamesob:
    conditional ACK 7a799c9c2b8652e780d1fd5e1bf7d05b026c1c1a ([`jamesob/ackr/21767.1.dongcarl.bundle_6_n_prune_g_chai`](https://github.com/jamesob/bitcoin/tree/ackr/21767.1.dongcarl.bundle_6_n_prune_g_chai))

Tree-SHA512: 531c00ddcb318817457db2812d9a9d930bc664e58e6f7f1c746350732b031dd624270bfa6b9f49d8056aeb6321d973f0e38e4ff914acd6768edd8602c017d10e

1 files changed, 33 insertions, 4 deletions

diff --git a/src/rest.cpp b/src/rest.cpp
index d41f374c49..747c7aea19 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -107,6 +107,27 @@ static CTxMemPool* GetMemPool(const std::any& context, HTTPRequest* req)
     return node_context->mempool.get();
 }
 
+/**
+ * Get the node context chainstatemanager.
+ *
+ * @param[in]  req The HTTP request, whose status code will be set if node
+ *                 context chainstatemanager is not found.
+ * @returns        Pointer to the chainstatemanager or nullptr if none found.
+ */
+static ChainstateManager* GetChainman(const std::any& context, HTTPRequest* req)
+{
+    auto node_context = util::AnyPtr<NodeContext>(context);
+    if (!node_context || !node_context->chainman) {
+        RESTERR(req, HTTP_INTERNAL_SERVER_ERROR,
+                strprintf("%s:%d (%s)\n"
+                          "Internal bug detected: Chainman disabled or instance not found!\n"
+                          "You may report this issue here: %s\n",
+                          __FILE__, __LINE__, __func__, PACKAGE_BUGREPORT));
+        return nullptr;
+    }
+    return node_context->chainman;
+}
+
 static RetFormat ParseDataFormat(std::string& param, const std::string& strReq)
 {
     const std::string::size_type pos = strReq.rfind('.');
@@ -181,7 +202,9 @@ static bool rest_headers(const std::any& context,
     std::vector<const CBlockIndex *> headers;
     headers.reserve(count);
     {
-        ChainstateManager& chainman = EnsureAnyChainman(context);
+        ChainstateManager* maybe_chainman = GetChainman(context, req);
+        if (!maybe_chainman) return false;
+        ChainstateManager& chainman = *maybe_chainman;
         LOCK(cs_main);
         CChain& active_chain = chainman.ActiveChain();
         tip = active_chain.Tip();
@@ -252,7 +275,9 @@ static bool rest_block(const std::any& context,
     CBlockIndex* pblockindex = nullptr;
     CBlockIndex* tip = nullptr;
     {
-        ChainstateManager& chainman = EnsureAnyChainman(context);
+        ChainstateManager* maybe_chainman = GetChainman(context, req);
+        if (!maybe_chainman) return false;
+        ChainstateManager& chainman = *maybe_chainman;
         LOCK(cs_main);
         tip = chainman.ActiveChain().Tip();
         pblockindex = chainman.m_blockman.LookupBlockIndex(hash);
@@ -541,7 +566,9 @@ static bool rest_getutxos(const std::any& context, HTTPRequest* req, const std::
     std::string bitmapStringRepresentation;
     std::vector<bool> hits;
     bitmap.resize((vOutPoints.size() + 7) / 8);
-    ChainstateManager& chainman = EnsureAnyChainman(context);
+    ChainstateManager* maybe_chainman = GetChainman(context, req);
+    if (!maybe_chainman) return false;
+    ChainstateManager& chainman = *maybe_chainman;
     {
         auto process_utxos = [&vOutPoints, &outs, &hits](const CCoinsView& view, const CTxMemPool& mempool) {
             for (const COutPoint& vOutPoint : vOutPoints) {
@@ -644,7 +671,9 @@ static bool rest_blockhash_by_height(const std::any& context, HTTPRequest* req,
 
     CBlockIndex* pblockindex = nullptr;
     {
-        ChainstateManager& chainman = EnsureAnyChainman(context);
+        ChainstateManager* maybe_chainman = GetChainman(context, req);
+        if (!maybe_chainman) return false;
+        ChainstateManager& chainman = *maybe_chainman;
         LOCK(cs_main);
         const CChain& active_chain = chainman.ActiveChain();
         if (blockheight > active_chain.Height()) {