rpc: Tidy up local references (see commit message)

Organize local variables/references such that:

1. There is always a `ChainstateManager` reference before any `LOCK(cs_main)`.
2. NodeContext references are used with Ensure*() functions introduced in
   previous commit where appropriate to avoid duplicate assertions.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/rest.cpp b/src/rest.cpp
index dd2d649ff4..eea0d67882 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -180,8 +180,8 @@ static bool rest_headers(const std::any& context,
     std::vector<const CBlockIndex *> headers;
     headers.reserve(count);
     {
-        LOCK(cs_main);
         ChainstateManager& chainman = EnsureAnyChainman(context);
+        LOCK(cs_main);
         tip = chainman.ActiveChain().Tip();
         const CBlockIndex* pindex = chainman.m_blockman.LookupBlockIndex(hash);
         while (pindex != nullptr && chainman.ActiveChain().Contains(pindex)) {
@@ -250,8 +250,8 @@ static bool rest_block(const std::any& context,
     CBlockIndex* pblockindex = nullptr;
     CBlockIndex* tip = nullptr;
     {
-        LOCK(cs_main);
         ChainstateManager& chainman = EnsureAnyChainman(context);
+        LOCK(cs_main);
         tip = chainman.ActiveChain().Tip();
         pblockindex = chainman.m_blockman.LookupBlockIndex(hash);
         if (!pblockindex) {
@@ -641,8 +641,9 @@ static bool rest_blockhash_by_height(const std::any& context, HTTPRequest* req,
 
     CBlockIndex* pblockindex = nullptr;
     {
+        ChainstateManager& chainman = EnsureAnyChainman(context);
         LOCK(cs_main);
-        const CChain& active_chain = EnsureAnyChainman(context).ActiveChain();
+        const CChain& active_chain = chainman.ActiveChain();
         if (blockheight > active_chain.Height()) {
             return RESTERR(req, HTTP_NOT_FOUND, "Block height out of range");
         }