ChainSel: reprocess LoE-delayed blocks even when LoE is disabled

When Genesis is disable statically, we never even schedule any LoE reprocessing,
so this doesn't change anything in this situation.

When Genesis is disabled and we are caught-up, then there are concrete scenarios
where we want to reprocess LoE blocks, see the preceding two commits.

Author: amesgen

ouroboros-consensus/changelog.d/20250512_164809_alexander.esgen_genesis_caughtup_final_chainsel.md

@@ -0,0 +1,3 @@
+### Patch
+
+- Changed ChainSel to reprocess LoE-delayed blocks even when LoE is disabled.

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Storage/ChainDB/Impl/ChainSel.hs

@@ -332,29 +332,29 @@ chainSelSync ::
 -- We run a background thread that polls the candidate fragments and sends
 -- 'ChainSelReprocessLoEBlocks' whenever we receive a new header or lose a
 -- peer.
--- If 'cdbLoE' is 'LoEDisabled', this task is skipped.
+--
+-- Note that we do this even when we are caught-up, as we might want to select
+-- blocks that were originally postponed by the LoE, but can be adopted once we
+-- conclude that we are caught-up (and hence are longer bound by the LoE).
 chainSelSync cdb@CDB{..} (ChainSelReprocessLoEBlocks varProcessed) = do
-    lift cdbLoE >>= \case
-      LoEDisabled  -> pure ()
-      LoEEnabled _ -> do
-        (succsOf, chain) <- lift $ atomically $ do
-          invalid <- forgetFingerprint <$> readTVar cdbInvalid
-          (,)
-            <$> (ignoreInvalidSuc cdbVolatileDB invalid <$>
-              VolatileDB.filterByPredecessor cdbVolatileDB)
-            <*> Query.getCurrentChain cdb
-        let
-            succsOf' = Set.toList . succsOf . pointHash . castPoint
-            loeHashes = succsOf' (AF.anchorPoint chain)
-            firstHeader = either (const Nothing) Just $ AF.last chain
-            -- We avoid the VolatileDB for the headers we already have in the chain
-            getHeaderFromHash hash =
-              case firstHeader of
-                Just header | headerHash header == hash -> pure header
-                _ -> VolatileDB.getKnownBlockComponent cdbVolatileDB GetHeader hash
-        loeHeaders <- lift (mapM getHeaderFromHash loeHashes)
-        for_ loeHeaders $ \hdr ->
-          chainSelectionForBlock cdb BlockCache.empty hdr noPunishment
+    (succsOf, chain) <- lift $ atomically $ do
+      invalid <- forgetFingerprint <$> readTVar cdbInvalid
+      (,)
+        <$> (ignoreInvalidSuc cdbVolatileDB invalid <$>
+          VolatileDB.filterByPredecessor cdbVolatileDB)
+        <*> Query.getCurrentChain cdb
+    let
+        succsOf' = Set.toList . succsOf . pointHash . castPoint
+        loeHashes = succsOf' (AF.anchorPoint chain)
+        firstHeader = either (const Nothing) Just $ AF.last chain
+        -- We avoid the VolatileDB for the headers we already have in the chain
+        getHeaderFromHash hash =
+          case firstHeader of
+            Just header | headerHash header == hash -> pure header
+            _ -> VolatileDB.getKnownBlockComponent cdbVolatileDB GetHeader hash
+    loeHeaders <- lift (mapM getHeaderFromHash loeHashes)
+    for_ loeHeaders $ \hdr ->
+      chainSelectionForBlock cdb BlockCache.empty hdr noPunishment
     lift $ atomically $ putTMVar varProcessed ()
 
 chainSelSync cdb@CDB {..} (ChainSelAddBlock BlockToAdd { blockToAdd = b, .. }) = do