SERVER-44748 do not ignore write conflict exceptions for write transactions

In debug mode, we check that the catalog is consistent when fetching the total number of indexes.  This check might encounter a WT_ROLLBACK, so suppress such WCE's.  We can only safely do this for read transactions, since such transactions cannot be subsequently committed, due to the rollback error.

src/mongo/db/catalog/index_catalog_impl.cpp

@@ -47,6 +47,7 @@
 #include "mongo/db/catalog/uncommitted_collections.h"
 #include "mongo/db/client.h"
 #include "mongo/db/clientcursor.h"
+#include "mongo/db/concurrency/write_conflict_exception.h"
 #include "mongo/db/curop.h"
 #include "mongo/db/field_ref.h"
 #include "mongo/db/fts/fts_spec.h"
@@ -1025,8 +1026,26 @@ bool IndexCatalogImpl::haveAnyIndexesInProgress() const {
 
 int IndexCatalogImpl::numIndexesTotal(OperationContext* opCtx) const {
     int count = _readyIndexes.size() + _buildingIndexes.size();
-    dassert(DurableCatalog::get(opCtx)->getTotalIndexCount(opCtx, _collection->getCatalogId()) ==
-            count);
+
+    if (kDebugBuild) {
+        try {
+            // Check if the in-memory index count matches the durable catalogs index count on disk.
+            // This can throw a WriteConflictException when retries on write conflicts are disabled
+            // during testing. The DurableCatalog fetches the metadata off of the disk using a
+            // findRecord() call.
+            dassert(DurableCatalog::get(opCtx)->getTotalIndexCount(
+                        opCtx, _collection->getCatalogId()) == count);
+        } catch (const WriteConflictException& ex) {
+            if (opCtx->lockState()->isWriteLocked()) {
+                // Must abort this write transaction now.
+                throw;
+            }
+            // Ignore the write conflict for read transactions; we will eventually roll back this
+            // transaction anyway.
+            log() << " Skipping dassert check due to: " << ex;
+        }
+    }
+
     return count;
 }