CXXCBC-683: Txn replace - Use CAS from given TransactionsGetResult when document is a staged insert (#763)

Author: DemetrisChr

core/transactions/attempt_context_impl.cxx

@@ -670,7 +670,7 @@ attempt_context_impl::replace(const transaction_get_result& document,
                         self, "found existing INSERT of {} while replacing", document);
                       self->create_staged_insert(document.id(),
                                                  std::move(content),
-                                                 existing_sm->cas().value(),
+                                                 document.cas().value(),
                                                  exp_delay(std::chrono::milliseconds(5),
                                                            std::chrono::milliseconds(300),
                                                            self->overall()->config().timeout),

test/test_transaction_public_blocking_api.cxx

@@ -765,3 +765,70 @@ TEST_CASE("transactions public blocking API: can remove doc in bucket not yet op
     CHECK(get_err.ec() == couchbase::errc::key_value::document_not_found);
   });
 }
+
+TEST_CASE("transactions public blocking API: insert then replace with illegal document "
+          "modification in-between",
+          "[transactions]")
+{
+  test::utils::integration_test_guard integration;
+
+  if (!integration.cluster_version().supports_replace_body_with_xattr()) {
+    // If replace_body_with_xattr is not supported, we have the staged insert's content in memory,
+    // so the transactional get will not fetch the document from the server, which would give the
+    // up-to-date CAS.
+    SKIP("the server does not support replace_body_with_xattr");
+  }
+
+  auto doc_id = test::utils::uniq_id("txn");
+  auto txn_content_initial = tao::json::value{ { "num", 12 } };
+  auto txn_content_updated = tao::json::value{ { "num", 20 } };
+  auto illegal_content = tao::json::value{ { "illegal", "content" } };
+
+  auto cluster = integration.public_cluster();
+  auto collection = cluster.bucket(integration.ctx.bucket).default_collection();
+
+  auto [tx_err, result] = cluster.transactions()->run(
+    [&doc_id, &collection, &txn_content_initial, &txn_content_updated, &illegal_content](
+      std::shared_ptr<couchbase::transactions::attempt_context> ctx) -> couchbase::error {
+      // Stage an insert
+      {
+        auto [err, res] = ctx->insert(collection, doc_id, txn_content_initial);
+        if (err) {
+          return err;
+        }
+        REQUIRE(res.content_as<tao::json::value>() == txn_content_initial);
+      }
+
+      // Do an illegal non-transactional insert that will override any staged content and txn
+      // metadata
+      {
+        auto [err, res] = collection.insert(doc_id, illegal_content).get();
+        REQUIRE_SUCCESS(err.ec());
+      }
+
+      {
+        // Now that we implement ExtReplaceBodyWithXattr, this will fetch the document from the
+        // server (post-illegal mutation) as the staged content of the staged mutation is not stored
+        // in memory.
+        auto [get_err, get_res] = ctx->get(collection, doc_id);
+        if (get_err) {
+          return get_err;
+        }
+        REQUIRE(get_res.content_as<tao::json::value>() == illegal_content);
+
+        // This replace will use the CAS from the transaction_get_result, which should be the one
+        // after the illegal insert. This means the operation will succeed, and will result in a
+        // staged insert with the CAS from the transaction_get_result.
+        // When committing, the replace_body_with_xattr op, and the transaction, will succeed.
+        auto [replace_err, replace_res] = ctx->replace(get_res, txn_content_updated);
+        if (replace_err) {
+          return replace_err;
+        }
+        REQUIRE(replace_res.content_as<tao::json::value>() == txn_content_updated);
+      }
+
+      return {};
+    });
+
+  REQUIRE_SUCCESS(tx_err.ec());
+}

test/utils/server_version.hxx

@@ -304,6 +304,11 @@ struct server_version {
     // See MB-63870
     return (major == 7 && minor == 6 && micro >= 4) || (major == 7 && minor > 6) || major > 7;
   }
+
+  [[nodiscard]] auto supports_replace_body_with_xattr() const -> bool
+  {
+    return (major == 7 && minor == 1) || (major == 7 && minor > 1) || major > 7;
+  }
 };
 
 } // namespace test::utils