refactor: correct type mismatch on CommandOptions for writeConcern

src/cmap/wire_protocol/command.ts

@@ -8,6 +8,7 @@ import type { Document, BSONSerializeOptions } from '../../bson';
 import type { Server } from '../../sdam/server';
 import type { Topology } from '../../sdam/topology';
 import type { ReadPreferenceLike } from '../../read_preference';
+import type { WriteConcernOptions, WriteConcern, W } from '../../write_concern';
 
 /** @internal */
 export interface CommandOptions extends BSONSerializeOptions {
@@ -28,6 +29,9 @@ export interface CommandOptions extends BSONSerializeOptions {
   willRetryWrite?: boolean;
   retryWrites?: boolean;
   retrying?: boolean;
+
+  // FIXME: NODE-2781
+  writeConcern?: WriteConcernOptions | WriteConcern | W;
 }
 
 function isClientEncryptionEnabled(server: Server) {

src/sessions.ts

@@ -20,6 +20,7 @@ import type { CommandOptions } from './cmap/wire_protocol/command';
 import type { MongoClientOptions } from './mongo_client';
 import type { Cursor } from './cursor/cursor';
 import type { CoreCursor } from './cursor/core_cursor';
+import type { WriteConcern } from './write_concern';
 const minWireVersionForShardedTransactions = 8;
 
 function assertAlive(session: ClientSession, callback?: Callback): boolean {
@@ -720,7 +721,8 @@ function applySession(
   }
 
   // SPEC-1019: silently ignore explicit session with unacknowledged write for backwards compatibility
-  if (options && options.writeConcern && options.writeConcern.w === 0) {
+  // FIXME: NODE-2781, this check for write concern shouldn't be happening here, but instead during command construction
+  if (options && options.writeConcern && (options.writeConcern as WriteConcern).w === 0) {
     if (session && session.explicit) {
       return new MongoError('Cannot have explicit session with unacknowledged writes');
     }