fix(NODE-4186): accept ReadPreferenceLike in TransactionOptions type

src/transactions.ts

@@ -2,6 +2,7 @@ import type { Document } from './bson';
 import { MongoRuntimeError, MongoTransactionError } from './error';
 import type { CommandOperationOptions } from './operations/command';
 import { ReadConcern, ReadConcernLike } from './read_concern';
+import type { ReadPreferenceLike } from './read_preference';
 import { ReadPreference } from './read_preference';
 import type { Server } from './sdam/server';
 import { WriteConcern } from './write_concern';
@@ -67,7 +68,7 @@ export interface TransactionOptions extends CommandOperationOptions {
   /** A default writeConcern for commands in this transaction */
   writeConcern?: WriteConcern;
   /** A default read preference for commands in this transaction */
-  readPreference?: ReadPreference;
+  readPreference?: ReadPreferenceLike;
   /** Specifies the maximum amount of time to allow a commit action on a transaction to run in milliseconds */
   maxCommitTimeMS?: number;
 }

test/types/community/transaction.test-d.ts

@@ -48,6 +48,7 @@ async function runTransactionWithRetry(
 
 async function updateEmployeeInfo(client: MongoClient, session: ClientSession) {
   session.startTransaction({
+    readPreference: 'primary',
     readConcern: new ReadConcern('available'), // NODE-3297
     writeConcern: { w: 'majority' }
   });

test/unit/transactions.test.ts

@@ -0,0 +1,28 @@
+import { expect } from 'chai';
+
+import { ReadPreference } from '../../src';
+import { Transaction } from '../../src/transactions';
+
+describe('class Transaction', () => {
+  describe('constructor()', () => {
+    it('uses ReadPreference instance', () => {
+      const transaction = new Transaction({
+        readPreference: ReadPreference.nearest
+      });
+      expect(transaction.options)
+        .to.have.property('readPreference')
+        .that.is.instanceOf(ReadPreference)
+        .that.has.property('mode', 'nearest');
+    });
+
+    it('transforms ReadPreferenceLike string', () => {
+      const transaction = new Transaction({
+        readPreference: 'nearest'
+      });
+      expect(transaction.options)
+        .to.have.property('readPreference')
+        .that.is.instanceOf(ReadPreference)
+        .that.has.property('mode', 'nearest');
+    });
+  });
+});