fix(NODE-7643): preserve $meta direction in [field, direction] sort pair

src/sort.ts

@@ -81,7 +81,7 @@ function isReadonlyArray<T>(value: any): value is readonly T[] {
 
 /** @internal */
 function pairToMap(v: readonly [string, SortDirection]): SortForCmd {
-  return new Map([[`${v[0]}`, prepareDirection([v[1]])]]);
+  return new Map([[`${v[0]}`, prepareDirection(v[1])]]);
 }
 
 /** @internal */

test/integration/crud/find.test.ts

@@ -884,6 +884,37 @@ describe('Find', function () {
     test.equal('spam eggs and spam', items[0].s);
   });
 
+  it('should correctly sort by text score given as a [field, direction] pair', async function () {
+    const configuration = this.configuration;
+    const db = client.db(configuration.db);
+
+    const collection = db.collection('textSearchWithPairSort');
+    await collection.createIndex({ title: 'text' });
+
+    await collection.insertMany([
+      { title: 'The Godfather Part II' },
+      { title: 'Casablanca' },
+      { title: 'Harlem Nights' },
+      { title: 'The Godfather' },
+      { title: 'Godfather of Harlem' }
+    ]);
+
+    const items = await collection
+      .find(
+        { $text: { $search: 'godfather harlem' } },
+        { projection: { _id: false, title: true, score: { $meta: 'textScore' } } }
+      )
+      .sort(['score', { $meta: 'textScore' }])
+      .toArray();
+
+    expect(items.map(({ title }) => title)).to.deep.equal([
+      'Godfather of Harlem',
+      'The Godfather',
+      'Harlem Nights',
+      'The Godfather Part II'
+    ]);
+  });
+
   it('should not mutate user-provided options', async function () {
     const configuration = this.configuration;
     const db = client.db(configuration.db);

test/unit/sort.test.ts

@@ -0,0 +1,21 @@
+import { expect } from 'chai';
+
+import { formatSort } from '../mongodb';
+
+describe('formatSort', function () {
+  context('when the sort is a [field, direction] pair', function () {
+    it('formats a numeric direction', function () {
+      expect(formatSort(['alpha', -1])).to.deep.equal(new Map([['alpha', -1]]));
+    });
+
+    it('formats a string direction', function () {
+      expect(formatSort(['alpha', 'asc'])).to.deep.equal(new Map([['alpha', 1]]));
+    });
+
+    it('preserves a $meta direction', function () {
+      expect(formatSort(['alpha', { $meta: 'textScore' }])).to.deep.equal(
+        new Map([['alpha', { $meta: 'textScore' }]])
+      );
+    });
+  });
+});