Add $replaceWith stage to aggregation pipeline builder

lib/Doctrine/ODM/MongoDB/Aggregation/Builder.php

@@ -518,6 +518,27 @@ public function replaceRoot($expression = null): Stage\ReplaceRoot
         return $stage;
     }
 
+    /**
+     * Replaces the input document with the specified document. The operation
+     * replaces all existing fields in the input document, including the _id
+     * field. With $replaceWith, you can promote an embedded document to the
+     * top-level. You can also specify a new document as the replacement.
+     *
+     * The $replaceWith stage is an alias for $replaceRoot.
+     *
+     * @see https://www.mongodb.com/docs/rapid/reference/operator/aggregation/replaceWith/
+     *
+     * @param string|mixed[]|Expr|null $expression Optional. A replacement expression that
+     * resolves to a document.
+     */
+    public function replaceWith($expression = null): Stage\ReplaceWith
+    {
+        $stage = new Stage\ReplaceWith($this, $this->dm, $this->class, $expression);
+        $this->addStage($stage);
+
+        return $stage;
+    }
+
     /**
      * Controls if resulting iterator should be wrapped with CachingIterator.
      */

lib/Doctrine/ODM/MongoDB/Aggregation/Stage.php

@@ -323,6 +323,24 @@ public function replaceRoot($expression = null): Stage\ReplaceRoot
         return $this->builder->replaceRoot($expression);
     }
 
+    /**
+     * Replaces the input document with the specified document. The operation
+     * replaces all existing fields in the input document, including the _id
+     * field. With $replaceWith, you can promote an embedded document to the
+     * top-level. You can also specify a new document as the replacement.
+     *
+     * The $replaceWith stage is an alias for $replaceRoot.
+     *
+     * @see https://www.mongodb.com/docs/rapid/reference/operator/aggregation/replaceWith/
+     *
+     * @param string|mixed[]|Expr|null $expression Optional. A replacement expression that
+     * resolves to a document.
+     */
+    public function replaceWith($expression = null): Stage\ReplaceWith
+    {
+        return $this->builder->replaceWith($expression);
+    }
+
     /**
      * Controls if resulting iterator should be wrapped with CachingIterator.
      */

lib/Doctrine/ODM/MongoDB/Aggregation/Stage/ReplaceWith.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\ODM\MongoDB\Aggregation\Stage;
+
+class ReplaceWith extends ReplaceRoot
+{
+    public function getExpression(): array
+    {
+        $expression = parent::getExpression();
+
+        return [
+            '$replaceWith' => $expression['$replaceRoot']['newRoot'],
+        ];
+    }
+}

tests/Doctrine/ODM/MongoDB/Tests/Aggregation/Stage/ReplaceWithTest.php

@@ -0,0 +1,90 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\ODM\MongoDB\Tests\Aggregation\Stage;
+
+use DateTimeImmutable;
+use Doctrine\ODM\MongoDB\Tests\BaseTest;
+use Documents\CmsComment;
+use Documents\User;
+use MongoDB\BSON\UTCDateTime;
+
+class ReplaceWithTest extends BaseTest
+{
+    public function testTypeConversion(): void
+    {
+        $builder = $this->dm->createAggregationBuilder(User::class);
+
+        $dateTime  = new DateTimeImmutable('2000-01-01T00:00Z');
+        $mongoDate = new UTCDateTime((int) $dateTime->format('Uv'));
+        $stage     = $builder
+            ->replaceWith()
+                ->field('isToday')
+                ->eq('$createdAt', $dateTime);
+
+        self::assertEquals(
+            [
+                '$replaceWith' => (object) [
+                    'isToday' => ['$eq' => ['$createdAt', $mongoDate]],
+                ],
+            ],
+            $stage->getExpression(),
+        );
+    }
+
+    public function testTypeConversionWithDirectExpression(): void
+    {
+        $builder = $this->dm->createAggregationBuilder(User::class);
+
+        $dateTime  = new DateTimeImmutable('2000-01-01T00:00Z');
+        $mongoDate = new UTCDateTime((int) $dateTime->format('Uv'));
+        $stage     = $builder
+            ->replaceWith(
+                $builder->expr()
+                    ->field('isToday')
+                    ->eq('$createdAt', $dateTime),
+            );
+
+        self::assertEquals(
+            [
+                '$replaceWith' => (object) [
+                    'isToday' => ['$eq' => ['$createdAt', $mongoDate]],
+                ],
+            ],
+            $stage->getExpression(),
+        );
+    }
+
+    public function testFieldNameConversion(): void
+    {
+        $builder = $this->dm->createAggregationBuilder(CmsComment::class);
+
+        $stage = $builder
+            ->replaceWith()
+                ->field('someField')
+                ->concat('$authorIp', 'foo');
+
+        self::assertEquals(
+            [
+                '$replaceWith' => (object) [
+                    'someField' => ['$concat' => ['$ip', 'foo']],
+                ],
+            ],
+            $stage->getExpression(),
+        );
+    }
+
+    public function testFieldNameConversionWithDirectExpression(): void
+    {
+        $builder = $this->dm->createAggregationBuilder(CmsComment::class);
+
+        $stage = $builder
+            ->replaceWith('$authorIp');
+
+        self::assertEquals(
+            ['$replaceWith' => '$ip'],
+            $stage->getExpression(),
+        );
+    }
+}