Unit tests that confirm that the original image is properly converted to additional mime type

src/wp-admin/includes/image.php

@@ -341,6 +341,18 @@ function wp_create_image_subsizes( $file, $attachment_id ) {
 				 */
 				if ( $scale_down ) {
 					$saved = $editor->save( $editor->generate_filename( 'scaled' ) );
+				} elseif ( $convert ) {
+					/*
+					 * Generate a new file name for the converted image.
+					 *
+					 * As the image file name will be unique due to the changed file extension,
+					 * it does not need a suffix to be unique. However, the generate_filename method
+					 * does not allow for an empty suffix, so the "-converted" suffix is required to
+					 * be added and subsequently removed.
+					 */
+					$converted_file_name = $editor->generate_filename( 'converted' );
+					$converted_file_name = preg_replace( '/(-converted\.)([a-z0-9]+)$/i', '.$2', $converted_file_name );
+					$saved = $editor->save( $converted_file_name );
 				} else {
 					$saved = $editor->save();
 				}

tests/phpunit/tests/media.php

@@ -6445,6 +6445,59 @@ public function test_wp_img_tag_add_auto_sizes( string $input, string $expected
 		);
 	}
 
+	/**
+	 * @ticket 62305
+	 *
+	 * @dataProvider data_image_converted_to_other_format_has_correct_filename
+	 *
+	 * @param bool $apply_big_image_size_threshold True if filter needs to apply, otherwise false.
+	 */
+	public function test_image_converted_to_other_format_has_correct_filename( bool $apply_big_image_size_threshold ) {
+		$temp_dir      = get_temp_dir();
+		$file          = $temp_dir . '/33772.jpg';
+		$scaled_suffix = $apply_big_image_size_threshold ? '-scaled' : '';
+		copy( DIR_TESTDATA . '/images/33772.jpg', $file );
+
+		$editor = wp_get_image_editor( $file );
+
+		// Verify that the selected editor supports WebP output.
+		if ( is_wp_error( $editor ) || ! $editor->supports_mime_type( 'image/webp' ) ) {
+			$this->markTestSkipped( 'WebP is not supported by the selected image editor.' );
+		}
+
+		$attachment_id = self::factory()->attachment->create_object(
+			array(
+				'post_mime_type' => 'image/jpeg',
+				'file'           => $file,
+			)
+		);
+
+		if ( $apply_big_image_size_threshold ) {
+			add_filter( 'big_image_size_threshold', array( $this, 'add_big_image_size_threshold' ) );
+		}
+
+		// Generate all sizes as WebP.
+		add_filter( 'image_editor_output_format', array( $this, 'image_editor_output_webp' ) );
+
+		$image_meta = wp_generate_attachment_metadata( $attachment_id, $file );
+
+		$this->assertStringEndsNotWith( '.jpg', $image_meta['file'], 'The file extension is expected to change.' );
+		$this->assertSame( "33772{$scaled_suffix}.webp", basename( $image_meta['file'] ), 'The file name is expected to be 33772.webp' );
+		$this->assertSame( '33772.jpg', $image_meta['original_image'], 'The original image name is expected to be stored in the meta data' );
+	}
+
+	/**
+	 * Data provider for test_image_metadata_get_converted_image_in_file_key().
+	 *
+	 * @return array[]
+	 */
+	public function data_image_converted_to_other_format_has_correct_filename() {
+		return array(
+			'do not scale image' => array( false ),
+			'scale image'        => array( true ),
+		);
+	}
+
 	/**
 	 * Helper method to keep track of the last context returned by the 'wp_get_attachment_image_context' filter.
 	 *