Ads doesn't set status code for ads.txt

[hastinbe]

Steps to reproduce the issue

1. Enable Ads under Traffic
2. Request domain.com/ads.txt
3. Content for the ads.txt is returned but the status code is 404

What I expected

The ads.txt data and an HTTP 200 status code.

What happened instead

The ads.txt data was returned in the response body but the HTTP status code is 404, which was set by the web server because a physical ads.txt did not exist.

The response will be ignored and the file will be considered non-existent by Google's crawler if the response code is not a 200.

[htdat]

Just for ref, I've noticed two users with this issue:

2515605-zen - ads do not display
2541726-zen - ads earning got affected

Internal discussion: p1575611498410900-slack-jetpack-crew

[htdat]

I've updated two tickets above and asked them to use this snippet (created by @zinigor).

When JP 8.1 is released, this snippet should be removed.

Note: we recommend following this guide to add snippets https://jetpack.com/support/adding-code-snippets/

function jetpack_filter_ads_txt_status_header( $string, $code, $description, $protocol ) {

	// Only running on URLs that end on /ads.txt
	if (
		! isset( $_SERVER )
		|| ! isset( $_SERVER['REQUEST_URI'] )
		|| false === strpos( '/ads.txt', $_SERVER['REQUEST_URI'], -8 )
	) {
		return $string;
	}
	return sprintf( "%s 200 OK", $protocol );
}
add_filter( 'status_header', 'jetpack_filter_ads_txt_status_header', 10, 4 );