Conditional tags don't work within add_feed() callback function

[sanchothefat]

I was putting together a custom feed and wanted to pick a different template based on the context of where I was in the site. So for example I wanted one feed template on the home/front page and another for category pages.

Using add_feed() and browsing to that feed results in only is_feed() being true and not any of the other conditional tags.

I was wondering if a) there's a reason for that and b) if it's something we could fix.

I'm not entirely sure where to look though. Attempts at running $wp_query->parse_query_vars() to force the conditionals to be set were unsuccessful.

The following code is a quick demo:

add_feed( 'new_feed', 'feed_output' );

function feed_output() {
    if ( is_home() )
        echo 'home feed';
    if ( is_singular() )
        echo 'singular feed';
    if ( is_category() )
        echo 'category feed';
}

Nothing will be output on /feed/new_feed/ URLs even if on home, single or category page.

It doesn't make sense to return true for is_home or is_singular in a feed. It's a feed so is_feed returns true. You need to define your own query for the feed content.

Example:

add_feed( 'my-feed', 'my_feed_template' );

function feed_template() {
	load_template( ABSPATH . WPINC . '/feed-rss2.php' );
}

add_action( 'pre_get_posts', 'my_feed_content' );
function feed_content( $query ) {
	// Bail if $posts_query is not an object or of incorrect class
	if ( ! is_object( $query ) || ( 'WP_Query' != get_class( $query ) ) )
		return;

	// Bail if filters are suppressed on this query
	if ( $query->get( 'suppress_filters' ) )
		return;

	if ( ! $query->is_feed( 'my-feed' ) )
		return;

	$query->set( 'post_type', array( 'post', 'page' ) );
}

@ocean90 I get what you're saying. Thing is though feeds change depending on context eg. /category/cat-name/feed/ is a feed for that category, so wouldn't it be useful to have a way of telling them apart from the main feed for example?

What about feed versions of the is_category() type conditionals eg. something like is_category_feed(), is_tax_feed() etc...?

My use case for this was generating alternate views of the same context for a WordPress to kindle feed.

Duplicate of #20899.