How to display post content instead of excerpt

If you want to always return post content when trying to get post excerpt, you can use get_the_excerpt filter like this.

add_filter( 'get_the_excerpt', 'wp256_use_content_as_excerpt', 10, 2 );
function wp256_use_content_as_excerpt( $excerpt, $post ) {
    return wp_strip_all_tags( $post->post_content );
}