You have a syntax-ish error, or a spelling one. There is a space after “taxonomy” in your tax_query
array. If that were the sum of it I’d have just posted a comment, but additionally that $query->tax_query->queries[] = $workspace_taxonomy_query;
line is pointless. Nothing changes with or without it. Don’t try to hack the array like that. Just use $query->set( 'tax_query', $workspace_taxonomy_query);
as below (using a taxonomy and term that exists in my test environment):
// Add custom posts to main query (archive and home)
add_action( 'pre_get_posts', 'add_post_types_to_query' );
function add_post_types_to_query( $query ) {
if ( (is_home() || is_category() || is_search()) && $query->is_main_query() && !is_admin() )
{
// Query all posts on index and category pages
$query->set( 'post_type', array( 'post', 'page', 'definition', 'video', 'data_vizualization', 'quizz', 'talk', 'question', 'study', 'bibliography' ) );
$workspace_taxonomy_query =
array(
array(
'taxonomy' => 'post_tag',
'field' => 'slug',
'terms' => array('test-4'),
'operator' => 'IN'
)
);
$query->tax_query->queries[] = $workspace_taxonomy_query;
}
return $query;
}