Custom Taxonomy template not display

Question

I am having problem when I want to display my taxonomy template.
I have created one custom taxonomy 'Location' for my custom post type 'Project'. Moreover, I have created templates for it as :

taxonomy-{taxonomy_name}-{term}.php
taxonomy-{taxonomy_name}.php
taxonomy.php

None of them work... I just get my archive-{post_type}.php in all case.

My targetted URLs are :
mywebsite.com/holliday/united-kingdom/ (Location taxonomy)
mywebsite.com/holliday/united-kingdom/london (Location taxonomy child)

I should have messed up or missed something when creating my taxonomy but can't get it right.

Here is my code (register post type and register taxonomy) :

// Register Post Type (Holliday)
$capability = 'publish_posts';

$cpt_args = array(
    'menu_icon'         => 'dashicons-groups',
    'labels'            => array(
        'name'              => __( 'Holliday', 'mon-plugin' ),
        'singular_name'     => __( 'Holliday', 'mon-plugin' ),
        'add_new'           => __( 'Add Holliday', 'mon-plugin' ),
        'add_new_item'      => __( 'Add Holliday', 'mon-plugin' ),
        'edit'              => __( 'Edit', 'mon-plugin' ),
        'edit_item'         => __( 'Edit Holliday', 'mon-plugin' ),
        'new_item'          => __( 'New Holliday', 'mon-plugin' ),
        'view'              => __( 'View Holliday', 'mon-plugin' ),
        'view_item'         => __( 'View Holliday', 'mon-plugin' ),
        'search_items'      => __( 'Search Holliday', 'mon-plugin' ),
        'not_found'         => __( 'No Holliday found', 'mon-plugin' ),
        'not_found_in_trash'=> __( 'No Holliday found in Trash', 'mon-plugin' ),
        'parent'            => __( 'Parent Holliday', 'mon-plugin' ),
    ),
    'public'            => true,
    'has_archive'       => true,
    'rewrite'           => array(
        'slug'              => 'holliday/%my_project_location%',
    ),
    'supports'          => array('title', 'custom-fields', 'excerpt', 'editor', 'author', 'thumbnail', 'comments'),
    'capabilities'      => array(
        'publish_posts'     => $capability,
        'edit_posts'        => $capability,
        'edit_others_posts' => $capability,
        'delete_posts'      => $capability,
        'delete_others_posts'=> $capability,
        'read_private_posts'=> $capability,
        'edit_post'         => $capability,
        'delete_post'       => $capability,
        'read_post'         => $capability
    ),
);
register_post_type( 'my_project', $cpt_args );

// Register Taxonomy (Location)
$cats_args = array( 
    'labels'            => array(
        'name'              => _x( 'Project Location', 'mon-plugin' ),
        'singular_name'     => _x( 'Location', 'mon-plugin' ),
        'search_items'      => __( 'Search Location', 'mon-plugin' ),
        'all_items'         => __( 'All Location', 'mon-plugin' ),
        'parent_item'       => __( 'Parent Location', 'mon-plugin' ),
        'parent_item_colon' => __( 'Parent Location:', 'mon-plugin' ),
        'edit_item'         => __( 'Edit Location', 'mon-plugin' ),
        'update_item'       => __( 'Update Location', 'mon-plugin' ),
        'add_new_item'      => __( 'Add New Location', 'mon-plugin' ),
        'new_item_name'     => __( 'New Location Name', 'mon-plugin' ),
        'menu_name'         => __( 'Location', 'mon-plugin' ),
    ),
    'hierarchical'      => true,
    'public'            => true,
    'show_ui'           => true,
    'has_archive'       => true,
    'rewrite'           => array(
        'slug'              => 'holliday',
        'hierarchical'      => true
    )
);
register_taxonomy( 'my_project_location', 'my_project', $cats_args );

EDIT:
If I change my taxonomy slug into something else, I get my taxonomy template working.
Example:

 taxonomy slug => "location"  
 mywebsite.com/location/united-kingdom/ => Taxonomy template working !  

But I want my taxonomy to work with my custom post type. To get my taxonomy template when accessing mywebsite.com/{custom-post-type}/{taxonomy}/
But this give me archive-{custom-post-type}.php file instead.

Following the Template Hierarchy I expect Wordpress to find me the taxonomy template before the archive template.

Is there something I am missing ?
Thank you for your help.

Answer 1

There are a couple of different solutions if you want to have only the /holliday/project-location/ URL and not separate archive and taxonomy URLs.

Option 1:

Use the template_include() filter. I think this code would work but have not tested:

add_filter( 'template_include', 'holliday_template', 99 );

function holliday_template( $template ) {

    if ( is_post_type_archive( 'holliday' )  ) {
        $new_template = locate_template( array( 'taxonomy-my_project_location.php' ) );
        if ( '' != $new_template ) {
            return $new_template;
        }
    }

    return $template;
}

Option 2 (even simpler):

Tell WP not to give your holliday CPT an archive. When you register the post type, just change 'has_archive' => true, to false. That way, when WP looks for content at your desired URL, only the taxonomy archive exists. You will most likely need to use unregister_post_type() and re-register it to force the change.

Answer 2

Thank you WebElaine for your help ! I figured out a way to solve it.

It looks a bit as you proposed in Option 2. Except that I used the filter parse_query to change my CPT 'has_archive' to false when accessing my taxonomy.

Here is the code :

function check_taxonomy_query( $query ) {
    if ($query->query['my_project_location'] && !$query->query['my_project']) {
        $query->is_post_type_archive = false;
    }
}
add_action( 'parse_query', 'check_taxonomy_query' );  

my_project_location and my_project are the query vars used for my rewrite rules:

$newRules['holliday/?$']    =   'index.php?lang=en&post_type=my_project';
$newRules['holliday/([^/]+)/?$']    =   'index.php?lang=en&post_type=my_project&my_project_location=$matches[1]';
$newRules['holliday/([^/]+)/([^/]+)/?$']    =   'index.php?lang=en&post_type=my_project&my_project_location=$matches[1]/$matches[2]';
$newRules['holliday/([^/]+)/([^/]+)/([^/]+)/?$']    =   'index.php?lang=en&post_type=my_project&my_project_location=$matches[1]/$matches[2]&my_project=$matches[3]';

So in the check_taxonomy_query function, I simply check if I am in the case of the 2nd or 3rd line of my rewrite rules. If yes, I turn the post type archive down.

Hope it could help someone ;)