将上述所有代码替换为以下代码：

<?php

function master_load_ads_txt_template_include( $template ) {
    $is_load_ads_txt = (bool) get_query_var( \'ads-txt\' );

    if ( $is_load_ads_txt ) {
        $template = locate_template( \'template-parts/ads-txt.php\' );
    }

    return $template;
}

add_filter( \'template_include\', \'master_load_ads_txt_template_include\' );

function master_load_ads_txt_rewrite() {
    add_rewrite_rule( \'ads.txt\', \'index.php?ads-txt=true\', \'top\' );

    // The line below doesn\'t work and it\'s useless.
    // add_rewrite_rule( \'^ads.txt/\', \'ads.txt\', \'top\' );
}

add_action( \'init\', \'master_load_ads_txt_rewrite\' );

function master_load_ads_txt_query_vars( $query_vars ) {
    $query_vars[] = \'ads-txt\';

    return $query_vars;
}

add_filter( \'query_vars\', \'master_load_ads_txt_query_vars\' );

function redirect_canonical_callback( $redirect_url, $requested_url ) {
    $is_load_ads_txt = (bool) get_query_var( \'ads-txt\' );

    if ( $is_load_ads_txt ) {
        return $requested_url;
    }

    return $redirect_url;
}

add_filter( \'redirect_canonical\', \'redirect_canonical_callback\', 100, 2 );

A few notes:

1. template_include 是过滤器挂钩，而不是动作挂钩。它是固定的add_rewrite_rule(\'^ads.txt/\', \'ads.txt\', \'top\'); 是无用的。它是固定的redirect_canonical 应在过滤器挂钩中使用，而不是在操作中使用functions.php 文件不要忘记通过访问Settings > Permalinks.

/* ORIGINAL CODE */
function master_load_ads_txt_template_include($template) {
    $is_load_ads_txt = (bool)get_query_var(\'ads-txt\');
    if( $is_load_ads_txt ) {
        $template = get_template_part("template-parts/ads-txt");
    }
    return $template;
}
add_action( \'template_include\', \'master_load_ads_txt_template_include\' );

function master_load_ads_txt_rewrite() {
    /* UPDATE RULE */
    add_rewrite_rule(\'^ads.txt$\', \'index.php?ads-txt=true\', \'top\');
}
add_action(\'init\', \'master_load_ads_txt_rewrite\');

function master_load_ads_txt_query_vars( $query_vars ) {
    $query_vars[] = \'ads-txt\';
    return $query_vars;
}
add_filter( \'query_vars\', \'master_load_ads_txt_query_vars\');

/* ACTION TO ALLOW URL WITHOUT LAST TRAILING SLASH */
function disable_canonical_redirects_for_ads_txt( $redirect_url, $requested_url ) {
    if ( preg_match( \'|ads\\.txt|\', $requested_url ) ) {
        return $requested_url;
    }
    return $redirect_url;
}
add_action( \'redirect_canonical\', \'disable_canonical_redirects_for_ads_txt\', 10, 2 );