实现不需要输入密码，仅输入用户名或电子邮件即可登录的表单

<form autocomplete="off" method="post">
    <div class="form-group">
        <input id="userlog" name="userlog" type="text" placeholder="<?php echo esc_attr__('Username/email', 'theme-domain'); ?>" class="form-control" required="required">
    </div>
    <input type="hidden" name="action" value="my_login_action" />
    <button type="submit"><?php echo esc_html__('Login', 'theme-domain'); ?></button>  
</form>

functions.php:

add_action('init', function(){
    // Return if not the login request
    if( !isset( $_POST['action'] ) || $_POST['action'] !== 'my_login_action' )
        return;
    $result;
    $username = $_POST['userlog'];
    if ( ! $result ) {
        $result = get_user_by( 'email', $username ); // user email
    }
    if ( ! $result ) {
        $result = get_user_by('login', $username ); // user name
    }

    if ( !is_wp_error($result) ){
        wp_clear_auth_cookie();
        wp_set_current_user($result->ID);
        wp_set_auth_cookie($result->ID);
        wp_redirect( home_url( '/' ) );
        exit;
    }
    die();
});