Error in WordPress with plugin reactpress - php

Question

I'm using WordPress version 5.7.2 and when I upgrade it to php version 7.4.19 I get these errors:
Failed opening 'default' for inclusion (include_path='.:/usr/lib/php7.4') wp-includes/template-loader.php on line 106
Warning: include(default): failed to open stream: No such file or directory in /homepages/1/d229455270/htdocs/clickandbuilds/WordPress/DaseCMS/wp-includes/template-loader.php on line 106
This happens when I activate the plugin reactpress. This is the piece of code where the error occurs:
/**
* Filters the path of the current template before including it.
*
* #since 3.0.0
*
* #param string $template The path of the template to include.
*/
$template = apply_filters( 'template_include', $template );
if ( $template ) {
include $template; //Error in this line
} elseif ( current_user_can( 'switch_themes' ) ) {
$theme = wp_get_theme();
if ( $theme->errors() ) {
wp_die( $theme->errors() );
}
Why is this happening? How can I fix it? I see that is compatible with my WordPress version...
And with my php version...
Thank you in advance

Answer 1

Why is this happening?
Because there's a mistake in the Reactpress_Public::repr_change_page_template() method (see line 99 in wp-content/plugins/reactpress/public/class-reactpress-public.php) which is hooked onto template_include.
The author should check if the value of the _wp_page_template metadata (which stores the path of a custom page template) is not default (which is the default value) and only if so, then should the $template value be set to the metadata value.
And if one doesn't do that check, then we'd end up with include 'default' which then emits the error/warning in question ("Failed opening 'default' for inclusion").
How can I fix it?
Please contact the plugin support and ask them to fix the issue ASAP, but for the time being, you may just change the conditional here to: (* change the entire "if")
if (!empty($meta['_wp_page_template'][0]) && $meta['_wp_page_template'][0] != $template && // wrapped
'default' !== $meta['_wp_page_template'][0] // check if the value is NOT "default"
) {
$template = $meta['_wp_page_template'][0];
}
Yes, you shouldn't modify core plugin files; but this is a special case, because the plugin needs a fix, which hopefully will come in the plugin's next release.
Alternate solution without modifying the plugin files
.. is by overriding the template using the same hook:
// Add to the theme functions.php file:
add_filter( 'template_include', 'my_fix_template_include', 100 );
function my_fix_template_include( $template ) {
if ( 'default' === $template && is_page() ) { // * the plugin uses is_page()
$template = get_page_template();
}
return $template;
}