path_alias can be passed unexpected data types for the path

`$path` is documented as having to be a string. What are the steps to reproduce?

   * @param string $path
   *   The path to process, with a leading slash.

after i change the php version to 8.1 from 7.4, clear the cache, go to content page, and bim....

Deprecated: strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated in /var/www/html/web/core/modules/path_alias/src/PathProcessor/AliasPathProcessor.php on line 54

PHP 8.1 change the game, if a function ask for a string, we have to pass a string, and null is not a string.

The best way is to test the $path variable before use it.

cd : https://php.watch/versions/8.1/internal-func-non-nullable-null-deprecation

Please explain the code path that is sending a null.

I think that's not the point!

The goal is to secure the code, with PHP8.1, only the right type must be passed to a function, that the fact, whatever the way a null came to this function, it is necessary to manage, and anticipate this case, to guarantee to only pass a string type to a function that needs a string type in its declaration. :)

Thank you.

Why not type hint in the function signature?

There may be a misunderstanding.

In core/modules/path_alias/src/PathProcessor/AliasPathProcessor.php

At L54, there is a strpos function, it is a PHP function. This function expects a string in its first parameter.

With PHP8.1 we have to pass a string, and just a string, null is not a string, so you have to secure your code, test the $path variable to be sure it is a string, and nothing other.

So, either test the $path variable before using the strpos function, or cast the $path variable, or do:

strpos($path ?? '', '//')