[wp-trac] [WordPress Trac] #43489: Strengthen resilience of wp_register_plugin_realpath to support Gutenberg

[WordPress Trac]

#43489: Strengthen resilience of wp_register_plugin_realpath to support Gutenberg
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 Reporter:  bobbingwide   |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  General       |    Version:  trunk
 Severity:  normal        |   Keywords:
  Focuses:                |
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 For many years now I've been working in a Windows development environment
 with multiple subdirectory installs referencing plugins using symlinks.

 Every now and then I get problems due to plugin files apparently not being
 present when they quite clearly are. I have not been able to track it
 down. I think it's a bug in PHP associated with OpCache.

 Anyway, the bottom line is that sometimes this problem, or something
 similar, results in the `$wp_plugin_paths` array containing entries with a
 null value for `$realdir`.

 This can lead to the following:

 Warning: strpos(): Empty needle in C:\apache\htdocs\hm\wp-
 includes\plugin.php on line 658.

 This message has the uncanny knack of happening at the most inappropriate
 times.

 Now, with Gutenberg looming, the problem is further reducing my ability to
 create content locally; Gutenberg can't handle the unexpected Warnings and
 Notices from a development server and fails. See
 https://github.com/WordPress/gutenberg/issues/5439

 To reduce the likelihood of the problem I'd like to propose a change to
 `wp_register_plugin_path()` to cater for a false value being returned from
 the `realpath()` PHP function.

 The proposal being that if `$plugin_realpath` does appear to be null, then
 don't add an entry in `$wp_plugin_paths`.

 This change will prevent the warning message being issued from
 plugin_basename()'s test
 ```
 if ( strpos( $file, $realdir ) === 0 ) {
 ```

 and therefore increases the robustness of the system.

 Bottom line.
 - realpath() may return false.
 - This should be catered for.

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Ticket URL: <https://core.trac.wordpress.org/ticket/43489>
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