[wp-trac] [WordPress Trac] #57375: Add move_dir() function

[WordPress Trac]

#57375: Add move_dir() function
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 Reporter:  afragen         |       Owner:  (none)
     Type:  enhancement     |      Status:  new
 Priority:  normal          |   Milestone:  6.2
Component:  Filesystem API  |     Version:  trunk
 Severity:  normal          |  Resolution:
 Keywords:  has-patch       |     Focuses:  performance
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Comment (by costdev):

 Some additional information:

 == WP_Filesystem_* classes
 `WP_Filesystem_Direct::move()` and the other filesystem `::move()` methods
 are documented to move a file, not to move a directory. For non-direct
 filesystems, the moving of directories is a happy extra due to the
 behaviour of FTP/SSH functions.

 == WP_Filesystem_Direct::move()
 While `WP_Filesystem_Direct::move()` uses `rename()`, which works for
 files ''and'' directories, if `rename()` should fail, it falls back to a
 `copy()`, a single-file function.

 == How should a `move_dir()` function differ?
 It makes sense to introduce a `move_dir()` function that uses
 `$wp_filesystem->move()` for non-direct filesystems, and `rename()` with a
 fallback to `copy_dir()` for the direct filesystem.

 == Performance
 In terms of memory usage and speed, a recursive copy involves the
 ''contents'' of the files/directories, including calls to `mkdir()`, and a
 subsequent `unlink()`.

 `rename()`, on the other hand, simply updates the ''metadata''. This makes
 `rename()` significantly more performant. It is purpose-built for moving
 files and directories.

 == PHP's `rename()` under the hood
 As mentioned above, `rename()` updates the ''metadata''. However, when
 PHP's `rename( $from, $to )` is called with `$from` and `$to` on different
 drives, it uses a recursive copy. For anyone who has ever dragged and
 dropped a file/directory from one drive to another, you'll likely have
 noticed that this makes a copy on the second drive. This isn't a negative,
 but just a bit of extra information on how `rename()` handles this
 scenario for those interested.

 -----

 Overall, a +1 from me on implementing a function for the performant and
 recursive moving of directories.

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Ticket URL: <https://core.trac.wordpress.org/ticket/57375#comment:2>
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