themes.php doesn't show themes if using Mac-style CR EOL markers

[novasource]

Apparently Macs by default only use CRs to mark end of lines.

If a child theme's style.css file was saved using this, which can happen in Dreamweaver, WordPress won't even show the child theme at wp-admin/themes.php. This has come up at ​http://wordpress.org/support/topic/child-themes-doesnt-show-up-in-mamp.

If EOL only with CR isn't supported, it would be nice to at least show a warning.

This happens with plugins also.

Tracked it down to the regex in get_file_data(). The line start/end metacharacters (^ and $) require a LF (\n) in order to detect the start/end of a line - which of course isn't there if you just have CR (\r). Fix seems relatively simple.

Make sure we have preg-compatible EOLs

The lookahead in the first patch was faulty

This probably also works:

$file_data = str_replace( array( "\r\n", "\r" ), "\n", $file_data );

Indeed, that is much more efficient. Patch updated.

nacin's fix

Closed #20248 as duplicate

No need to even replace \r\n; we just need to replace \r with \n. If an \r\n becomes \n\n, the function will still end up with the right data.

Added test cases in ​[UT703].

In [20640]:

Properly extract file headers via get_file_data() when CR line endings are used. props solarissmoke for the initial patch. fixes #19854.