BUG: Array to String conversion when using Requirements::combine_files with path/type arguments

[nicole-ashley]

When using Requirements with files whose type needs to be specified manually (eg, their extension is not 'js' or 'css'), the combine_files duplicate check throws a notice because array_intersect casts the array values to string.

Requirements::combine_files('out.min.js', array(
    array('path' => 'themes/mytheme/js/library.js.inc', 'type' => 'js')
);

The example is arbitrary; going by the above I could just rename the file, but in my real-world case I'm dealing with scripts in other languages which are compiled on load. These scripts have suffixes which shouldn't be changed.

// Requirements_Backend::combine_files
public function combine_files($combinedFileName, $files, $media = null) {
    // duplicate check
    foreach($this->combine_files as $_combinedFileName => $_files) {
        $duplicates = array_intersect($_files, $files); // -- HERE --
        if($duplicates && $combinedFileName != $_combinedFileName) {
            user_error("Requirements_Backend::combine_files(): Already included files " . implode(',', $duplicates)
                . " in combined file '{$_combinedFileName}'", E_USER_NOTICE);
            return false;
        }
    }
    ...
}

As array_intersect casts to string, it's casting the input array (and potentially any of these arrays that wind up in combine_files in future checks), causing the warning to be thrown and the comparison fail.

[tractorcow]

The parseCombinedFile() method addresses this issue.