Theme suggestions for blocks in a region which has a dash in the name I have a Region in the theme called header-top. As you may notice this region has a dash in the name instead of an underscore.

This theme is a sub-theme of a master theme called Framework. I wanted to apply a certain template file to blocks in that region, so according to Drupal 7 Theme Hook Suggestions page I've created a template file called block--header-top.tpl.php and cleared the cache. After re-loading the page a few times, I inspect the HTML to see if this particular template file is being applied, but all evidence suggests that it's still using block.tpl.php. I've tried using template_preprocess_block and dpm-ing out the $variables and in there I see an array theme_hook_suggestions which has the following values: array(block__header-top, block__block, block__block__21). I've checked the existing template files and there's no template file named block--block.tpl.php or block--block--21.tpl.php. I've even tried to swap the dash with an underscore to be block--header_top.tpl.php but still no luck.

Finally I've switched the region name to become header_top and the renamed template block--header_top.tpl.php suddenly starts to take effect.

I'm wondering is there a certain naming convention for regions with dashes in the name? If so what would be the ways to try and find out what exactly the template name for this region should be? I'd like to not resort to renaming the region, as that may have a knock-on effect on modules and other template files which I may miss and mess up the production website.
Per the Theme suggestion docs you linked to the format for region-specific block templates go like this:


  An example of a region-specific template would be "block--sidebar_first.tpl.php"


It looks like Drupal flips _ and - in theme suggestions so 


  block__header-top


becomes


  block--header_top.tpl.php


(I knew it replaced _ with - but I didn't know it was the other way round too; there may be more to it than that).