Add simple Twig mechanism to check if media thumbnail file is provided

[hughbris]

I want to determine simply if an image thumbnail file has been provided following the filename pattern [image-name].[extension].thumb.[ext] described in Thumbnail Location, item 1.

I have found that the expression image.items.thumbnails.page is defined happens to tell me if the thumbnail file is provided, but this isn't obvious or elegant.

Maybe a separate issue: I expected [image].thumbnail('page') in Twig to return null or be undefined when a thumbnail file isn't provided, and that would have been the obvious test. However, I noticed that the expression [image].thumbnail('page').display('thumbnail').html falls back to the same as [image].thumbnail('media').display('thumbnail').html in those cases. Whether intended behaviour or not, for me it's not a helpful fallback and not intuitive.

So, to simplify, possibly 2 things to investigate:

• an official/idiomatic Twig function or mechanism to detect presence of thumbnail file
• [image].thumbnail('page').display('thumbnail').html shouldn't fall back to the image medium's HTML when a thumbnail file isn't provided

[rhukster]

I think that it's actually better to have a method on the media object to tell if a thumbnail exists.. This might be buried in there already, need to look.

[hughbris]

Sure, you could sidestep the second issue by testing the first, but only as long as you are aware of the second issue behaviour. I think the second may trip a few up, however.

Thanks, look forward to the results of investigating :)

[rhukster]

Added new method for next release to check for thumbnail.

regarding issue #2, i don't want to change this behavior at this point as people might be depending on it (accidentally or intentionally). Something for Grav 2.0 to improve.