Fix Mounter.blank? method

[Bonias]

No description provided.

[bensie]

@Bonias Can you explain this change?

[Bonias]

I just wanted to point out that blank? method is currently broken and tests don't cover it, but I'm not sure that my changes are proper way to fix it or test it.

How it is working now:

@instance.image = nil
@instance.image? # => true

What I expect:

@instance.image = nil
@instance.image? # => false

Looks like problem was introduced here e38789c#diff-bff15cc47155b179e2ad618ed40ebbe2L92. Earlier uploader.blank? was called, which was defined as file.blank?, so we were checking if uploader had file assigned. At current implementation uploaders.empty? (Array#empty?) method is used. This mean that true (wrongly) would be returned when uploaders includes only one uploader without a file.

Why current tests does not cover it?

When expect(@instance).to receive(:read_uploader).with(:image).and_return('') is used
read_identifiers (https://github.com/carrierwaveuploader/carrierwave/blob/master/lib/carrierwave/mounter.rb#L27) returns empty array and thus uploaders (https://github.com/carrierwaveuploader/carrierwave/blob/master/lib/carrierwave/mounter.rb#L31) returns empty array.

When we use @instance.image= then cache method (https://github.com/carrierwaveuploader/carrierwave/blob/master/lib/carrierwave/mounter.rb#L39) is used which sets @uploaders and now @uploaders consist of one uploader without a file which makes whole that truble.

[thomasfedb]

Is the return value of blank? defined anywhere in documentation or comments?

[thomasfedb]

@bensie This appears to be a reasonable change with good justification provided by @Bonias, can it be merged?

[bensie]

Thanks @Bonias!