Add support for File attachment

[djcp]

Implemented during a pair session with @seanpdoyle, this adds the ability for Formulaic to attach files to a form when given a File object.

[calebhearth]

Looks great.

[calebhearth]

Does this work in a js environment? I feel like there might be issues with that.

[seanpdoyle]

@calebthompson no, we didn't test in a js: true feature

We did however, out of curiosity, do some manual testing in chrome. According to jQuery, the contents of $("#user_avatar").val() is a filename string.

Having said that, @djcp and I noticed that during file-attachment, Chrome does some sandboxing magic. It translates the path of an attached file to something along the lines of C:\faked\<filename>, which could have some interesting side effects in capybara-webkit.

It could possibly cause the current version of tests to fail, since file.path could be translated to a path using the sandboxed file system.

@djcp any thoughts?

[djcp]

We bound this to the File class, thinking we'd be less likely to run into sync issues related to threads. You'd be more encouraged to use a persisted file as your fixture rather than a tempfile or IO handle that would probably work in the same thread but not across a JS browser thread. Pretty sure this will work OK as designed, but there's probably some additional checks we could implement to, say, ensure it's reading a file that's been persisted to storage.

Do you have a demo project of some sort that exercises the formulaic gem, similar to http://github.com/thoughtbot/paperclip_demo ?

[calebhearth]

I'm happy with this. Merge at will.

[seanpdoyle]

👍