We have quite a lot of `Error reading file` errors when uploading files.
These errors are generated by ActiveStorage `file_checksum.js` component
but it eats the actual reason of errors.
(See https://github.com/rails/rails/blob/5-2-stable/activestorage/app/javascript/activestorage/file_checksum.js#L38)
We can't really override the class to generate better errors, as they
are deeply nested in ActiveStorage class hierarchy, and not exported to
external code.
Instead, we hook into the FileReader event handler, to insert a logger
when this error occur. The original event handler will also still be
called as usual.
This is intended to be temporary. The debug code will be removed once
we get a better idea of what is going on.
A DirectUpload may fail for several reasons, and return many types of
errors (string, xhr response, Error objects, etc).
For convenience, wrap all these errors in a FileUploadError object.
- It makes easier for clients of the Uploader class to handle errors;
- It allows to propagate the error code and failure responsability.
When the authenticity token is invalid, the creation of the blob before
the direct upload returns a 422.
In that case, the token will never become valid again, and it is useless
to try again. Don’t show the "Retry" button in this case.
NB: of course the real fix is to understand why the authenticity token
is so often invalid – but this will be for later.
When navigating away from the page, the field receives the 'focusout'
event – but stops to be present in the DOM.
Thus we need to check that the DOM element is actually present.
When a file is being uploaded asynchronosely, hidden input fields
are created by DirectUpload to contain the result of the upload.
However, before the upload finishes, the value of these inputs is not
meaningful. Moreover, it makes the ActiveRecord signature invalid – thus
preventing drafts from being saved.
Exclude these fields from the auto-save.
Older browsers implemented a different default value for `window.fetch`
credentials: it was omitted unless explicitely set.
So we force the value for these older browsers:
- Firefox 39-60
- Chrome 42-67
- Safari 10.1-11.1.2
See https://github.com/github/fetch#sending-cookies
