We were hiding the file input and styling the label as a button instead.
Since clicking on a label has the same effect as clicking on the input,
the input worked properly for mouse and touch screen users.
However, hiding the input makes it inaccessible for keyboard users,
since labels don't get keyboard focus, but inputs do.
So we must not hide the input but make it invisible instead. But we
still need to hide the input (alongside the label) after a file has been
attached.
We could add some extra JavaScript to hide the input when we hide the
label. Since the JavaScript is already quite complex and my first few
attempts at changing it failed, I've opted to assume that the input (and
its label) must be hidden whenever there's already a file name, and
implement that rule with CSS.
Note we're using the `:focus-within` pseudoclass to style a label when
focus is on the input. This rule (at the time of writing) is only
supported by 93.5% of the browsers. Keyboard users without a screen
reader and using the other 6.5% of the browsers will still be able to
focus on the field but might not notice the field has received focus.
Since the percentage of affected users will decrease over time and until
now 100% of keyboard users were completely unable to focus on these
fields, for now we think this is a good-enough solution.
We were already defining the links with data-remote and data-method, so
instead of manually doing an AJAX request we can rely on Rails to
perform the request and then handle the `ajax:complete` event.
This way screen reader users will hear the name of the file before
hearing about the link to destroy it. We were already displaying it this
way visually by having the file name on the left and the destroy link on
the right.
Thanks to this change we can also simplify the code which dynamically
changed the layout.
Since elements are created and destroyed, we don't have to do any kind
of "reset" before destroying or creating them. We would have to do so if
we were just hiding the elements in order to show them again later, but
that's not the case.
Using the same variable name makes the code more difficult to read.
We're also enabling the `no-param-reassing` rule since we accidentally
reassigned params in commit 824dd26d, and this rule will prevent us from
doing so in the future.
For now we're only adding rules related to spacing and double quotes,
following the same rules we use in Ruby, which are the same rules
CoffeeScript followed when compiling these files.
We're also using the recommended ESLint rules, which will warn us about
many JavaScript common pitfalls, the `strict` rule which enforces using
strict mode, and the `no-console` rule, which will prevent us from
shipping code meant for debugging.
Although it's arguably more common to use the JSON format to define
these rules, I've chosen YAML because it's the format we use in all our
linters.
These statements were automatically added by CoffeeScript.
I'm only removing the obvious cases; there might be more cases where the
`return` statement isn't necessary.
