How to add aria-label attribute to a link in a view?

It's the dash on the label creating the problem. Try this instead:

<%= link_to t('nav.projects'),
            projects_path, class: is_active('projects'),
            'aria-label' => get_aria_label_current_page('home') %>

Update

In ruby 2.2 now you could do:

'aria-label': get_aria_label_current_page('home')

As of at least Rails 5.2 this works too:

<%= link_to t('nav.projects'),
            projects_path,
            class: is_active('projects'),
            aria: { label: get_aria_label_current_page('home') } %>

This is similar to how data-* attributes work, which is nice since you can add more than one and have them grouped.

This may work on earlier versions but I have not checked.