Best way to set default for an optional local in a partial?

What’s the best way to set the default value of an optional local
variable in a partial template?

In the past I’ve used

<% foo = default_value unless (defined? foo) %>

But ActionView::Base says not
to use (defined? foo) and instead use (local_assigns.has_key? :foo) thus

<% foo = default_value unless (local_assigns.has_key? :foo) %>

Some have suggested

<% foo ||= default_value %>

which has the benefit of compact syntax, but will override passed values
of nil and false. Some have also suggested

<% foo = default_value if local_assigns[:foo].nil? %>

which will override the passed value nil.

Are there other pros and cons to consider here? Are any of these
strictly preferred over the others