shovelling to nowhere.rb

@data = {}

def default_src(*args)
  if args.first
    @data[:default_src] = args.map(&:to_s)
  else
    @data.delete(:default_src)
  end
end

# Initial state is blank
@data # => {}

# Setting a value for it, updates data as expected
default_src "none" # => ["none"]
@data # => {:default_src=>["none"]}

# Calling with no args wipes it out
default_src # => ["none"]
@data # => {}

# Given a value, trying to append in doesn't behave as expected
@data[:default_src] = ["none"]

default_src << "more" # => ["none", "more"]
@data # => {}

=begin

The really interesting bit is the default_src << "more" line.

This breaks down as

    (default_src) ([result] << "more")

`default_src` follows the else branch inside the method, which removes the key/value from the @data hash
then returns that object that was just removed `["none"]`

We then execute `["none"] << "more"` which happily produces `["none", "more"]` **but that's not stored anywhere**

Then looking up the content of `@data` shows the source of truth knows nothing about our array shovelling.

=end