Multiple inheritence does not work correctly with relative operators

[colinjneville]

When a layout makes a relative adjustment to a key that does not appear in the last layout specified in extends, the value for that key is left as the string value including the operator (e.g. '+= 100').
For example, the example in the documentation for multiple inheritence will fail because x is a string:

socrates:
  x: 100
plato:
  y: 200
aristotle:
  extends:
    - socrates
    - plato
  x: += 50    # evaluates to 250 from plato

require 'squib'

Squib::Deck.new(cards: 1, layout: 'test.yml') do
  circle radius: 50, layout: :aristotle
  
  save_png prefix: 'test_'
end

lib/ruby/2.4.0/forwardable.rb:229:in `arc': no implicit conversion to float from string (TypeError)

I'm new to Ruby, so I may be reading something wrong, but it looks like recurse_extends merges the current layout with each parent separately (so aristotle/socrates['x'] is 150, aristotle/plato['x'] is '+= 50'), then those are all merged with the later parents taking priority when multiple values exist for the same key. Since aristotle/plato['x'] technically has a value, it overwrites the expected value, so aristotle['x'] == '+= 50'.

[andymeneely]

Yeah you're right - I remember fixing this somewhere back along the way. Wonder what happened.

You can also see what the layout computes to with a puts layout in there. In this case it comes out to

{"socrates"=>{"x"=>100}, "plato"=>{"y"=>200}, "aristotle"=>{"extends"=>["socrates", "plato"], "x"=>"+= 50", "y"=>200}}

Good catch. Looking into it.

[andymeneely]

Turns out I never tested this case. I think I've handled it. The docs were also wrong, so I fixed that too. The new docs will be correct once I put out the new release. Expect this fix in v0.14.2