Do not fetch attribute values for excluded models

[Gasparila]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Related Issue	N/A
Need Doc update	no

Describe your change

Upon upgrading from 1.20 => 1.22 we noticed errors due to changes around
handling excluded records. This PR implements a fix by only fetching
attribute names when determining if an index operation is necessary and
adds a test to ensure that our use case will not break. Example model

class Example < ActiveRecord::Base
  include AlgoliaSearch

  algoliasearch :unless => :nil_name do
    attribute :name_length do
      # will crash if name is nil
      name.length
    end
  end

  def nil_name
    name.nil?
  end
end

[Gasparila]

@julienbourdeau any thoughts on this?

[julienbourdeau]

@Gasparila I think it's a good improvement 👍

I don't see what caused the issue between 1.20 and 1.22 tho 🤔 did you track it down?

[Gasparila]

@julienbourdeau yes I did

af11c8f#diff-dfaec67e907148ea8211e17340f0f30cR149

Changed the get_attribute_names to get get_attributes(object).keys instead
of the previous behavior that would only look at the names. As a result, the values
are computed when we are fetching the names

[Gasparila]

Any update on this @julienbourdeau? We'd love to move back onto the main fork of the repo

[bkdir]

Curious if this is a consideration? Calculating values just to get names causing unexpected errors.

[bkdir]

line 164 would still resolve your attributes. should be changed as @serializer._attributes to get attribute names without actually calculating the values.