undefined method `replace_engine' for nil:NilClass when using custom cache engine

[BastianHofmann]

I'm getting a undefined method 'replace_engine' for nil:NilClass error when using a custom cache engine.

  config.cache_engine = Rabl::CustomCacheEngine.new

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.
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module Rabl
  class CustomCacheEngine

    def fetch(key, cache_options, &block)
      if defined?(Rails)
        Rails.cache.fetch(prefix_key(key), cache_options, &block)
      else
        yield
      end
    end

    def write(key, value, options = {})
      if defined?(Rails)
        Rails.cache.write(prefix_key(key), value, options)
      end
    end

    def read_multi(*keys)
      options = keys.extract_options!
      keys.map! { |key| prefix_key(key) }
      if defined?(Rails)
        Rails.cache.read_multi(*keys, options)
      else
        keys.inject({}) { |hash, key| hash[key] = nil; hash }
      end
    end

    protected

    def prefix_key(key)
      "#{Apartment::Tenant.current_tenant}/#{key}"
    end
  end
end

Stack trace:

rabl (0.11.6) lib/rabl/multi_builder.rb:97:in `block in replace_engines_with_cache_results'
rabl (0.11.6) lib/rabl/multi_builder.rb:94:in `each'
rabl (0.11.6) lib/rabl/multi_builder.rb:94:in `replace_engines_with_cache_results'
rabl (0.11.6) lib/rabl/multi_builder.rb:24:in `to_a'
rabl (0.11.6) lib/rabl/engine.rb:88:in `to_hash'
rabl (0.11.6) lib/rabl/engine.rb:101:in `to_dumpable'
rabl (0.11.6) lib/rabl/engine.rb:110:in `to_json'
rabl (0.11.6) lib/rabl/engine.rb:48:in `block in render'
activesupport (4.1.9) lib/active_support/cache.rb:296:in `block in fetch'
activesupport (4.1.9) lib/active_support/cache.rb:587:in `block in save_block_result_to_cache'
activesupport (4.1.9) lib/active_support/cache.rb:548:in `instrument'
activesupport (4.1.9) lib/active_support/cache.rb:586:in `save_block_result_to_cache'
activesupport (4.1.9) lib/active_support/cache.rb:296:in `fetch'
app/features/rabl/custom_cache_engine.rb:6:in `fetch'

[BastianHofmann]

For now I was able to monkey patch with:

  class MultiBuilder
    def replace_engines_with_cache_results
      @cache_results.each do |key, value|
        engine = @cache_key_to_engine[key]
        builder = @engine_to_builder[engine]
        builder.replace_engine(engine, value) if value && builder
      end
    end
  end

[MilanJ88]

Had the same issue, the monkeypatch solved it.