GitLab utilities

We developed a number of utilities to ease development.

MergeHash

• Deep merges an array of hashes:

  Gitlab::Utils::MergeHash.merge(
    [{ hello: ["world"] },
     { hello: "Everyone" },
     { hello: { greetings: ['Bonjour', 'Hello', 'Hallo', 'Dzien dobry'] } },
      "Goodbye", "Hallo"]
  )

  Gives:

  [
    {
      hello:
        [
          "world",
          "Everyone",
          { greetings: ['Bonjour', 'Hello', 'Hallo', 'Dzien dobry'] }
        ]
    },
    "Goodbye"
  ]

• Extracts all keys and values from a hash into an array:

  Gitlab::Utils::MergeHash.crush(
    { hello: "world", this: { crushes: ["an entire", "hash"] } }
  )

  Gives:

  [:hello, "world", :this, :crushes, "an entire", "hash"]

StrongMemoize

• Memoize the value even if it is nil or false.

  We often do @value ||= compute, however this doesn't work well if compute might eventually give nil and we don't want to compute again. Instead we could use defined? to check if the value is set or not. However it's tedious to write such pattern, and StrongMemoize would help us use such pattern.

  Instead of writing patterns like this:

  class Find
    def result
      return @result if defined?(@result)
  
      @result = search
    end
  end

  We could write it like:

  class Find
    include Gitlab::Utils::StrongMemoize
  
    def result
      strong_memoize(:result) do
        search
      end
    end
  end

• Clear memoization

  class Find
    include Gitlab::Utils::StrongMemoize
  end
  
  Find.new.clear_memoization(:result)