Adds cached_client method in BaseConnection

[dmccown]

Adds a helper method in base connection so you no longer have to
duplicate caching logic in any plugins you may create. Example:

def demo_client
  cache_client(:api_call, :demo_connection) do
    DemoClient.new(options)
  end
end

This will automatically check if the cache is enabled and return the the
cached object if it exists. If it doesn't exist then the cache will be
hydrated.

Signed-off-by: David McCown dmccown@chef.io

[TrevorBramble]

@cache.dig(type, key) ||= yield?

[dmccown]

I wasn't sure if you could do assignment when using dig.

[dmccown]

That doesn't work. You aren't allowed to do assignment from the return of dig.

train/lib/train/plugins/base_connection.rb:56: syntax error, unexpected tOP_ASGN,
expecting keyword_end (SyntaxError)
      @cache.dig(type, key) ||= yield

[TrevorBramble]

Yeah, you're right. I wasn't thinking about the assignment. That's a shame--it should work that way!

[TrevorBramble]

It wouldn't be useful in the other tests, because they don't look anything like real world code, but this one made me wonder if we could just return self from enable_cache() and disable_cache(). I quick search shows that the implicit return of a boolean is never treated as significant.

def enable_cache(type)
  fail Train::UnknownCacheType, "#{type} is not a valid cache type" unless @cache_enabled.keys.include?(type.to_sym)

  @cache_enabled[type.to_sym] = true

  self
end

it 'returns a new connection when cache enabled and not hydrated' do
  conn = DemoConnection.new.enable_cache(:api_call)

  client1 = conn.demo_client
  client1.must_be_instance_of DemoConnection::DemoClient
end

# or even...

it 'returns a new connection when cache enabled and not hydrated' do
  client1 = DemoConnection.new.enable_cache(:api_call).demo_client

  client1.must_be_instance_of DemoConnection::DemoClient
end

[jquick]

Thanks @dmccown