[LazyBlock] Allows using complex expressions with configuration#1931
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…-grape#1931) * Introduces the concept of a LazyBlock which gets excecuted on mount * Fixes LazyBlock within a namespace * Adds more specs so that given can also be used for conditional lazy blocks * Documents expressions * Adds a changelog * Update README.md
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This PR is motivated by a bug I've introduced on our system.
The problem, when you are trying to waterfall a configuration, is that
LazyValuedoesn't play nicely inside an expression so this codeIs evaluated when the class is load as: configuration[:attribute] => LazyValue || 'default_value' => LazyValue
Which means that even when you mount the API with
attribute: nilthe value will equalnilrather than'default_value'as a developer might expect.To mitigate this, I've introduced a lazy block, so you are able to put that expression within a
mountedblock which will only be evaluated when the API is mounted, and furthermore, will prevent methods using the response of the expression to running before the API is mounted