`${param}` variables are not resolved in constructs

[getlift]

`${param}` variables are not resolved in constructs

[mnapoli]

Hey @pedrodim, thanks for the report. This is indeed something that we need to clarify: because of the way Serverless loads all the plugins and resolves variables, this leads to some circular dependencies with constructs.

Using the initialize hook indeed messes up a few things.

I'll investigate right away if we can solve this specifically. If we can't, I'll document the limitation.

[pedrodim]

Thank you so much!

An idea could be have each construct expose a initialize hook (like they do currently with afterDeploy) so that they could instantiate any dependency or internal config which could use variables there instead on the constructor.

From what I've seem on serverless/serverless#3911 other plugins have solved this by moving any logic that uses variables to a hook, maybe it is something that cannot be possible for all actual constructs but for some this could be a workaround.

[mnapoli]

constructs:
    jobs:
        type: queue
        worker:
            handler: worker.handler
        maxRetries: ${param:maxRetries}
        batchSize: ${env:BATCH_SIZE}

In the example above, ${env:BATCH_SIZE} will be resolved correctly, but not ${param:maxRetries}.

The reason (I suspect) is related to the order in which variables are resolved. I'm still digging into it, I may have a lead.

[mnapoli]

I am working on #31 that should fix this issue.