Add a ModuleManagerInterface for determining if a module is enabled

[navarr]

This is a useful addition for feature detection and enablement for third party modules (such as "activate this functionality if such and such GiftCard extension exists"

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[orlangur]

public function isEnabled($moduleName)
    {
        return $this->moduleList->has($moduleName);
    }

This is the only method of mentioned class. What is the purpose of proposed interface?

[navarr]

Purpose is to add an easy ability to determine if a module is enabled to the API. Currently neither the ModuleManager nor the ModuleListInterface are @api annotated

@orlangur

[orlangur]

Interface is only useful when implementation may be potentially switched. Why not mark class method with @api instead?

[navarr]

I can do that. I defaulted to an interface b/c I figured it'd be what'd be desired - after all, just b/c I can't think of an alternative implementation doesn't mean one can't exist!

Should I PR the addition on the model itself? Doing so would add a couple non-api deprecated methods to the API though

[orlangur]

I was thinking about marking only one method as @api.

Let me check in Slack whether there was some reasoning behind not marking this class as @api and whether we should mark class or method.

[orlangur]

Raised a question in Slack

Is there any reason of not marking https://github.com/magento/magento2/blob/2.2-develop/lib/internal/Magento/Framework/Module/Manager.php as @api?

[navarr]

@orlangur I'm guessing you never got any feedback in Slack?

[orlangur]

@navarr yeah, but now we have a better process.

[orlangur]

@antonkril @buskamuza please take a look on this interface suggestion. Of course it should be done against 2.3-develop but first it would be nice to understand whether such feature detection is an acceptable approach.

[antonkril]

Explicit isModuleEnabled checks are usually a sign of bad modularity.

But yes, such interface with @api annotation makes sense.

[antonkril]

Makes sense

[navarr]

I'm closing this PR to make a new one against 2.3