Abstract `ContextManager` usages behind `CoreDataStack`

[mokagio]

Part of #24165

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Problem I can't move AbstractPost and other Objective-C models in WordPressDataObj because they access ContextManager which is defined in the Swift WordPressData.

Solution Decouple from knowing about a specific type (ContextManager) and use a protocol instead (CoreDataStack). This came with a few compromises (see inline comments) but I think it got the job done relatively clean.

I tested this by running Jetpack on my iPhone and doing a smoke test checking the various tabs.

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An alternative solution if we run into more Swift leakages into Objective-C would be to backtrack and create a framework target where we can have mixed languages. I might set aside some time today to search for #import "WordPress-Swift.h" usages and see how much extra steps like this would be needed if we kept the packages setup.

[dangermattic]

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[mokagio]

@crazytonyli

Sorry if I missed the discussion, but any reason not moving ContextManager into WordPressData too?

ContextManager will eventually go into WordPressData, yes. (Current broken WIP PR that reveals all these issues https://github.com/wordpress-mobile/WordPress-iOS/pull/24166)

[crazytonyli]

I wonder whether moving ContextManager first would be easier for moving the managed objects. Like, this decoupling refactor would not be necessary if ContextManager is already in WordPressData.

[mokagio]

this decoupling refactor would not be necessary if ContextManager is already in WordPressData.

I think it would still be necessary if we have WordPressData the Swift package + WordPressDataObjC the Swift package with only Objective-C files. Because WordPressData depends on WordPressDataObjC, and therefore WordPressDataObjC cannot depend on WordPressData. But ContextManager is in WordPressData and the AbstractPost in WordPressDataObjc.

[mokagio]

@crazytonyli your question actually made me realize that some of the models are Objective-C and others are Swift. I'll need to quickly verify whether they can work sparse between the two packages, or if I should just call it quits on the package and use a framework instead :/

[kean]

Looks like it's obsolete now.