Patternlab should become a concrete class

[tburny]

I am using Pattern Lab Node v2.7.0 (dev) on Linux, with Node v4.6.2, using the Grunt Edition.

Currently, the Patternlab "class" is just an object ({})which is extended here and there. Here a "convention over configuration" pattern is applied: Properties of the PL object are added as required.

This approach has the following disadvantages:

• The overall set of propierties the PL object can have is not defined thoroughly
• It is difficult to provide some sensible defaults in unit tests. This causes lots of DRY code which could be replaced by something like Patternlab.createEmpty(additionalSettings)
• It became and becomes more and more a god-object required everywhere

To overcome these problems I propose

• to create a class with a predefined set of fields, similar to the Pattern class. This also would probably improve overall modularity of the application.
• Replace some dependencies on the PL class with what is really required for a given method (improves testability and modularity). The goal is to un-god the object a bit
• See if we can move some methods to the PL object.

The structure would be as follows:
PatternlabEngine has a Patternlab object with the fields engines, package, config, events, graph (#540), patterns, , subtypePatterns, data, listitems, patternSection, patternSectionSubType, header, footer, partials, data.link(for completeness). Also it has at least a method to load+check the configuration from a JSON file. Probably major parts ofpatternlab.js` could eventually be moved into there.
Additionally it might be wise to apply a strategy pattern to how patterns are compiles (compile all, incremental, whatever).

Opinions?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[bmuenzenmeyer]

@geoffp PING

[geoffp]

In progress!

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[bmuenzenmeyer]

This was done as part of https://github.com/pattern-lab/patternlab-node/releases/tag/v3.0.0-alpha.5