docs(adr): add Developing and Publishing ClientSide Behaviours

[keithamus]

This records some architectural decisions on how we will add client side (JS) behaviours to PVC.

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🔍 Inspect: https://vercel.com/primer/view-components/GZnYiw8XR5RoqcsPkT9unHwnh8CK
✅ Preview: https://view-component-git-docs-adr-add-developing-and-publishin-d4892d.vercel.app

[joelhawksley]

👏🏻

[joelhawksley]

👋🏻 one other thought here: have we considered if we might want to provide some sort of encapsulation of the Javascript we write for ViewComponents? I could see us coupling the two together in similar fashion to our explorations of CSS modules, generating a selector specifically for a component and using it in the JS.

[keithamus]

Our current architecture is leveraging Web Components, which are encapsulated by tag name. Attempting to define an already defined web component causes an exception on the front-end.

Web Components are encapsulated in that they are only activated for/on the pre-defined tags. In other words behaviour is not executed globally, only when an element enters the dom.

Not in the scope of this ADR but something I want to explore further is adding a suite of meta-tests which assert that the JS follows good conventions, such as:

• The naming of JS files matches the naming of components.
• The JS avoids global behaviours where applicable.
• Any component with a JS file must have an integration test.

[joelhawksley]

Attempting to define an already defined web component causes an exception on the front-end.

This is the aspect I'm curious about. Can we provide an architecture where this exception is raised at compile time or as part of a test suite?

(This isn't a blocker at all)

[keithamus]

This is already implicitly part of our test suite as we include the compiled bundle in the system tests!

[keithamus]

I think this is ready to go. This mostly now reflects reality, as we've implemented most of what this ADR documents.