Make the Prototype Kit work with GOV.UK Frontend 6.0.0

[owenatgov]

Brief

Ensure that the Prototype Kit works against GOV.UK Frontend 6.0.0.

Frontend 6.0 includes a number of breaking changes:

• a new colour system, including the removal of 'verbose' colour keys eg: 'light-grey' and the removal of the govuk-tint and govuk-shade functions
• a restructuring of the applied colours system
• dropping support for libsass and ruby sass and pinning the minimum supported version of dart sass to 1.79
• many removed deprecated things

We need to make sure that the prototype kit and users of the prototype kit are able to use the kit with Frontend 6.0 so that they are able to continue prototyping in line with changes to Frontend.

Notes

What's been done so far

The new colour system has been tested against the kit in alphagov/govuk-frontend#5786

The findings were that there's only one place to update: the pagination component. However, if we make the update to these colours, it means that users on Frontend < 6.0 now won't be able to compile their sass, meaning that this would be a breaking change.

If we're going to release a breaking change anyway, a further thought is that we could remove the pagination component along with other instances of 'legacy' patterns and components within the kit. There's a hypothesis that this would also mean that users could upgrade their kits but still use Frontend 5.x if needed, but this needs testing.

Questions still to answer

• Should we release a breaking change of the prototype kit?
• Does the kit need further work with other changes coming in 6.0? eg: other removals, the applied colours system etc
• Can users still use Frontend 5.x if we remove old sass? answer: YES
• What updates do we need to make to the Kit docs if we make these changes?

Additional comments

We may also want to try to address the use of serviceName in the header component. This is being worked on at time of writing via #2466

Questions which need to be answered will be discussed in the next dev catch up.

[joelanman]

There's a hypothesis that this would also mean that users could upgrade their kits but still use Frontend 5.x if needed

This would be great if at all possible

[owenatgov]

I did some rough testing removing pagination, legacy patterns and task list and running the kit locally. When the local kit is set to 6.0.0-beta.0 with those patterns removed and I run start:dev, the temp kit that's started for testing is on govuk-frontend 5.13 and runs no problems!

I need to figure out the best way to test a local instance of the kit in a way that lets me both control the govuk-frontend version directly via npm and do the same with the kit, which would allow me to test when both the kit and the local instance are set to 6.0. However I'm feeling hopeful.

[owenatgov]

Update: I've figured it out.

1. create a local directory and cd into it
2. run npx ../govuk-prototype-kit create --version local

This has also enabled me to prove my hypothesis that users on 5.x and 6.x can both use a hypothetical v14 of the kit 🎉

[owenatgov]

A few considerations that have come up so far in exploratory work for this alongside what I've noted above.

Effort to update the prototype kit + related repos to v6

From some local testing and running the acceptance tests in #2468, it looks like the principal thing to consider is the step by step prototype kit plugin. Thankfully updating this is trivial. I've removed $legacy from the step by step and have a PR open to update the colour keys that need updating.

What I've yet to do is:

• check the kit, common templates or the step by step against our many deprecation removals from this cycle, which will hopefully be easier once we have our next pre-release out
• check the kit docs for what needs updating

I also don't know how other changes in v6 such as the move to custom properties is going to impact the kit which we should check.

Communicating these changes

We'll obviously need comms for this. In theory this is a much lower-key release compared to v13. Previous breaking releases of the kit would just include slack comms and a more verbose than usual changelog entry.

One thing of note here is legacy patterns. These are from before v13 when all the templates were in the kit itself. The legacy patterns feature was a way to let folks transition to common templates slowly. However it wasn't ever properly communicated that these were now legacy.

If we decide to remove legacy patterns we should consider this in our comms strategy. Similarly, we could adjust the release to only include pagination, maybe task list, and park legacy patterns for another day. Possibly we could deprecate legacy patterns now somehow.