Bump markdown-rails from 2.1.0 to 2.2.0

[dependabot]

Bumps markdown-rails from 2.1.0 to 2.2.0.

Commits

• 54444c5 Bump version
• e49576b Set a default view context
• 1181cdc Use template handler
• 9114355 Put attr_writer :view_context back
• 1e25b61 Initialize with options
• 154c018 Delegate helpers
• d67af04 Change from instance to class for renderers
• d7ac839 Use Rails helpers for views instead of delegation
• 94a5a08 Pass view_context to markdown rails renderer
• 2e3e953 Add Github CI workflow
• Additional commits viewable in compare view

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[lfdebrux]

@dependabot recreate

[github-actions]

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[lfdebrux]

Our usage of this gem is so basic, that these test failures feel like a bug in the gem. Note that https://pr-940.www.review.forms.service.gov.uk/features is also giving a 500 error. There aren't any open issues that are related though, so we might need to put together a bug report ourselves.

Oh I see what's happened, the way ApplicationMarkdown works in the install template has changed in sitepress/markdown-rails@94a5a08. We just need to change our ApplicationMarkdown class to match. Would have been nice to have some release notes about that... This is because our ApplicationMarkdown has diverged somewhat. Let's see if we can bring it closer to the original...

[lfdebrux]

So what's happening here in detail:

• the markdown-rails gem creates a subclass of Redcarpet::Render::HTML to add its functionality, in MarkdownRails::Renderer::Rails, and expects us to subclass that in our own ApplicationMarkdown
• however, the govuk-markdown also creates a subclass of Redcarpet::Render::HTML in GovukMarkdown::Renderer to make its changes work
• Ruby doesn't have multiple inheritance for classes, so we when we write ApplicationMarkdown we have to pick either MarkdownRails::Renderer::Rails or GovukMarkdown::Renderer as the superclass, and then find a way to incorporate the changes needed from the other class
• currently we're inheriting from GovukMarkdown::Renderer and trying to make the expected interface for markdown-rails work by basically copying and pasting

However that is brittle, as seen with this version bump; the interface has changed (which is fair, this isn't the documented way of using the library), so to make our code work again we need to copy the changes from markdown-rails. Which is annoying and work we'd rather not be doing, we might as well just vendor the code.

Making the two gems work together would be easier if one or both exposed mixins so that we could create a class that inherits methods from both, but currently neither gem does.

[lfdebrux]

I've raised a PR against govuk-markdown suggesting adding a mixin module that we can use to simplify our usage with markdown-rails:

DFE-Digital/govuk-markdown#42