Remove deprecated govuk-button--disabled class

[querkmachine]

Removes the .govuk-button--disabled class that was deprecated in 4.6.0. Closes #2681.

Changes

• Removes the .govuk-button--disabled selector and the deprecation comment from the stylesheet.
• Removes the disabled link example from the review app.
• Removes the test associated with the disabled link example.
• Updates the Nunjucks macro to no longer add the .govuk-button--disabled class to disabled buttons.
• Updates the Nunjucks macro documentation to indicate that the disabled parameter has no affect on a elements.
• Updates tests to no longer check for the existence of the .govuk-button--disabled class.

Thoughts

We also have a .govuk-button[disabled="disabled"] selector defined in there. I'm not sure why this exists alongside .govuk-button[disabled], as they have the same specificity and disabled is a boolean attribute (the presence of a value is meaningless).

.govuk-button[disabled] alone would seem to suffice. Should we also remove .govuk-button[disabled="disabled"]? I don't think doing so would require a deprecation or breaking change.

[querkmachine]

The changelog might be a bit awkward as there's already a section regarding changes to disabled buttons. I've tried to merge these changes into it rather than having a separate, similarly titled section.

[owenatgov]

Looks good to me 💪🏻

I'm unsure if we should also remove disabled="disabled". Nothing struck me as a reason it was there in the commit history that I was able to uncover. My guess is this is a failsafe for incorrect implementations? I'm leaning towards not deleting it but it also feels like that's just kicking the can down the road. Maybe we should just get rid of it 👀

[querkmachine]

My guess is this is a failsafe for incorrect implementations?

Unless I'm having a late afternoon brainfart (not unheard of!) I'm not aware of any implementation that .govuk-button[disabled="disabled"] would match and that .govuk-button[disabled] wouldn't also match.

Even if teams have added their own styles for either selector, the value-d option has no greater specificity than the value-less one, and a team's own styles will trump both of them on the cascade alone anyway.

I feel pretty safe taking it out, I'm pretty confident it can't break anything.

[36degrees]

I agree with your conclusion – anything that's covered by button[disabled="disabled"] would already be covered by button[disabled]. So I think we can safely get rid of it.

I'm not 100% sure about merging the two entries under a single changelog entry – I'm mainly wondering if the second one might get missed.

I do think we should refer back to it's deprecation, like we did for the previous major release. If users have been acting on our deprecations they shouldn't have to do anything – adding this would help them make that connection.