Add a global variable to disable search autocomplete

[kevindew]

The new search autocomplete is due to be rolled out across GOV.UK.

Autocomplete uses a denylist to stop certain terms from serving suggestions. The process to update the denylist is very manual and developer heavy.

If might be difficult to update the denylist over the holiday period. In that situation the decision might be taken to temporarily turn off autocomplete entirely.

A global environment variable has been added to each environment rather than individual environment variables for each affect app, as the search bar exists in the header on all pages on GOV.UK. This means that it needs to be accessed by the layout_super_navigation_header 1 which is pulled in by static for use in 6 other rendering apps.

We are using an env var to disable this feature rather than enable it so that by default developers using these apps do not need to set-up extra env vars to use the app as it runs in production, with an expectation that it is unlikely that this feature would be disabled for a prolonged period.

When disableSearchAutcomplete is set to true an env var of GOVUK_DISABLE_SEARCH_AUTOCOMPLETE will be set with a value of "1", when disableSearchAutocomplete is false then no env var is set. Apps that use this env var can do:

if ENV["GOVUK_DISABLE_SEARCH_AUTOCOMPLETE"]
  # render search without autocomplete
else
  # render something with autocomplete
end

It is expected that once the autocomplete feature is settled in GOV.UK there will no longer be a need to disable it and this code can be removed, ideally this will happen in Q4 2024-2025 while the Search team is completing the deployment of this feature.

[nimalank7]

Shouldn't this be true?

[kevindew]

It doesn't actually matter as we expect applications to check just for the presence of the env var. I went for "1" rather than "true" as I didn't want to create an impression that "false" would override it - as any env var value will be an indication of disabling.

[nimalank7]

LGTM!

[theseanything]

This will work - not sure it's the clearest way to state the logic.

Having an env var:
GOVUK_ENABLE_SEARCH_AUTOCOMPLETE
which can be set to true or false (the default being true).

Then in env-configmap.yaml:

GOVUK_ENABLE_SEARCH_AUTOCOMPLETE:  {{ .Values.govukEnableSearchAutocomplete | default "true" }}

If needed to be disabled, you just add the following into the environment's value file:

govukEnableSearchAutocomplete: "false"

Avoids double negatives and having to reason about what happens if the env var is missing entirely.

Realise this is a minor change that is likely to be removed - happy for it to go in as is. But considerations for future work that require setting a global env var.

[kevindew]

Thanks @theseanything we went down this route to avoid each of the numerous apps that use this needing to set-up the env var for local dev. Where the only way the suggestion you have would work for those is if they did a check of if ENV["GOVUK_ENABLE_SEARCH_AUTOCOMPLETE"] == "false" and that also feels strange to have a variable named "enable" but could only be used to disable.

I know not the most clean, but I don't think there is a purely clean route with boolean env vars.