Show blocked brands in CBC dropdown, but block selection

[porter-stripe]

Summary

• Instead of just hiding disallowed card brands in the CBC dropdown, we should instead show them as disabled and prevent them from being selected. When the user attempts to scroll to a disallowed brand it is "rolled back" to the previous selection.

Update card flow

Simulator.Screen.Recording.-.iOS.18.-.2025-01-22.at.09.45.28.mp4

New card flow

Simulator.Screen.Recording.-.iOS.18.-.2025-01-23.at.09.25.00.mp4

Motivation

https://jira.corp.stripe.com/browse/MOBILESDK-3035

Testing

• New unit test
• Manual

Changelog

N/A (private beta for now)

[github-actions]

⚠️ Missing Translations
The following strings have been uploaded to Lokalise but are not yet translated.

(not accepted)

If it's okay for these strings to be unlocalized in master (e.g. this is for an unshipped feature), add the label ship without translations to acknowledge that there are missing translations. Otherwise, wait until translations are available in Lokalise and re-run this job.

New strings are localized on a weekly basis and are downloaded as part of the release process. For more details on how to localize a string, you can refer to this link.

[porter-stripe]

Added the "ship without translations" b/c:

1. This feature is in private beta
2. None of the merchants using this feature use CBC

By the time we GA this feature translations will have come in, we won't GA until they do.

[wooj-stripe]

Instead of fatal Error, we should be using stpAssert to avoid being noisy for integrators, but..taking a step back, is it really needed to have a fatal error/assert? Seems the function should just be something like:

var isUpdatableCardBrandCard: Bool {
    guard paymentMethod.type == .card {
        return false
    }
    let availableBrands ...
    etc...
    return...
}

[porter-stripe]

Yeah, I like this, good idea.

[wooj-stripe]

Seems like we should assert the number of items before directly accessing specific indexes.

[wooj-stripe]

Seems like we should add to the top of the fn:

        guard row < items.count else {
            stpAssertionFailure("...")
            return
        }

[wooj-stripe]

Would be good to keep a consistent nomenclature of disallowed instead of introducing isAllowed

[porter-stripe]

Yeah agree!

[wooj-stripe]

I'm having a tough time following this logic, so i tried to refactor it a bit.... Let me know what you think about breaking up this logic in the following way:

   ....
               cardBrandDropDown.update(items: DropdownFieldElement.items(...)
   ....
               // Prioritize merchant preference if we did not have brands prior to calling .possibleBrands, otherwise use default logic
               if !hadBrands, let indexToSelect = hasPreferredBrandIndex(fetchedCardBrands: fetchedCardBrands, disallowedCardBrands: disallowedCardBrands, cardBrandDropDown: cardBrandDropDown) {
                   cardBrandDropDown.select(index: indexToSelect, shouldAutoAdvance: false)
               } else if let indexToSelect = useDefaultSelectionLogic(disallowedCardBrands: disallowedCardBrands, cardBrandDropDown: cardBrandDropDown) {
                   cardBrandDropDown.select(index: indexToSelect, shouldAutoAdvance: false)
               }

Then we take the logic out of those ifstatements into two separate functions:

        // Select the first brand in the fetched brands that appears earliest in the merchants preferred networks
        func hasPreferredBrandIndex(fetchedCardBrands: Set<STPCardBrand>, disallowedCardBrands: Set<STPCardBrand>, cardBrandDropDown: DropdownFieldElement) -> Int? {
            guard let preferredNetworks = self.preferredNetworks,
                  let brandToSelect = preferredNetworks.first(where: { fetchedCardBrands.contains($0) && !disallowedCardBrands.contains($0) }),
                  let indexToSelect = cardBrandDropDown.items.firstIndex(where: { $0.rawData == STPCardBrandUtilities.apiValue(from: brandToSelect) }) else {
                      return nil
                  }
            return indexToSelect

        }

        // If we only fetched one card brand that is not disallowed, auto select it.
        // This case typically only occurs when card brand filtering is used with CBC and one of the fetched brands is filtered out.
        func useDefaultSelectionLogic(disallowedCardBrands: Set<STPCardBrand>, cardBrandDropDown: DropdownFieldElement) -> Int? {
            let validBrandSelections = cardBrandDropDown.items.filter { !$0.isPlaceholder && !$0.isDisabled }
            guard validBrandSelections.count == 1,
                  !disallowedCardBrands.isEmpty,
                  let firstItem = validBrandSelections.first,
                  let indexToSelect = cardBrandDropDown.items.firstIndex(where: { $0.rawData == firstItem.rawData }) else {
                return nil
            }
            return indexToSelect
        }

[porter-stripe]

Ah I like this better!