Android Tap-to-Pay does not populate foreign_transaction_id consistently with card reader

[jacopofranza]

Problem

On Android Tap-to-Pay, the plugin does not propagate the Flutter foreignTransactionId in a way that makes the transaction retrievable through the Transactions API using foreign_transaction_id.

This makes Android Tap-to-Pay inconsistent with the card reader flow.

Current behavior

When using card reader checkout, foreignTransactionId is propagated correctly and the transaction can be retrieved via foreign_transaction_id.

When using Android Tap-to-Pay, the same external id is currently mapped only to CheckoutData.clientUniqueTransactionId, while CheckoutData.affiliateData is left null.

As a result, the transaction is not consistently retrievable through:

transactions.get(merchantCode, { foreign_transaction_id: externalId })

Expected behavior

Android Tap-to-Pay should behave consistently with card reader checkout:

• the external id passed from Flutter as foreignTransactionId should populate SumUp's foreign_transaction_id
• integrators should be able to query both card reader and Android Tap-to-Pay transactions using the same backend lookup strategy

Root cause

In the Android Tap-to-Pay flow, the plugin currently builds CheckoutData with:

• clientUniqueTransactionId set from payment["foreignTransactionId"]
• affiliateData = null

However, in the TTP SDK, foreignTransactionId belongs to AffiliateModel, which is attached through CheckoutData.affiliateData.

Proposed fix

Pass the plugin affiliateKey into the Android Tap-to-Pay checkout runner and set:

• clientUniqueTransactionId
• AffiliateModel(affiliateKey, foreignTransactionId, null)

This keeps the public Flutter API unchanged and fixes Android TTP reconciliation for foreign_transaction_id.

Related PR

Proposed fix: #68