App Switch in New Tab

[naderchehab]

Description

Add support for new-tab based app switch flows to preserve merchant client-side state during PayPal checkout.

Problem

Today, when appSwitchWhenAvailable: true is set and the PayPal app is not installed, the SDK performs a full-page redirect to web checkout. This clears the merchant page's client-side state, which is problematic for merchants who rely on that state.

Solution

Introduce a new preferences object that allows merchants to configure app switch behavior:

  paypal.Buttons({
    preferences: {
      appSwitchWhenAvailable: true,
      launchAppSwitchIn: 'newTab'  // or 'sameTab'
    },
    createOrder: () => fetch('/api/orders').then(r => r.text()),
    onApprove: ({ orderID, isAppSwitchManualReturn }) => { /* ... */ }
  }).render('#paypal-buttons');

Behavior

• launchAppSwitchIn: 'newTab': Opens a loader in a new tab, deep-links to the PayPal app from there. If the app is not installed, web checkout renders in the new tab, preserving the merchant page state.
• launchAppSwitchIn: 'sameTab': Uses full-page redirect (existing/legacy behavior).

Why are we making these changes? Include references to any related Jira tasks or GitHub Issues

Reproduction Steps (if applicable)

Screenshots (if applicable)

Dependent Changes (if applicable)

Groups who should review (if applicable)

❤️ Thank you!

[binoybt]

This opens up possibility of errors.

[naderchehab]

Updated