GoCardlessPro::InvalidApiUsageError 'One of your parameters was incorrectly typed' after Rails 6.0.2.1 (session.id)

GoCardlessPro::InvalidApiUsageError 'One of your parameters was incorrectly typed' after Rails 6.0.2.1 (session.id)

What's going on

After upgrading to Rails 6.0.2.1, creating a GoCardless redirect flow failed with GoCardlessPro::InvalidApiUsageError: One of your parameters was incorrectly typed. Rack changed session.id to return a Rack::Session::SessionId object instead of a String; the SDK serialized it as a JSON object and the API rejected it. A maintainer confirmed the diagnosis but declined to auto-cast parameters in the client library.

The verified fix

Pass a real string for sessiontoken - use `session.id&.publicid (the fix recommended by the Rails team) instead of bare session.id` when creating the redirect flow. GoCardless confirmed the parameter must be a string and won't cast it client-side, so the fix belongs in your app code. Source: https://github.com/gocardless/gocardless-pro-ruby/issues/67

How to use this

Take the question above and check if it matches what you're seeing. If it does, work through the verified fix step by step. Start with the cause described first, because that's what tells you the fix applies to your setup, then apply the changes in the order given. Verify by re-running whatever failed before, and expect the same behavior the thread author reported.

Someone asked: After upgrading to Rails 6.0.2.1, creating a GoCardless redirect flow failed with GoCardlessPro::InvalidApiUsageError: One of your parameters was incorrectly typed. Rack changed session.id to return a Rack::Session::SessionId object instead of a String; the SDK serialized it as a JSON object and the API rejected it. A maintainer confirmed the diagnosis but declined to auto-cast parameters in the client library. The verified answer: Pass a real string for sessiontoken - use `session.id&.publicid (the fix recommended by the Rails team) instead of bare session.id` when creating the redirect flow. GoCardless confirmed the parameter must be a string and won't cast it client-side, so the fix belongs in your app code. Source: https://github.com/gocardless/gocardless-pro-ruby/issues/67 Discussion and confirmation live at https://vectle.com/threads/thr_EXJAEt1mRmzmzdFCX55uvA