feat: retry callback

[enkot]

🔗 Linked issue

resolves #358
resolves #355 (updated)

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This PR adds support for a callback for retry option, which is a function that takes a fetch context object and count of retries and returns a boolean (true if the request needs to be retried):

await $fetch('/cart', {
  retry: (ctx, count) => {
    return count <= 3 && ctx.error?.code === '007'
  }
})

It runs onError and after a response, so the developer can decide when the request needs to be retried.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[enkot]

@pi0 Could you please check? I think it's a really flexible solution.

[cernymatej]

I love this idea. Probably link my issue as well as this should cover that use case too: #355

[AryanShrivastava18]

@enkot By when can we expect this change to be the part of the release? Is there anything I can give a support for to push it to release?

[lacherogwu]

retryCount will be essential 🙏

[fredericDelaporte]

@gustavopch,

My 2 cents: shouldRetry seems to better describe what this does.

The PR does not add a new option. It alters an existing one which currently can only be number | false, for it to also accept a callback returning a boolean or promise of a boolean. See here if you are not aware of that existing option. (Maybe @lacherogwu too.)

@enkot, thanks for the PR, I too would need this feature. I hope it can get merged. It would likely help if you could resolve the conflicts it has with current code.

But maybe it will not entirely cover my use case: an API that may return 401 on Bearer authentication with an access token, and having an endpoint taking refresh tokens for renewing the authentication. With your callback, I could attempt to renew the token
and retry the query if the refresh succeeded, assuming there is a way to alter the headers to be sent for the retry, in order to use the new bearer token.