🔗 Linked issue

Closes

• Allow having interceptos from both defaults and per request #319
• Ability to return a new response from onResponseError #160

❓ 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

Currently interceptors specified in $fetch() override the interceptors in $fetch.create.
This PR implements:

1. The interceptor "merge strategy" options that allow you to have both default and per-request interceptors. You can add interceptor as an object with handler and strategy fields when creating new client using $fetch.create. Available strategies:

• 'overwrite' - current behaviour
• 'after' - interceptor in $fetch will be called after the interceptor in $fetch.create
• 'before' - interceptor in $fetch will be called before the interceptor in $fetch.create
• 'manual' - interceptor in $fetch.create decides how/when/if call interceptor from $fetch

In all cases interceptor has second parameter which can be:

• response data
• data return by the previous interceptor

Names are subject to change 👀

2. It is now allowed to return new response data from the onResponse, onResponseError interceptors.
   If the function doesn't return anything or returns undefined - the response data will not be overwritten.

Example:

const myFetch = $fetch.create({
  onResponse: {
    strategy: "after",
    handler(ctx, data) {
      return 'global: ' + data
    },
  }
})

const r = await myFetch<string>("http://httpstat.us/200", {
  onResponse(ctx, data) {
    return 'local -> ' + data
  }
})

console.log(r) // will print "local -> global: 200 OK"

The open question is how to type the "data" parameter, currently it has type any.

We can also introduce the defaultStrategy option.

📝 Checklist

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