Be less dependent on axios

[simplesmiler]

Motivation:

1. Axios does not support response streaming in browser, only in Node (there is intent, but no visible progress so far.). A readable "stream" can be acquired from Blob response, but the whole response body is buffered in memory anyways. Fetch, on the other had, supports streaming, although not in every browser.
2. Typed request builder can also be useful to developers who do not use Axios.

TL;DR

Current problems are:

1. We can not be independent of axios, because we need AxiosResponse generic.
2. Axios can not be peer dependency because TypeScript does not work well with peer dependencies. Not a problem anymore, was solved by also having it as dev dependency.

Details

To be independent of axios, we have to be able to arbitrarily wrap response types (e.g. Pet into AxiosResponse<Pet>).

But TypeScript does not support:

1. First class generics, e.g. generic as parameter for another generic.

   type Wrap<T> = { data: T };
   const taxios = new Taxios<Api, Wrap>(agent); // error: Wrap is not a type

2. ReturnType of generic function.

   type Wrap<T> = { data: T };
   type Wrapper = <T>() => Wrap<T>;
   type WrappedNumber = ReturnType<Wrapper<number>>; // error: Wrapper is not a generic

So far I could not find a way around that.

[simplesmiler]

Maybe this still possible with classes, because classes can have generic methods and can themselves be generic parameters.

But maybe we don't want per-agent response type at all, but always want native Response type branded with T?

[crutch12]

But maybe we don't want per-agent response type at all, but always want native Response type branded with T?

Native Response is too uncomfortable to work with. I think this is the reason why people use axios.

If you want to reject axios, I think we should create another npm module for that

[simplesmiler]

TLDR: I think axios is slowly becoming a "jQuery".

I think people use axios mostly because:

• XMLHttpRequest is awful to work with. Fetch feels much better in comparison (but not perfect), and axios feels even better (but at a cost of not supporting web streaming).
• Axios has interceptors for "global" behaviors, like logging, authentication and retry.

Native Response is too uncomfortable to work with.

I would like to argue that it's not really. Response and AxiosResponse have mostly the same interface, with only notable exceptions being:

• AxiosResponse has config: AxiosConfig, which is mostly used in interceptors.
• Response is returned before all data has arrived, so it has to be { json(): Promise<T> } instead of { data: T }. But I personally don't see much difference between taxios.get('/users').then(r => r.data) and taxios.get('/users').then(r => r.json()).

[simplesmiler]

Judging by axios/axios#4209, there is intent in axios to support web streams.