FIX: defined headers should be honored *over* injected headers

[kwhitley]

Expected Behavior

• If I set a content-type header, I should expect it to be honored, no matter what
• If I set a body (manually) in the options, I should expect it to be honored, no matter what

Actual Behavior

• If I set a content-type header, application/json will be sent anyway
• If I set a body (manually) in the options, the payload is sent instead

Use Case

I am attempting to send blob data through a fetcher instance. I can do this with native fetch, but not itty-fetcher:

const blob = new Blob(["This is some important text"], { type: "text/plain" });

fetch('https://ity.sh/create', { method: 'POST', body: blob })

[danawoodman]

Are you sure you can't override the content-type? I just added a test for it and passing { headers: { "Content-Type": "text/plain" } } and it works.

[danawoodman]

@kwhitley I've fixed the body issue in #18 as well as moved us to jsdom test env. I also added a test to verify the content-type header changing does work as intended

[kwhitley]

Thanks @danawoodman! Real quick on this, what would be the proposed way to send blob content? Currently, we attempt to JSON.stringify everything but FormData.

Currently in native fetch, you can do something like

fetch('/endpoint', {
  method: 'POST', 
  body: blob, // content-type is sent without explicitly defining
})

without having to explicitly define or override content-type... this allows you to easily pass files without extra steps. To support that in fetcher, we'd have to manually override the pre-embedded application/json header currently.

[kwhitley]

I'm leaning towards these behaviors:

• if payload is Blob, FormData, or other valid object type for passing straight to request.body, we pass it through to body unchanged, with no explicit content-type header
• else, we assume JSON and stringify/embed header

Thoughts? I just don't want to be more limiting than native fetch through our assumptions, nor make folks jump through hoops to even replicate what they were able to do easily before.

Ideal interface

const body = new Blob(['something here'],  { type: 'text/plain' })

fetcher().post('/endpoint', body)
// would be equivalent to
fetch('/endpoint', { method: 'POST', body })

[danawoodman]

@kwhitley you can send arbitrary body content now, see the tests here: https://github.com/kwhitley/itty-fetcher/pull/18/files#diff-2aa640fd9240ec144ac5019315d5631742a2b12d957395a0cc6ff4a0d9cf3f02R135. My change means you can manually pass in whatever body you want and we don't stringify it.

If you want to send a diff type, I don't see passing a header as a big deal?