Use fetch inside Axios in the background

[fregante]

Extracted from:

• POC: Begin work on MV3 #2107

Context:

• Axios is based on XMLHttpRequest but that's not available in Service Workers
• This PR adds an adapter that uses fetch instead of XMLHttpRequest, only in the background page

Warnings:

• The adapter I found isn't well-tested nor used much, it's likely that it's not feature-complete
• This isn't actually required until we switch to MV3, but we could still merge it just to test it
• Not really tested, I'm just floating the idea first

The alternative to merging this is to:

• hope that Axios adds fetch support: Feature request: fetch based adapter axios/axios#1219
  • "…This is work up to a year…"
• swap Axios with a raw fetch (which would be my preferred solution, but maybe Axios does something fetch doesn't )

[fregante]

This appears to work in preliminary tests, including setting URL parameters, headers and POST body, using the HTTP Request brick.

I'd still classify this as an "experimental PR" due to the warnings I mentioned previously.

Before

Background page "Network" tab

After

[twschiller]

For the background we don't use much of the axios surface area (it's just JSON payloads, base URLs, header logic).

I'd probably lean toward an adapter so most programmers only need to reason about the Axios API? I'm also OK either using that library adapter or wring our own for the functionality we need (glancing at the adapter, the code is straightforward, and actually probably covers more features than we need)

The main benefits of Axios are around the automatic JSON handling, adapters, transforms, retry logic, etc. Looking at some docs there's also slight differences on how it determines whether a response is "ok", etc. But those probably won't matter for us in practice

[fregante]

I'd probably lean toward an adapter so most programmers only need to reason about the Axios API?

Yeah that's useful when writing tests. The current PR only enables fetch in the background because that's where it's needed by MV3.

If this already works for you it's easier than replacing Axios with Fetch (or other fetch-based library).

Merge at will — or not, we can alternatively only use it if it's running as MV3.

[twschiller]

Merge at will — or not, we can alternatively only use it if it's running as MV3.

I'm in favor of moving toward the more modern browser API. (And definitely against conditionally using fetch)

Reading more about XHR vs. fetch, looks some slight difference in CORS and passing along cookies which shouldn't impact us

Let's use this library for now. We'd like end up forking it or inlining it if we need to make any changes. Looks like it's not really maintained