Allow configuring axios, this enables eg passing an axios adapter which runs outside of node

[nfcampos]

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[zeke]

Hey @nfcampos 👋🏼 Thanks for the PR.

I heard about you from @hwchase17, whom I met last night at a meetup. I'm guessing you're proposing this change in relation to @cbh123's PR to add Replicate support to langchainjs? langchain-ai/langchainjs#510

A couple thoughts:

• Can you explain what this is useful for? You're alluding to it in the PR title, but it would be useful to have more clarity around the purpose of this change. I'm guessing it's useful for testing, so you make a mock client that doesn't actually make HTTP calls. Is that right?
• Exposing an option like this kind of binds us to using axios, which might make it harder to move to another HTTP client, if we ever want to do that... like fetch. I have no intention of doing this, but thought I'd surface it. @mattt what do you think?
• If we wanna ship this, we should document it in the README.

[mattt]

• Exposing an option like this kind of binds us to using axios, which might make it harder to move to another HTTP client, if we ever want to do that... like fetch. I have no intention of doing this, but thought I'd surface it. @mattt what do you think?

The decision to use axios was entirely pragmatic — it was the first thing I got working, so I went with that. I'd be very open to dropping it entirely for fetch if that works cross-platform reasonably well.

Speaking more directly to this PR: How we make HTTP requests is an implementation detail that we shouldn't expose to the public API. If we want users to configure how this is done, we should advise them to replace client.request with their preferred method.

[nfcampos]

The only purpose this would serve for me (LangChain) is precisely to replace the implementation with a fetch-based adapter, so that this can be used outside Node. We already do this with the openai sdk which also (unfortunately) uses axios.

I agree with your comments re: not wanting to be tied to axios, this was just a lot less work for me than rewriting your whole library to use fetch

[mattt]

@nfcampos I got halfway through writing a response to your comment before deciding to do the exercise of swapping out the request implementation myself. There's a PR to swap out axios with polyfilled fetch here: #31. Please take a look when you have a chance 😃

[mattt]

Closing in favor of #31

Thanks for your help with this, @nfcampos!