Some use-cases may require allowing an empty URL

Is your feature request related to a problem? Please describe.

I’d like to give some feedback for the axios 0.25 release. #3791 introduces a fast failure when an empty string is provided as a URL to the request builder. However, my own and at least one other project are intentionally using empty strings as URLs and the 0.25 release breaks working code. It is listed as a breaking change in the changelog, but the behavior may be unpractical for some use-cases: Let’s imagine a service abstraction over a RESTful resource; the baseURL could be something like http://example.com/examples, avoiding passing /examples as a path with each request. A GET or POST request using "" as a URL would be valid in this case.

Describe the solution you’d like

• Is it possible for the request builder to accept empty strings but fail for undefined?
• Or maybe some config option could be introduced to intentionally opt out of the fast failure.
• An obscure solution would be to additionally pass the baseURL as url to axios.create, but currently the presence of the URL is checked before merging the configs. Moving the if (!config.url) { part down after the config merge would allow this escape hatch.

I’d be happy to submit a PR if desired.

Describe alternatives you’ve considered

• Changing the respective occurrences in my code.
• Using a slash or a space as a URL would work in many cases but it would also introduce trailing slashes.

Additional context

[jasonsaayman]

We could potentially change the name to path, then make it not required, then this might make more sense, people can then implement baseUrl and leave out path. Does this sound like a better solution?

We can also use a mapper to allow some backward compatibility with url to start off with and then add warnings and remove.

[jasonsaayman]

Changes made with #4426 will release soon