Nicer error when specifying non-nil non-string opt value

[brandur]

Previously, if you specified a non-nil non-string opt value, like a
symbol for idempotency_key, you'd get a pretty user-unfriendly error
from Net::HTTP:

/Users/brandur/.rbenv/versions/2.4.5/lib/ruby/2.4.0/net/http/header.rb:21:in `block in initialize_http_header': undefined method `strip' for :foo:Symbol (NoMethodError)

Here, we introduce a new argument error that makes it a little easier
for someone to read. The impetus for the change is that we had an
internal product quality report where someone ran into this and was
confused.

I'm pretty sure this change is backward compatible because Net::HTTP
would call strip on anything that was passed in as a value, and
generally just strings would support that. There may be some other less
common data type that was accidentally compatible that someone was
using, but that case should be quite unusual.

r? @ob-stripe

[ob-stripe]

👍

[ob-stripe]

Hm, it looks like the tests are failing in 2.3. Maybe the stdlib didn't strip out nil values in 2.3 and did in later versions? Should we do that ourselves then?

[brandur-stripe]

Maybe the stdlib didn't strip out nil values in 2.3 and did in later versions? Should we do that ourselves then?

Ah yeah, you're right. I can see the argument for doing it in the API library given that I think that's what we do for nil parameters that are specified.

That said, I think I'm just going to punt on this for now by removing that one line from the test case. In newer versions of Ruby, Net::HTTP's default behavior is pretty reasonable: it strips the nil for you, but then emits a warning, which seems fine.

It someone asks for nil filtering down the line and has a good reason to want it, we can add it in then.

[brandur-stripe]

Thanks!

[brandur-stripe]

Released as 5.6.0.