Add Stripe client telemetry to request headers

[jameshageman-stripe]

Follows stripe/stripe-ruby#696 and stripe/stripe-php#549 in adding telemetry metadata to request headers.

The telemetry is disabled by default, and can be enabled like so:

stripe.enable_telemetry = True

[remi-stripe]

cc @stripe/api-libraries for awareness

[jameshageman-stripe]

Pinging @akropp-stripe @ob-stripe @brandur-stripe for review as you were all part of stripe/stripe-ruby#696.

The 2 failing tests are also failing on master and are unrelated to my changes.

[brandur-stripe]

Minor comment below, but generally LGTM! Thanks for following the same conventions set by the Ruby version.

OB's informally the main Python maintainer, so I'll leave final review to him.

[brandur-stripe]

Can you try to arrange this as alphabetically as possible (since it's already roughly in that order)? Just swap it with the line above.

[jameshageman-stripe]

Done!

[brandur-stripe]

Minor note, but the one in Ruby is called StripeRequestMetrics, and it'd be nice to standardize on a name. RequestMetrics is probably better given it's already in the Stripe namespace.

[jameshageman-stripe]

I'm fine either way, I just figured from stripe.stripe_request_metrics import StripeRequestMetrics was overly verbose.

[brandur-stripe]

Yeah, the Stripe prefix seems pretty redundant. Let's stick with what you have.

[brandur-stripe]

@ob-stripe I looked into the test failures that are happening on master a bit. They're caused because our TestPycurlClientHttpProxy and TestPycurlClientHttpsProxy classes inherit from TestPycurlClient and are calling that parent's check_call implementation (see the last line below):

class TestPycurlClientHttpProxy(TestPycurlClient):
     ...

    @pytest.fixture
    def check_call(self, request_mocks, curl_mock):
        def check_call(mock, meth, url, post_data, headers):
            ...

            super(TestPycurlClientHttpProxy, self).check_call(request_mocks)(
                mock, meth, url, post_data, headers)

Because all our check_calls are marked as @pytest.fixture, Python doesn't expect any explicit invocations, and therefore this error is triggered (I assume that something must have changed in some library because this seemed to be fine before).

I could fix this by just moving TestPycurlClient's check_call body into a new method (check_call_inner?) and just having check_call as well as TestPycurlClientHttpProxy and TestPycurlClientHttpsProxy call that, but I'm not sure that's a "clean" solution. Can you think of a better way?

[ob-stripe]

@jameshageman-stripe Can you rebase on the latest master? I fixed the unrelated test error.

@brandur-stripe Oops, sorry, I'm only seeing your comment now! FWIW I initially went with your suggestion, but changed my mind to make the new method slightly more consistent with what we already do in TestRequestsClient.check_call.

[brandur-stripe]

@brandur-stripe Oops, sorry, I'm only seeing your comment now! FWIW I initially went with your suggestion, but changed my mind to make the new method slightly more consistent with what we already do in TestRequestsClient.check_call.

NP. Your fix ended up being better than what I was imagining.

[jameshageman-stripe]

@ob-stripe Rebased: all tests are passing except pypy3, which is failing with ImportError: cannot import name 'pythonapi'. This appears to be happening on master as well, so I'd say it is unrelated to this PR's changes.

[jameshageman-stripe]

r? @ob-stripe

[ob-stripe]

Could you add from __future__ import absolute_import, division, print_function at the beginning of the file? Even though that line won't do anything here, it's present in all source files to prevent Python 2/3 compatibility issues.

[ob-stripe]

Requested one minor change, but otherwise LGTM!

@ob-stripe Rebased: all tests are passing except pypy3, which is failing with ImportError: cannot import name 'pythonapi'. This appears to be happening on master as well, so I'd say it is unrelated to this PR's changes.

Yes, this is an issue with pipenv that will be fixed in the next version. Sorry, should have let you know that was expected!

[jameshageman-stripe]

@ob-stripe Done!

[ob-stripe]

@jameshageman-stripe Thanks! Mind squashing the commits before I merge and cut a release?

[jameshageman-stripe]

@ob-stripe squashed

[ob-stripe]

Released as 2.18.0.