Warning message `Calling set_status() on an ended span` in examples and tests

[condorcet]

Describe your environment
Python 3.6, 3.7, 3.8
Code in master, hash: a89bbc8

Steps to reproduce
Add logging to stdout in pytest.ini

[pytest]
log_cli = true
...

and run tests

OR

Run tracing example https://github.com/open-telemetry/opentelemetry-python/tree/8fa21e6bcbb0b28917039661ca2ba369d0dee6b2#tracing

What is the expected behavior?
No warning messages in positive tests and examples.

What is the actual behavior?
Multiple warning logs:
opentelemetry.sdk.trace:__init__.py:287 Calling set_status() on an ended span.

Additional context
It happens because we call set_status after ending a span

opentelemetry-python/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

Line 268 in 8fa21e6

self.set_status(Status(canonical_code=StatusCanonicalCode.OK))

which check if the (already ended) span is ended

opentelemetry-python/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

Line 286 in 8fa21e6

if has_ended:

[condorcet]

@ocelotl As I can see another bug correlated with this: default status of ended span must be 'OK' according to spec https://github.com/open-telemetry/opentelemetry-specification/blob/ccbf36374730488548703a65af40d9051d7ab944/specification/api-tracing.md#set-status, but now it's None

[ocelotl]

Thanks for reporting, @condorcet . We are aiming to have the span status set to None as long as it is not ended. Once it is, it should be set to OK unless the user specifically has it set otherwise. I'll take a look at this issue to figure out why this is not happening.