Handle none value for OTEL_PROPAGATORS

[Annosha]

Fixes #4143 OTEL_PROPAGATORS does not support "none" value #4143

Description

This PR introduces changes to the test suite to verify the behavior of the OTEL_PROPAGATORS environment variable when set to "none". The following updates were made:

1. Added a new test case:

Verifies that when OTEL_PROPAGATORS="none", no propagators are loaded, and the list of propagators is empty.

2. Modified test setup:

Reloaded the opentelemetry.propagate module in the new test to apply the environment variable settings and trigger the correct propagator configuration.
These changes ensure that:

When OTEL_PROPAGATORS="none", propagators are an empty list.
Default propagators (tracecontext, baggage) are not loaded whenOTEL_PROPAGATORSis set to "none".
The existing tests for default and non-default propagators remain intact.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

tox test keeps on running forever. I'm wondering if there are instructions for specific tests?

Successfully ran:

tox -e py312-test-opentelemetry-api
tox -e py312-test-opentelemetry-sdk

tox -e ruff

.tox\lint\Scripts\black . 
.tox\lint\Scripts\isort . 

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR: Will open a PR once the code changes are approved.
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[Annosha]

@lzchen @xrmx Please check the changes and provide your valuable feedback

[Annosha]

@xrmx Sorry about the redundant imports. Please check the changes.

[xrmx]

@xrmx Sorry about the redundant imports. Please check the changes.

Are you running tests locally? Please do that before asking people to review. Also please take a look at CONTRIBUTING.md and run linting tools too.

[Annosha]

@xrmx I ran both tox -e opentelemetry-api and tox -e opentelemetry-sdk and tox -e ruff for lint errors. I hope the tests will pass now.
Apologies for the inconvenience, I was working on multiple otel-language-sdks and somehow missed the steps.

[emdneto]

I ran this test locally, and it doesn't fail against the main branch

[Annosha]

@emdneto I apologize for the confusion. Could you clarify what you would like me to address?

[xrmx]

@Annosha The test should fail on main and raise and exception (as reported in the issue). If it doesn't fail with the current code it means it's not a good test to evaluate if the fix is working.

[Annosha]

@xrmx and @emdneto The test is failing after fixes in testing logic. This failure confirms that the test accurately detects the issue. Here is the test log on my machine:

Could you please review this on your end and advise on any further improvements needed?

[emdneto]

I was expecting something like that: this should fail when running against main with the ValueError present on the issue

        global_textmap = propagate.get_global_textmap()
        self.assertIsInstance(global_textmap, composite.CompositePropagator)
        self.assertEqual(len(global_textmap._propagators), 0)

[emdneto]

@xrmx I ran both tox -e opentelemetry-api and tox -e opentelemetry-sdk and tox -e ruff for lint errors. I hope the tests will pass now. Apologies for the inconvenience, I was working on multiple otel-language-sdks and somehow missed the steps.

The test is tox -e py312-test-opentelemetry-api

[Annosha]

@xrmx @emdneto indeed the commands I used were tox -e py312-test-opentelemetry-api and tox -e py312-test-opentelemetry-sdk for py 3.12
Lint checks are complete too. Please review the code and let me know if further changes are required. TIA