[derrickaw]

The flaky YamlTransformE2ETest.test_empty_inputs_throws_error test and other three related had incorrect context manager nesting causing the flaky tests. In CI, the thought is that _schema_transforms is populated by Protobuf descriptors due to being cached globally. When p.run() is executed in these incorrectly nested pipelines, cloudpickle tries to serialize the providers and hits the Protobuf descriptors and crashes. The CI situation surfaces the nesting context manager issue, but doesn't cause it.

Simulate CI:

cd <your_path>/beam/sdks/python
python -c "
import pytest
from apache_beam.yaml.yaml_provider import standard_providers
from apache_beam.transforms.external import SchemaTransformsConfig
from apache_beam.portability.api import schema_pb2

providers = standard_providers()
for p_list in providers.values():
  for p in p_list:
    if hasattr(p, '_schema_transforms'):
      p._schema_transforms = {
          'mock': SchemaTransformsConfig(
              identifier='mock',
              configuration_schema=schema_pb2.Schema.DESCRIPTOR,
              inputs=[],
              outputs=[],
              description=''
          )
      }
      break
  if any(hasattr(p, '_schema_transforms') and p._schema_transforms for p in p_list):
    break

pytest.main(['apache_beam/yaml/yaml_transform_test.py', '-k', 'test_empty_inputs_throws_error', '-o', 'rootdir=.'])
"

In master: fails with similar error about descriptors.
In this branch: passes

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.12%. Comparing base (83148cb) to head (581b708).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #40228      +/-   ##
============================================
+ Coverage     55.08%   55.12%   +0.04%     
  Complexity     1722     1722              
============================================
  Files          1076     1076              
  Lines        171844   172014     +170     
  Branches       1262     1262              
============================================
+ Hits          94660    94828     +168     
- Misses        74908    74910       +2     
  Partials       2276     2276              

Flag	Coverage Δ
python	79.84% <ø> (+0.03%)	⬆️

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[shunping]

Thanks! I think another possible direction could be how we can better handle globally-shared variable if the tests are heavily depending on it. Let's put that in our back pocket for now.