How to ignore PonyORM generator expressions in nose-tests coverage

Question

I'm using nosetests --cover-erase --with-cover --cover-branches to run my test cases.

I'm using PonyORM to delete set of objects. Below is how my code looks like.

@db_session
def remove_all_stuff(self):
    delete(j for j in MyEntityClass if j.deleted == True)

When I calculate the coverage, even though I execute remove_all_jobs. PonyORM doesn't execute the generator expression inside delete(.

How do I ignore the generator expression and still check that the delete( is called?

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What I found.

1. # pragma: no cover -> cannot be used because I need to cover delete
2. [report] exclude_lines in .coveragerc also doesn't work for this scenario.

Answer 1

I've added some other suggestions to the coverage.py issue about this.

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Some other possibilities of how to handle this more gracefully:

You can set the coverage.py pragma regex so that some lines are automatically pragma'd:

[report]
partial_branches = 
    pragma: no branch
    \.select\(lambda

Now any line that matches either of the two regexes will be considered partial-branch, so your line is recognized even without a comment.

You can separate the definition of the lambda or generator expression from the line that uses them:

to_select = lambda p: p.nom_d_exercice.lower().startswith(chaine.lower())    # pragma: no branch
return Praticien.select(to_select)

or:

to_delete = (j for j in MyEntityClass if j.deleted == True)  # pragma: no branch
delete(to_delete)

This isolates the non-run code to its own line, so you don't run the risk of turning off coverage measurement on a line that truly needs it.