Option to find objects without throwing ObjectNotFoundError

[subhashb]

get and find_by methods in DAOs throw ObjectNotFoundError exception on zero results. It would be good to optionally control the exception raising behavior, as needed by the application functionality. Currently, the only way to find an object without raising an exception is with query.filter(<>).first.

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Behavior in other packages:

SQLAlchemy's get returns None if no record was found. Flask SQLAlchemy package has a get_or_404 method, which is like get() but aborts with 404 if not found instead of returning None.

Django's get raises DoesNotExist if no objects were found or MultipleObjectsReturned if more than one object was found.
There is no find_by method in Django.

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Options:

1. get as-it-is with find_by and find_first_by
find_first_by does not raise exception where as the other two do.
2. get as-it-is with find_by and find_by_or_raise
find_by does not raise exception, but find_by_or_raise
3. get as-it-is with find_by and query.filter(<>).first
get and find_by continue to raise exceptions (current behavior).

[abhirathmahipal]

For

Relevant links/discussions we had

• Failing sometimes is better than checking every time.
• Additional test cases to cover the Exception branch (or use #pragma: no cover)

Laying some context to why it'd be useful.

In the try/catch version, we need to test two branches.

try:
    user = user_repo.find_by_email_address('[email protected]')
except ObjectNotFoundError:
    return # or handle it by raising another exception

if user.created_at > datetime(2019):
    # do something
    pass

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In this version, we only need to test one.

user = user_repo.find_by_email_address('[email protected]')

# we need fewer test cases to reach desired coverage here
if user and user.created_at > datetime(2019):
    # do something
    pass