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Informative error message when calling `add` over variables that don't exist

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
python
Domain
tooling

Research direction

Start by reproducing the failing add call over variables that do not exist, using the linked OpenFisca US run as the initial reference. Trace where the NoneType AttributeError occurs and define what informative error should replace it; done means the failure reports the missing variables clearly.

Written by the indexing model from the issue text.

Description

This log makes me think this is what it yields:

AttributeError: 'NoneType' object has no attribute 'entity'

Dominant language
Python
Stars
1
Forks
1
PR merge metrics
No merged PRs in 30d

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First steps

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  4. Open a pull request that references the issue number.

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