Add select_filing_status_value utility function

[MaxGhenis]

Summary

• Adds select_filing_status_value() utility function to simplify filing status selection
• Uses SINGLE as default (per IRS SOI data showing it's the most common status)
• Demonstrates pattern with 5 state income tax files

Changes

New utility function in tools/general.py

def select_filing_status_value(filing_status, filing_status_values, input_value=None, **kwargs):
    """Select a value based on filing status, with SINGLE as the default."""

Files refactored to use the utility (first batch)

State	File	Lines saved
MD	md_income_tax_before_credits.py	~12
CA	ca_income_tax_before_credits.py	~14
NY	ny_main_income_tax.py	~16
AL	al_income_tax_before_non_refundable_credits.py	~14
GA	ga_income_tax_before_non_refundable_credits.py	~12

Before

return select(
    [
        filing_status == statuses.SINGLE,
        filing_status == statuses.SEPARATE,
        filing_status == statuses.JOINT,
        filing_status == statuses.SURVIVING_SPOUSE,
        filing_status == statuses.HEAD_OF_HOUSEHOLD,
    ],
    [
        p.single.calc(taxable_income),
        p.separate.calc(taxable_income),
        p.joint.calc(taxable_income),
        p.surviving_spouse.calc(taxable_income),
        p.head_of_household.calc(taxable_income),
    ],
)

After

return select_filing_status_value(filing_status, p, taxable_income)

Test plan

• Added test file test_filing_status_utility.yaml with MD income tax tests
• Tests single, joint, and head of household filing statuses

Follow-up work

~40 additional state tax files can be migrated to use this utility in follow-up PRs.

Relates to #1176
Extracted from #6286

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (7e781d3) to head (19835f5).
⚠️ Report is 25 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##              main     #7243    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           12         5     -7     
  Lines          205        76   -129     
  Branches         0         1     +1     
==========================================
- Hits           205        76   -129     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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[PavelMakarchuk]

I like the simplification. Question: does this only work with scale parameters (single amounts, marginal rates)? If not, can we have an example of a select function without a scale parameter