GermanDZ 7c14c80444 Fix SimpleFIN inverting Loan account balances (#1574) ...

* Fix SimpleFIN inverting Loan account balances

SimplefinAccount::Processor#process_account! routes every liability
through OverpaymentAnalyzer + normalize_liability_balance. That path
is built around credit-like liabilities, where transaction history
distinguishes debt vs. credit. For a Loan account with only the
opening anchor (no payment history), the analyzer returns :unknown
and the fallback negates the observed value:

    def normalize_liability_balance(observed, bal, avail)
      ...
      -observed
    end

That's wrong for loans: the bank reports the principal outstanding
as a positive number from its own books. Negating it stores the loan
balance as negative, so BalanceSheet#net_worth = assets - liabilities
ends up _adding_ the loan instead of subtracting it (off by 2× the
loan amount). Example with a hypothetical mortgage:

  raw_balance       = 100000.00  (positive — bank's own report)
  Sure stored       = -100000.00 (negated by the fallback)
  Net worth shown   = inflated by 2 × 100000

Short-circuit Loan accountables straight to observed.abs and skip the
analyzer/fallback entirely. Loans don't have credit-vs-debt
ambiguity — if the loan is paid off the balance is 0, not negative.
Credit cards still go through the existing heuristic.

* Add observability for the SimpleFIN loan sign branch

Mirrors the logging + Sentry breadcrumb the credit-card branches emit
when the OverpaymentAnalyzer classifies as :credit / :debt, so the
loan short-circuit shows up in production traces too. Per CodeRabbit
review on #1574.

* Test that positive bank-reported loan balances are preserved

The existing "inverts negative balance for loan liabilities" test only
covers a bank that reports the loan as negative — both the old (buggy)
fallback and the new short-circuit produce the same +50000 there, which
is why the inversion bug went undetected. Add a sibling test where the
bank reports +50000 (the common mortgage convention); under the old
code that became -50000 and inflated net worth.

* Redact monetary amounts from SimpleFIN liability info logs

Move raw observed/stored amounts and metric totals from `Rails.logger.info`
and `Sentry.add_breadcrumb` payloads to a `Rails.logger.debug` line.
The info-level message and breadcrumb data now carry only identifiers
(`sfa_id`) plus the classification (`loan` / `credit` / `debt` /
`unknown`) and `tx_count`, so log aggregators and Sentry no longer
receive raw monetary values for any of the four liability branches.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-04-29 13:00:38 +02:00

7.6 KiB

Raw Blame History

View Raw