firebase/firebase-ios-sdk: technical due diligence, read from its repository

The median source file here is 77 lines. 43 files exceed 1,000 lines, the largest being 15,253. Size is not a defect on its own — some problems genuinely live in one place — but these are where merge conflicts, review fatigue and single-owner knowledge concentrate, and they are the first thing that slows an inheriting engineer down.

633 product files are in the new language and 467 are still in the old one, 114 months after the first new file appeared. The new language's share of the lines rose from 2% to 46%, and moved 6 percentage points in the last year. Two languages for one job doubles what an engineer has to know, and the unmoved half is usually what nobody wants to touch. Ask whether finishing it is planned, and what it costs.

Deleted lines per line added rose from 0.46 to 0.76 between the first and second halves of this history. Rework is normal and often healthy, but a rising ratio means an increasing share of the team's time is spent replacing code that already exists rather than building what does not. Whether that is deliberate repayment or churn is a question for the team.

The newest release, 13.1.1, is not on the branch this survey read; the newest release on it is 13.1.0. The shipped product may differ from what this report describes. Survey the release branch too.

Third-party code is committed into this repository without any statement of the terms it arrived under. Unknown terms are harder to deal with than inconvenient ones: an awkward licence can be complied with, an absent one cannot. Each of these needs its origin established before the code changes hands.