rosetta: Instructions file for GitHub Copilot

Extractor import side effects

There are two separate hazards here. Hazard 1 must be closed for every src/extract-*.ts file — and now is (audited 2026-07-14, issue #19). Hazard 2 is not closed for most extractors and isn't required to be; it's mitigated in tests by the import pattern described below.

1. No unguarded execution at module scope. Every extractor's side-effecting logic (DB writes, file/network reads, subprocess spawns) must live inside a main() function called only under if (import.meta.main) { ... }. Pure helpers, type declarations, and argument-shape parsing that has no I/O may stay at module scope. Without this guard, merely import-ing the file — e.g. a future test reusing a parser helper — runs the entire pipeline unconditionally. This was the actual gap found in the 2026-07-14 audit: extract-commands.ts, extract-devices.ts, extract-properties.ts, and extract-all-versions.ts had no import.meta.main guard at all. All extractors now have one.

2. Top-level db.ts import still opens a connection. db.ts does export const db = new sqlite(DB_PATH) at module scope, so any extractor that does import { db, initDb } from "./db.ts" at the top of the file opens a DB connection the moment it's imported — even with the import.meta.main guard in place, since the guard only defers execution, not the import itself. Most extractors keep this top-level import; it opens the real on-disk DB unless the importer set DB_PATH first. That's correct for normal CLI use (a real DB is exactly what you want), but it's a trap for any test or script that imports the module without first setting DB_PATH. This is not itself a bug to fix — it's the reason the test-import discipline below exists. For tests, that means:

   • Set process.env.DB_PATH = ':memory:' before importing the extractor.
   • Use dynamic await import(...) so Bun does not hoist the real-DB import before the env var assignment.
   • extract-schema.ts and extract-test-results.ts go further and dynamic-import db.ts itself lazily inside main(), so importing them touches no DB at all — that's the strictest form and is preferred for new extractors, but not required retroactively.

src/query.test.ts carries a singleton guard (V-db-wipe-guard in VALIDATION.md) that fails loudly if any test file leaves the db singleton pointed at a non-:memory: path — treat a failure there as a real regression in one of the two patterns above, not test flakiness.

That runtime guard only fires on the unlucky file order where the offending file loads db.ts first, so a static db.ts-reaching import can sit latent through many green runs and present as a CI flake (#98). src/source-hygiene.test.ts (V-test-db-import-static-guard) closes that gap structurally: it scans every *.test.ts that sets process.env.DB_PATH and fails if any statically (value-)imports a module transitively reaching db.ts, regardless of run order. Statement-level import type … from is erased by the transpiler and stays allowed (e.g. extract-hardware-catalog.test.ts); only value imports load db.ts. So the dynamic-import discipline above is now enforced, not merely documented — add a new DB_PATH-setting test the wrong way and this test rejects it at author time.