test(db): cover pruneExpiredRecords' two defensive ?? 0 fallback arms

[RealDiligent]

Summary

src/db/retention.ts's pruneExpiredRecords guards two D1 driver anomalies with ?? 0 — the dry-run count row (line 75) and the delete-loop meta.changes (line 85) — and neither had direct coverage, even though the identical pattern on the sibling dedupeSignalSnapshots already has dedicated tests (lines 236-264). This mirrors that precedent exactly rather than inventing a new mocking style.

Three cases added:

Case	Arm	Assertion
count query returns no row	row?.n ?? 0	deleted === 0, not NaN
row present but n: null	row?.n ?? 0	deleted === 0
delete run() result lacks meta	result.meta?.changes ?? 0	deleted === 0, not NaN

Worth flagging: the line-85 guard prevents an infinite loop, not just a NaN

While revert-proofing I removed each ?? 0 to confirm the tests actually detect its absence. Removing the line-75 guard fails the test cleanly, as expected. Removing the line-85 guard does something more serious: changes becomes NaN, and since every NaN comparison is false, the loop's exit condition

if (changes < batchSize || deleted >= maxPerTable) break;

never fires — the batched delete loop spins forever. My local run had to be killed on timeout.

So that ?? 0 is load-bearing beyond producing a tidy number, and the new test's failure mode for that arm is a hang rather than an assertion error. I'm noting this rather than quietly leaving it: a hang is a worse CI signal than a failure, and a maintainer may decide the loop deserves its own Number.isFinite guard. I have not changed the loop — the issue is scoped to test coverage only, and adding a production guard here is a behavior decision that needs a maintainer's read.

Closes #8370

Scope

• The PR title follows type(scope): short summary Conventional Commit format, for example fix(api): restore profile access checks.
• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked a currently open issue this PR resolves (e.g. Closes #123) — a linked open issue is required for every contributor PR.

Validation

• git diff --check
• npm run actionlint
• npm run typecheck
• npm run test:coverage locally; codecov/patch requires ≥99% coverage of the lines AND branches you changed (aim for 100% on your diff so CI variance does not fail near the threshold). Global coverage is a non-blocking trend with a loose 90% backstop, not the gate.
• npm run test:workers
• npm run build:mcp
• npm run test:mcp-pack
• npm run ui:openapi:check
• npm run ui:lint
• npm run ui:typecheck
• npm run ui:build
• npm audit --audit-level=moderate
• New or changed behavior has unit/integration tests for new branches, fallback paths, and sanitizer boundaries

If any required check was skipped, explain why:

• Test-only diff (one file, +50 lines): no workflow, MCP, UI, worker, or dependency surface is touched. Root tsc --noEmit is clean and git diff --check passes. codecov/patch has no changed production lines to score; the scoped run emits a non-empty coverage/lcov.info containing src/db/retention.ts (the suite imports it directly), satisfying the "Verify coverage report exists" step.
• Pre-existing unrelated failures: test/unit/retention.test.ts's "dry-run reports eligible rows per table without deleting anything" and "deletes rows older than the window and keeps recent ones" fail on my local checkout. I verified they fail identically with my changes stashed, so they are environmental and untouched by this PR; my three new cases pass, and src/db/retention.ts is byte-unmodified (git diff --stat empty).

Safety

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• Public GitHub text stays sanitized, low-noise, and does not imply compensation guarantees or optimization tactics.
• Auth, cookie, CORS, GitHub App, Cloudflare, or session changes include negative-path tests.
• API/OpenAPI/MCP behavior is updated and tested where needed.
• UI changes use live API data or real empty/error/loading states, not production mock/demo fallbacks.
• Visible UI changes include a UI Evidence section below with JPG/JPEG or PNG screenshots arranged as organized, captioned, clickable thumbnails. SVG screenshots are not used as review evidence. Review-only screenshots or recordings are not committed to the repository.
• Public docs/changelogs are updated where needed; changelogs are only edited for release-prep PRs.

UI Evidence

Not applicable — unit-test additions; no visible UI, frontend, docs, or extension change.

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

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Tip

✅ LoopOver review result - approve/merge recommended

_{Review updated: 2026-07-24 19:07:03 UTC}

1 file · 1 AI reviewer · no blockers · readiness 100/100 · CI green · clean

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
This PR adds three unit tests mirroring the existing dedupeSignalSnapshots pattern to cover the two `?? 0` defensive fallback arms in pruneExpiredRecords (count-row-missing and meta-missing on the delete loop), closing #8370. The tests are well-targeted, mock env.DB directly to exercise the exact conditions that trigger each fallback, and the PR description transparently documents that the author verified via revert-testing that removing the line-85 guard causes an infinite loop rather than just a NaN, which is a valuable finding left for a maintainer decision rather than silently patched. The diff is test-only, closes a linked issue, and follows the sibling test's established mocking convention exactly.

Nits — 4 non-blocking

• The PR correctly scopes itself to test coverage only, but per its own finding that the line-85 guard prevents an infinite hang (not just a cosmetic NaN), consider filing or linking a follow-up issue for a `Number.isFinite`/explicit guard so this load-bearing behavior isn't left solely dependent on the `?? 0` never being touched by a future refactor.
• test/unit/retention.test.ts: the three new tests duplicate the mock-env boilerplate already established for dedupeSignalSnapshots almost verbatim — consider extracting a shared `mockD1({first, run})` helper if this pattern gets a fourth use, though at three call sites this is optional.
• File or reference a maintainer-facing issue for the `Number.isFinite`-style hardening on the line-85 `changes` value, as the PR description itself recommends, so the finding isn't lost after merge.
• Consider a small comment or follow-up test asserting `deleted` stays finite across repeated loop iterations if the guard is ever hardened, to lock in the hang-prevention behavior explicitly rather than only implicitly via the `?? 0`.

Decision drivers

• ✅ Code review — No blockers (1 reviewer)
• ✅ Gate result — Passing (No configured blocker found.)

Context & advisory signals — never blocks the verdict

Signal	Result	Evidence
Linked issue	✅ Linked	#8370
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 366 registered-repo PR(s), 146 merged, 37 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	RealDiligent; Gittensor profile; 366 PR(s), 37 issue(s).
Improvement	ℹ️ Insufficient signal	risk: clean · value: insufficient-signal · LLM: minor

Linked issue satisfaction

Addressed
The PR adds three tests directly mocking env.DB to trigger both the dry-run row?.n ?? 0 fallback (line 75) and the delete-loop meta?.changes ?? 0 fallback (line 85), asserting deleted === 0 rather than NaN, mirroring the sibling test pattern as requested with no production code changes.

Review context

• Author: RealDiligent
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 366 PR(s), 37 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Keep the PR focused and include validation evidence before maintainer review.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

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_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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