feat(#3318): ban the constructs Semgrep cannot parse, taking the allowlist from 169 to 3

[thatskiff33-agents]

Linked Issue

• Closes or relates to: Closes SECURITY TOOLING: ban the Semgrep-unparseable generic-import-type call, and empty the unparsed allowlist #3318. Child of epic MEP PROGRAMME: maintainability, mechanical enforcement and codebase hygiene #2680; follow-up to SECURITY TOOLING: Make Semgrep coverage honest and align Cloud to the repository ruleset #2842, which shipped the coverage gate this empties.

Summary

#2842 made Semgrep's parse coverage honest: it measured which files the scanner could
not fully read, gated the number so it cannot grow silently, and left an allowlist of
169 files as the worklist. This empties that worklist by banning the constructs at
source instead of cataloguing them. The allowlist is now 3.

The three survivors are a bare & inside a string literal, which has no safe rewrite —
one of them is asserted with toHaveAttribute, so changing the string changes what the
test checks. An empty list needs an upstream parser fix, and this pull request does not
claim one.

The construct description was wrong again, and measuring it is most of the work here.
#2842 corrected the original filing from "a generic call with an import() type" to "the
EMPTY argument list", measured on a single-line repro. That correction was itself
incomplete. Measured against the pinned semgrep/semgrep:1.161.0 image with the exact
blocking config from ci.yml:

construct	result
f<typeof import("x")>()	fails — >() was unexpected
f<typeof import("x")>( "x", ) on three lines	fails — , was unexpected
f<typeof import("x")>("x")	parses
f<typeof import("x")>("x", 1)	parses
new C<typeof import("x")>()	parses
(await f()) as typeof import("x")	parses, both argument forms

Ten of the eleven unexplained entries were the trailing-comma form. The multi-line
spelling is not the trigger; the trailing comma is. So the real rule is that the call must
stay re-readable as a comparison expression — empty parentheses break that, and so does a
trailing comma. Which side of the line a call falls on is therefore decided by print
width: a formatter reflowing a long call creates a new unscanned region with no change
of substance at all. Twelve call sites in the tree sit on that boundary, and for ten of
the 169 entries it was the only cause.

The eleventh was a third fault nobody had written down. An import() type in a
FUNCTION PARAMETER annotation, once it carries a type-argument list or an indexed access.
(i: import("x").A) parses; (i: import("x").A<null>), (i: import("x").A["k"]) and
(i: (import("x").A)["k"]) all fail; (i: (typeof import("x"))["k"]) parses. Every one
of them parses in a return position, a variable annotation, an interface property or a
type alias. That single line was the entire reason
adult-member-hosting-queue-merge.realdb.test.ts was allowlisted with no call shape in it
anywhere.

What shipped

A real ESLint rule, scan/no-semgrep-unparsable-import-type, registered in an
all-files block in eslint.config.mjs — not a no-restricted-syntax arm, because that is
switched off for every test file and tests are the entire population. Detection is
behavioural for both shapes. Only the autofix is name-gated, to importOriginal /
importActual / vi.importActual, whose declared signatures make (await f(args)) as T
type-equivalent. It refuses to fix an unknown callee, a non-awaited call, more than one
type argument, an optional call, a comment inside the rewritten expression, or the
parameter shape.

307 call sites in 188 files rewritten, and 5 parameter-position types named as
aliases.

The allowlist entry shape changed from a bare path to { file, reason }, with the
reason structurally required — the gate refuses an entry without one.

Decisions, and why

The rule bans each shape as a CLASS, not as the broken spelling. This is a deliberate
widening and you should know about it. 23 files held the "parses today" call spelling,
and every one of them was a single rename or reflow away from becoming an allowlist entry
of its own. Inside the parameter position the boundary is incoherent — a type argument or
an index breaks it, a return position does not — so enumerating the quirks is not
maintainable. This is the issue's original proposal #1 read literally. The issue body's
correction warned against describing those 23 as broken, and the rule's message states
the measured truth instead: your call may well parse today, and it is still reported,
because print width decides.

Why the reasons moved into the data. They used to live in a prose composition summary
beside the list, and both of its clauses had gone false: the gate's own
KNOWN_CONSTRUCTS said three ampersand files while docs/MAINTENANCE.md said four. The
script was right and the prose was wrong, and the classification inherited the wrong
count. A reason a gate refuses to accept as absent cannot drift away from its entry.

The allowlist lands at 3, not the 4 the issue predicted. page-go-to-xero.test.tsx
was on the list for the call shape; its &, inside a
https://go.xero.com/...?shortcode=!aBc12&redirecturl=... string, never tripped anything.
Removing the call shape removed the file.

A lint rule rather than absorbing the recurrence again. Measured across four events
while #2842 was in flight: a main sync brought four unparsed files and one dead
suppression; one sibling child brought a suppression; four siblings at once brought two
files; a later sibling brought one more. Three of those four were sibling children
rather than upstream syncs — so this is not an event to absorb once, it is anything
landing at all. Removing the growth at source is the structural fix INV-SSOT-001
prefers over a policed one.

Pros and cons

The gain is that the worklist is gone, the growth cannot recur, and the reason each
survivor exists is now data the gate enforces rather than prose beside it. The cost is a
wide, mechanical 201-file diff, and a rule that reports 23 call sites which parse today —
by design, and with the reason in the message, but a contributor who meets it will need
that sentence to make sense of it.

Tests Added Or Updated

src/lib/__tests__/semgrep-unparsable-import-type-guard.test.ts — 27 cases through the
shipped config: three spellings, the trailing-comma form, the parses-today form, five
parameter forms, five measured-clean negatives, exact autofix output for five inputs,
three fix refusals, and a severity check at seven representative paths. The coverage
gate's own suite gained cases for the required reason.

src/lib/__tests__/member-guest-add-call-sites.test.ts was NOT changed here — that was a
different lane.

Eleven mutation probes, all driven from bash with git status after each so no probe
could be left in the tree:

mutation	caught by
detection keyed on vi.importActual	canary threw, file red, exit 1
detection keyed on importOriginal	11 cases red
empty-args only — #2842's description	5 cases red: the trailing-comma and parses-today fixtures
no parameter arm	5 cases red
parameter arm narrowed to type-arguments	3 cases red
parameter check widened to any position	canary threw, file red
NewExpression swept in	1 negative red
fix loses its parentheses	5 autofix cases red
rule downgraded to warn	13 cases red
reason no longer required in the gate	1 case red
alias branch removed	survived — dead code, and it was deleted

That last row is the one worth reading: a probe that survives is a probe that found
something. The branch was unreachable and is gone.

Validation Commands Run

• Final authoritative scan at the final tree state: 4293 files scanned, 0 whole-file
  unparsed, 0 rules abandoned, exactly 3 partial, matching the allowlist. Gate exits 0;
  the scan itself exits 0 with 3 pre-existing suppressed findings.
• npm run db:generate, npm run lint (0 errors, 48 pre-existing warnings),
  npm run typecheck across all three projects — this is what proves the 307 casts
  type-equivalent — npm run knip, npm run docs:linkcheck, npm run docs:indexcheck,
  npm run quality:budget, and npx playwright test --list (192 tests, 45 files).
• npx vitest related over all 200 changed paths in 8 chunks, plus all 235
  disk-scanning census and contract suites by name through the fail-closed runner in 8
  chunks. That second half matters: a suite that reads src/ from disk has no import edge
  to what it scans, so vitest related cannot reach it, and this change edits 188 files.
• The rewrite was verified twice, two ways: the fixer performed it, then an
  independent replay through a separate parser pass and separate range arithmetic
  reproduced all 307 sites byte-identically after whitespace normalisation, with no site
  left in the tree.
• Line endings: all 201 changed files are w/lf, .gitattributes pins
  *.ts text eol=lf, and git diff --check is clean. The rewrite was done by
  eslint --fix, not by a text-mode script.
• Self-match: the rule's own source and its guard test contain the construct only inside
  strings and comments; npm run lint is clean on both, and Semgrep parses both fully.

npm run lint found a site the measurement had missed — e2e/admin-member-detail.spec.ts,
because the scan was src/ and scripts/ while the blocking config also reads e2e/.
Five parameter sites, not four. The rule caught what the measurement did not, which is
the argument for the rule.

Commands Not Run And Why

• Full npm test: PR CI owns it. The targeted gate here is deliberately two-part —
  vitest related for the module graph, plus every disk-scanning suite by name, because
  the graph cannot reach those.
• The Semgrep measurements are from local Docker runs of the pinned image, not from CI;
  CI re-measures on push and Static analysis gate is the arbiter.

Screenshots Or UI Evidence

N/A.

Security And Privacy Impact

This is a security-coverage change and it strengthens coverage. Before, 169 files were
partially unreadable to the blocking Semgrep gate, which means rules that should have run
over them did not — silently, because a partial parse still exits 0. That is now 3, each
with a recorded reason the gate will not let anyone drop. No authentication,
authorisation, session, token or privacy behaviour is touched.

Data Integrity Impact

None. No writer, query, transaction or column is changed. The three non-test source edits
are type-only.

Concurrency And Lock Impact

• N/A — no transaction, lifecycle, capacity, settlement, credit, webhook,
  cron, or concurrency-sensitive writer changed.
• Writer class(es), canonical lock key(s), and acquisition order: none changed. The diff touches three sensitive-path modules — src/lib/xero-operation-retry.ts, src/lib/xero-bulk-contact-sync.ts and src/lib/age-tier.ts — and all three edits are type-only: a named type alias replacing an inline import() type in a parameter annotation. No lock participant, key, tier or guarded transition is added, moved or re-keyed.
• Immutable pre-lock key source and mutable under-lock re-read: unchanged. No lock site is touched.
• Status-guarded claim and proof that a lost claim runs no side effect: unchanged. No guarded transition is touched.
• Relevant open/last-10 PR numbers, counterpart writers/tests, and compatibility evidence: SECURITY TOOLING: Make Semgrep coverage honest and align Cloud to the repository ruleset #2842 is the gate this empties and is the direct counterpart; its suite gained the reason cases here. The two dynamically-imported modules in the Xero retry and bulk-sync paths are STILL imported dynamically — the alias names the type, not the import — so load order and outbox behaviour are unchanged. npm run typecheck across all three projects is the compatibility evidence, and it is exactly the check a type-only edit can be wrong under.
• Provider calls inside a transaction (write None, or justify the bounded exception from docs/CONCURRENCY_AND_LOCKING.md): None.

N/A is not ticked because sensitive paths are in the diff, which is the right thing for
the gate to insist on even when every edit is a type name.

Single Source Of Truth

• New or moved definitions, and the one module each now lives in: the banned-construct
  rule has one home, the ESLint rule; each survivor's reason has one home, its own
  allowlist entry, structurally required. Five inline import() parameter types became
  named aliases in the file that uses them.
• If anything was copied rather than imported, or a guard was added instead of a
  structural fix: nothing was copied — a duplicated count was removed. The gate's
  KNOWN_CONSTRUCTS and docs/MAINTENANCE.md disagreed about the ampersand file count
  and the prose was wrong; the reasons now live in the data the gate reads. On "guard
  versus structural fix": the rule is the fix at source, and the SECURITY TOOLING: Make Semgrep coverage honest and align Cloud to the repository ruleset #2842 coverage gate stays
  as the measurement. They are not two enforcers of one rule — one stops the construct
  being written, the other reports what the scanner actually managed to read.

Payment Or Accounting Impact

None.

Migration Or Deployment Impact

None.

Docs Updated

• docs/MAINTENANCE.md — the third parser fault stated, the ampersand count corrected,
  and that two of the three shapes are now banned by lint rather than catalogued.

Changelog Entry

• Fragment added (changelog.d/<pr-number>-<slug>.md): yes.

Residual Risks

None. Every finding from the review round is fixed in this pull request.

Stated limits

• The Semgrep measurements are local Docker runs of the pinned image rather than CI runs.
  CI re-measures on push.
• Class-method and constructor-signature parameter positions are included by shape
  rather than individually measured, because none occurs in the tree. The config comment
  says so at the site.
• The allowlist is 3, not 0. Emptying it needs an upstream parser fix and this pull
  request does not claim one.

Manual Checks Required

None.

Safety Confirmation

• I did not use production credentials, production databases, production backups, or
  live provider endpoints. Every Semgrep run was a --rm container against the local
  tree.
• Merge handling follows the AGENTS.md "Completion and Merge" risk gate: this is a
  child of epic MEP PROGRAMME: maintainability, mechanical enforcement and codebase hygiene #2680 and targets the epic's integration branch under Epics reach main as one merge from an integration branch, and the fork upgrade contract gets stated where forks read it #3002. It does
  not merge to main on its own; the epic's single pull request into main is where
  this gets its owner review.

A process note that belongs in the record

Clearing a hung Semgrep container, this lane ran docker ps -q | xargs docker kill and
took another lane's pg-issue3292 Postgres with it. It was restarted immediately and its
port mapping survived, and a note went to that lane on #3292 so a transient database red
in that window is not diagnosed twice. A lane clears only the containers it started, by
name.

🤖 Generated with Claude Code

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