UpdateUser wrote a new address but kept email_verified, so patching a verified
account asserted a proof of an address nobody had proven — and the
pre-session login mails and resolves on exactly that flag, so a typo'd edit
could hand the account's sign-in codes to the wrong mailbox.
Changing the address now clears the flag in the same write; a no-op patch that
passes the same value keeps it. The fake mirrors the semantics, and the pgint
suite pins both halves (same value keeps proof, new value drops it).
The design has claimed since migration 0010 that at most one account can hold
a PROVEN email address, with ErrEmailTaken as the 409 a second verifier sees.
Neither half ever shipped: no migration created users_verified_email_unique,
and VerifyEmailOTP had no guard at all — the sentinel was defined but never
returned, so two accounts could both verify one address. The damage is not
cosmetic: the pre-session login resolves accounts BY verified email, so the
duplicate decided which identity a mailed sign-in code belonged to.
- Migration 0020 creates the partial unique index (lower(email) WHERE
email_verified) the comments have been citing — the database-level backstop.
- VerifyEmailOTP now refuses the take-over with ErrEmailTaken BEFORE consuming
the code (the address, not the code, is the problem), charges no attempt,
and maps a lost cross-user race (unique violation) to the same answer.
- The verify handler answers 409 email_taken instead of a generic 500.
Covered by the pgint suite (sequential double-verify refused with the code
still live, a direct duplicate write still loses to the index, the refused
account can still prove its own address) and a hermetic 409 case.
The hermetic suites encode the store contracts against fakes; PGRepo drifted
behind them three times (attempt accounting, a missing JOIN, a missing FOR
UPDATE) while every unit test stayed green. This harness replays the real
embedded migrations onto a throwaway database — its name must contain "pgint"
or the harness refuses to run — and exercises the SQL directly: sessions, the
onboarding email-OTP lifecycle (supersede/expiry/lockout), the pre-session
login consume, the op-login state machine, link and bind-code redemption,
submissions, and builds with the image admission round trip.
Run it after touching SQL under internal/api/pgrepo.go, internal/submit, or
internal/build; CONTRIBUTING.md carries the one-liner.
Lemon-miaow