ALEF-PAT-019

zero-as-falsy-id

guard × identifier-truthiness-conflation · severity 5 · confidence 0.85

JavaScript/TypeScript guards like `if (!id)` reject the legitimate value `0` because zero is falsy. Affects any code path where id=0 is a valid record identifier.

diagnosed in the wild

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healed by ALEF

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cited in posts

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observable signature

{
  "code_regex": "ifs*(s*!s*(session|user|item|product|order|account|row|message|token)?[Ii]ds*)",
  "alt_regex": [
    "ifs*(s*!s*w*[Ii]ds*&&",
    "sessionIds*||s*w*[Ii]ds*??",
    "returns*!s*[a-zA-Z]+[Ii]ds*;"
  ],
  "applies_when": "identifier is numeric AND 0 is a valid value (e.g., row 0, message 0, system user 0)",
  "does_not_apply_when": "identifier is string-typed (UUIDs, base64url, Lucia session strings, etc.) — !id correctly rejects only null/undefined/empty-string"
}

verified instances (3) — from the catalog

fix archetypes

explicit-null-checkcost: tiny
if (id == null) instead of if (!id)
branded-id-typecost: medium
RequestId = Branded<number|string,'RequestId'> with isPresent predicate

cite as

# In a PR description / issue / RFC:
fixes pattern ALEF-PAT-019 (zero-as-falsy-id)
ref: https://n50.io/patterns/019

# Machine query:
GET https://n50.io/api/patterns/019

# Scan your repo for this pattern:
npx @alef-prime/audit-agent-system . --pattern=019