env-non-null-assertion
Non-null assertion on env vars can cause runtime crashes
Applies to: JavaScript, TypeScript
Why this matters
Using process.env.VARIABLE! assumes the environment variable is always defined, but this is often not true in development, CI, or new deployments. If the variable is missing, you'll get undefined behavior instead of a clear error. Validate environment variables at startup with a schema validator like Zod or t3-env.
Catch it before it ships
pip install stablestack # or: npx stablestackstablestack # scans your project, TYPE009 includedstablestack explain TYPE009TYPE009 is part of the Pro rule set. See pricing — the free tier ships 24 checks with no signup.
False positive in your codebase? Suppress a single line with # noqa: TYPE009
More Type Safety checks
weak-typing
Weak typing pattern (Dict[str, Any], List[Any]) loses type safety.
TYPE002naked-dict-for-structured-data
Using plain dict for structured data instead of dataclass/TypedDict.
TYPE004missing-type-hints
Function is missing type hints.
TYPE005inline-type-definition
Inline type definition instead of using shared/generated types.
TYPE006dict-type-inconsistency
Dict return type annotation doesn't match actual value types being assigned.
TYPE007duplicate-type-definition
Type definition may be duplicated across files.
TYPE008typescript-any
Explicit 'any' type defeats TypeScript's type safety
TYPE010unsafe-json-parse
JSON parsing with type assertion lacks runtime validation