biome-anti-slop

Opinionated Biome GritQL rules that reject low-evidence and low-signal TypeScript patterns.

The rules are vendored into each repository. Teams can review them, change them, and keep their lint policy next to their code.

Install with an agent skill

npx skills add norbertbodziony/biome-anti-slop --skill biome-anti-slop

Then ask your coding agent:

Install biome anti-slop in this repository.

The skill copies the rules into tools/biome/anti-slop, merges them into the existing Biome configuration, enables the native anti-slop profile, preserves project-specific settings, and validates the result.

To inspect the skill before installing it:

npx skills add norbertbodziony/biome-anti-slop --list

Rules

no-chained-type-assertions — rejects nested type assertions that discard type evidence.
no-conditional-empty-object-spread — rejects conditional spreads that use {} to omit fields.
no-known-value-widening — rejects explicit broad annotations on known values.
no-module-mocking — rejects Vitest and Jest module mocking in favor of dependency seams.
no-object-parameters — rejects the broad object type on function inputs.
no-reflect-apply — rejects Reflect.apply in favor of typed calls.
no-reflect-get — rejects Reflect.get in favor of typed property access.
no-runtime-typeof — requires boundary parsing instead of ad hoc typeof narrowing.
no-shape-in-symbol-names — rejects shape in symbol names.
no-unknown-returns — rejects functions that expose unknown to callers.
no-unknown-type-aliases — rejects aliases that conceal unknown.
no-unsafe-dictionary-type — rejects broad dictionary value contracts.

Native Biome rules

The skill also enables these built-in rules as errors, so their native implementations do not need to be duplicated as GritQL plugins:

complexity/noBannedTypes
complexity/noUselessTypeConstraint
nursery/noMisleadingReturnType
nursery/noUnsafeTypeAssertion
nursery/useReduceTypeParameter
style/noNonNullAssertion
style/useAsConstAssertion
suspicious/noExplicitAny

The nursery rules are intentionally strict. They reject non-const type assertions, misleadingly wide return types, and asserted reduce accumulators. Enabling the type-aware return rule activates Biome's scanner and type inference.

Manual installation

Copy rules/ into your repository, for example at tools/biome/anti-slop/rules/, then add every .grit file to the top-level plugins array and enable the native anti-slop rules in biome.json or biome.jsonc:

{
  "plugins": [
    "./tools/biome/anti-slop/rules/no-chained-type-assertions.grit",
    "./tools/biome/anti-slop/rules/no-conditional-empty-object-spread.grit",
    "./tools/biome/anti-slop/rules/no-known-value-widening.grit",
    "./tools/biome/anti-slop/rules/no-module-mocking.grit",
    "./tools/biome/anti-slop/rules/no-object-parameters.grit",
    "./tools/biome/anti-slop/rules/no-reflect-apply.grit",
    "./tools/biome/anti-slop/rules/no-reflect-get.grit",
    "./tools/biome/anti-slop/rules/no-runtime-typeof.grit",
    "./tools/biome/anti-slop/rules/no-shape-in-symbol-names.grit",
    "./tools/biome/anti-slop/rules/no-unknown-returns.grit",
    "./tools/biome/anti-slop/rules/no-unknown-type-aliases.grit",
    "./tools/biome/anti-slop/rules/no-unsafe-dictionary-type.grit"
  ],
  "linter": {
    "rules": {
      "complexity": {
        "noBannedTypes": "error",
        "noUselessTypeConstraint": "error"
      },
      "nursery": {
        "noMisleadingReturnType": "error",
        "noUnsafeTypeAssertion": "error",
        "useReduceTypeParameter": "error"
      },
      "style": {
        "noNonNullAssertion": "error",
        "useAsConstAssertion": "error"
      },
      "suspicious": {
        "noExplicitAny": "error"
      }
    }
  }
}

Biome >=2.5.9 <3 is required. Exclude the vendored directory from routine formatting so local checks do not rewrite copied policy files.

Development

bun install --frozen-lockfile
bun run check
bun run sync:skill
npx skills add . --list

The development tooling and tests use TypeScript. src/install.ts is the canonical installer; bun run sync:skill compiles its zero-dependency JavaScript runtime for skill users. rules/ is canonical, and CI verifies that the bundled installer and rule copies stay byte-for-byte current.

Releases

Versioned releases are built from vMAJOR.MINOR.PATCH tags. Each release includes a source archive and SHA-256 checksum after the full CI suite passes. See docs/RELEASING.md for the maintainer workflow.

License

MIT. See THIRD_PARTY_NOTICES.md for third-party notices.

Biome Anti Slop

At a glance

README