anti-slop

Opinionated Oxlint rules that reject low-evidence and low-signal TypeScript and JavaScript patterns.

Anti-slop is first and foremost the ruleset I use with my work, projects, and team. It reflects my preferences and taste rather than attempting to be a universal coding standard.

This project is meant to be vendored, not treated as a fixed npm dependency. There is no official npm package. Copy the rules into your repository, read them, and change them to match your team's standards. The bundled agent skill handles the initial copy and configuration; after that, the vendored files are yours to maintain and make your own. Community-maintained forks and packages are welcome, but their compatibility and release lifecycle belong to their maintainers.

Install with an agent skill

npx skills add dmmulroy/anti-slop --skill install-anti-slop

Then ask your coding agent to install or configure anti-slop in the current repository. The skill copies the plugin, installs compatible Oxlint dependencies—matching an existing Oxlint version when present—merges the plugin into the existing lint configuration, enables every generic rule, and validates the result. In repositories that depend directly on Effect, it also enables the opt-in Effect rule group.

Update an existing installation

Ask your agent to update anti-slop while preserving local customizations, optionally naming an upstream revision or selected fixes. The same skill stages incoming source separately, uses a three-way merge when the original upstream snapshot is recoverable, and otherwise ports reviewed changes conservatively. It preserves local rules and configuration, asks about conflicting policy and enabling new rules, and records provenance for future updates. It does not force-replace the vendored directory.

For latest upstream, ask the agent to retrieve and identify that revision; an already-installed skill bundle may be older. The copy script itself does not fetch or merge updates.

To inspect available skills first:

npx skills add dmmulroy/anti-slop --list

Manual local installation

Copy src/ into the target repository, for example at tools/oxlint/anti-slop/. If the repository already uses oxlint, install @oxlint/plugins at exactly the resolved Oxlint version. Otherwise, install the same current version of both packages. Keep both versions exact so upgrades move them together.

Register the copied entry point in oxlint.config.ts:

import { defineConfig } from "oxlint";

export default defineConfig({
  ignorePatterns: [
    ".agent/**",
    ".agents/**",
    ".claude/**",
    ".codex/**",
    ".continue/**",
    ".cursor/**",
    ".gemini/**",
    ".opencode/**",
    ".pi/**",
    ".roo/**",
    ".windsurf/**",
    "tools/oxlint/anti-slop/**",
  ],
  jsPlugins: [
    { name: "anti-slop", specifier: "./tools/oxlint/anti-slop/index.ts" },
  ],
  rules: {
    "oxc/no-accumulating-spread": "error",
    "anti-slop/no-array-filter-map": "error",
    "anti-slop/no-reduce-accumulator-copy": "error",
    "anti-slop/no-chained-type-assertions": "error",
    "anti-slop/no-conditional-empty-object-spread": "error",
    "anti-slop/no-known-value-widening": "error",
    "anti-slop/no-module-mocking": "error",
    "anti-slop/no-object-parameters": "error",
    "anti-slop/no-reflect-apply": "error",
    "anti-slop/no-reflect-get": "error",
    "anti-slop/no-runtime-typeof": "error",
    "anti-slop/no-shape-in-symbol-names": "error",
    "anti-slop/no-unknown-parameters": "error",
    "anti-slop/no-unknown-returns": "error",
    "anti-slop/no-unknown-type-aliases": "error",
    "anti-slop/no-unsafe-dictionary-type": "error",
    "anti-slop/no-widen-then-assert": "error",
    "anti-slop/require-readable-spacing": "error",
    "anti-slop/require-safety-comment-for-type-assertion": "error"
  }
});

The same ignorePatterns, jsPlugins, and rules work under lint in a Vite+ config. Merge the ignore patterns into Vite+'s fmt.ignorePatterns as well so vp check does not reformat installed agent assets or the vendored plugin. Preserve existing ignores and add any other project-local agent tooling directories detected in the repository; do not broadly ignore every dot-directory.

Optional Effect rules

Effect-specific rules live in a separate plugin so projects that do not use Effect do not inherit Effect architecture policy. Register the Effect entry point only in repositories that use Effect:

export default defineConfig({
  jsPlugins: [
    { name: "anti-slop", specifier: "./tools/oxlint/anti-slop/index.ts" },
    {
      name: "anti-slop-effect",
      specifier: "./tools/oxlint/anti-slop/effect/index.ts"
    }
  ],
  rules: {
    "anti-slop-effect/no-manual-effect-error-tag": "error",
    "anti-slop-effect/no-manual-tag-comparison": "error",
    "anti-slop-effect/no-manual-tagged-construction": "error",
    "anti-slop-effect/no-service-constructor-imports": "error",
    "anti-slop-effect/prefer-effect-match": "error"
  }
});

Rules

Generic rules

• no-array-filter-map — rejects adjacent eager array filter/map passes while allowing lazy iterator pipelines.
• no-reduce-accumulator-copy — rejects non-spread accumulator copies inside reducers; complements native oxc/no-accumulating-spread.
• no-chained-type-assertions — rejects nested as and angle-bracket assertions that fabricate evidence; chains made only of as const remain valid.
• no-conditional-empty-object-spread — reports object spreads that use a conditional {} branch to omit fields. It intentionally has no autofix because omission is not equivalent to assigning undefined.
• no-known-value-widening — rejects known expressions flowing into explicit unknown, object, anonymous-object, or open-dictionary targets, including known arguments passed to local unknown type predicates. Empty dictionary accumulators and finite-key Record targets remain valid.
• no-module-mocking — rejects Vitest and Jest mock, doMock, and unstable_mockModule calls in favor of real dependency seams.
• no-object-parameters — rejects object, unions containing it, and scoped or transparent generic aliases that resolve to it on function inputs.
• no-reflect-apply — rejects global Reflect.apply in favor of typed function calls.
• no-reflect-get — rejects global Reflect.get in favor of typed property access or boundary parsing.
• no-runtime-typeof — requires boundary parsing instead of ad hoc typeof narrowing. Existence probes against the string "undefined" are allowed, and type predicates can be enabled explicitly.
• no-shape-in-symbol-names — rejects the case-insensitive substring shape in locally owned symbol names while allowing static member names such as Zod's schema.shape that cannot be renamed locally.
• no-unknown-parameters — rejects unknown and unions containing it on function inputs except the explicit cause convention and the exact subject of a type predicate.
• no-unknown-returns — rejects explicit function contracts that resolve to unknown, Promise<unknown>, or PromiseLike<unknown>, including scoped and transparent generic aliases.
• no-unknown-type-aliases — rejects scoped and transparent generic aliases whose resolved type is unknown.
• no-unsafe-dictionary-type — rejects dictionary value contracts based on unknown, any, object, {}, and semantic equivalents. Generic constraints such as T extends Record<string, unknown> are allowed.
• no-widen-then-assert — rejects immutable local flows that widen known evidence to unknown, any, object, or a broad record and later assert it back to a narrower type.
• require-readable-spacing — autofixes missing blank lines between top-level declarations, around multiline bindings, before control flow/returns, and after blocks; preserves compact local bindings, imports, and overload groups.
• require-safety-comment-for-type-assertion — requires each non-const assertion to have a nearby, non-empty invariant justification. Marker prefixes are configurable and default to SAFETY.

Effect rules

• no-manual-effect-error-tag — rejects manual _tag comparisons and switches inside broad Effect.catch, Effect.catchAll, and Effect.catchIf handlers in favor of tagged error handlers.
• no-manual-tag-comparison — rejects direct _tag comparisons and _tag switches in favor of Match, Predicate.isTagged, or tagged-enum matching.
• no-manual-tagged-construction — rejects literal _tag object construction in favor of Schema, tagged class/error, or Data.taggedEnum constructors. Match.when and Match.not patterns remain allowed.
• no-service-constructor-imports — rejects named make<CapabilityName> imports from relative project modules outside *.test.* and *.spec.* files. Runtime callers should import the owning Layer and yield the contextual service instead. Package and path-alias imports, default imports, and static constructors such as WorkspaceName.make are outside the rule.
• prefer-effect-match — rejects chained literal ternaries over the same value in favor of Effect's Match API.

Analysis boundaries

The rules use Oxlint's ESTree and lexical-scope APIs rather than a TypeScript type checker. They resolve same-file aliases—including block-scoped aliases, forward references, and transparent generic aliases—but do not infer imported type definitions or cross-file call signatures. Rules that inspect calls therefore document when enforcement is intentionally local.

Violation examples

Each snippet below is rejected by the named rule.

no-array-filter-map

const users: User[] = loadUsers();
const emails = users.filter(user => user.active).map(user => user.email);
const found = users.map(lookup).filter(value => value !== undefined);

Prefer lazy iterator helpers