eslint-plugin-zachs-rules

A small set of custom ESLint rules.

Rules

• zachs-rules/no-single-use-const

  • Reports const variables that are read exactly once and can often be inlined.
  • Skips exports, destructuring, declare const, and variables with non-initializer writes.
  • Set { ignoreConstantCase: true } to skip names like API_URL and VARS_LIKE_THIS.

• zachs-rules/prefer-object-spread-for-exact-object-map

  • Reports repeated same-name property maps when TypeScript proves the mapped keys exactly match the source object's known properties.
  • Recommendation: { ...deployment }.

• zachs-rules/prefer-pick-for-object-subset-map

  • Reports repeated same-name property maps when TypeScript proves the mapped keys are a subset of the source object's known properties, or the source has an index signature.
  • Recommendation: pick(deployment, ["createdAt", "id", "projectId", "status"]).

The object-map rules intentionally skip renamed properties, computed properties, already-spread objects, single-property mappings, unions, and unknown-like source types.

Usage

// eslint.config.ts
import zachsRules from "eslint-plugin-zachs-rules"
import parser from "@typescript-eslint/parser"

export default [
  {
    files: ["**/*.ts"],
    languageOptions: {
      parser,
      parserOptions: {
        projectService: true,
        tsconfigRootDir: import.meta.dirname,
      },
    },
    plugins: {
      "zachs-rules": zachsRules,
    },
    rules: {
      "zachs-rules/no-single-use-const": ["warn", { ignoreConstantCase: true }],
      "zachs-rules/prefer-object-spread-for-exact-object-map": "warn",
      "zachs-rules/prefer-pick-for-object-subset-map": "warn",
    },
  },
]

Development

bun install
bun run check

The package uses Bun, Prettier, oxlint with type-aware linting, and zshy for build output.