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no-conditional-statement

Disallow if and switch statements.

Targeted pattern scope​

This rule targets IfStatement and SwitchStatement nodes.

What this rule reports​

  • Any if statement (or branch completeness issues when configured)
  • Any switch statement (or case completeness issues when configured)

Why this rule exists​

Expression-oriented branching is easier to compose and test in immutable-style codebases.

❌ Incorrect​

if (enabled) {
  return a;
}
return b;

βœ… Correct​

return enabled ? a : b;

Additional examples​

// ❌ Switch statement branching
switch (status) {
  case "idle":
    return "Ready";
  case "loading":
    return "Loading…";
  default:
    return "Done";
}

// βœ… Lookup table expression
const labels = {
  done: "Done",
  idle: "Ready",
  loading: "Loading…",
} as const;

return labels[status] ?? "Done";

ESLint flat config example​

import immutable from "eslint-plugin-immutable-2";

export default [
  {
    files: ["**/*.{js,mjs,cjs,ts,mts,cts,tsx}"],
    plugins: { immutable },
    rules: {
      "immutable/no-conditional-statement": "error",
    },
  },
];

When not to use it​

If your team favors explicit if/switch statements for readability (especially in long business workflows), enforcing expression-only branching can hurt clarity. In those modules, prefer keeping conventional branching and use other immutability rules to guard mutation.

Rule catalog ID: R903

Further reading​