No Implicit Boolean

Require explicit comparisons in conditions instead of relying on truthy/falsy coercion.

Summary

The no-implicit-boolean rule reports bare identifiers, member expressions, call expressions, and their negations (!value, !fn()) when used as conditions in if, while, do...while, for, and ternary statements. For logical expressions (&&, ||), each operand is checked independently.

Why Use This Rule?

1. Prevents subtle bugs from truthy/falsy coercion (e.g., 0, "", and null are all falsy).
2. Makes the developer's intent explicit (=== undefined, === true, > 0).
3. Keeps conditions self-documenting so readers understand what is actually being checked.

Examples

Correct

if (value !== undefined) {}

if (Array.isArray(x) === false) {}

if (a !== undefined && b === true) {}

while (items.length > 0) {}

// Ternary with explicit comparison — passes the check.
const label = (isDryRun === true) ? 'skip' : 'apply';

Incorrect

if (value) {}

if (!value) {}

while (items.length) {}

if (value && other) {}

Configuration

Enable the rule in your ESLint flat config:

import { noImplicitBoolean } from '@cbnventures/nova/rules/eslint';

export default [
  {
    plugins: {
      '@cbnventures/nova': {
        rules: {
          'no-implicit-boolean': noImplicitBoolean,
        },
      },
    },
    rules: {
      '@cbnventures/nova/no-implicit-boolean': ['warn'],
    },
  },
];

This rule has no additional options.

Troubleshooting

• Warning fires on !Array.isArray(x). — Use Array.isArray(x) === false instead. All negations of identifiers, member expressions, and call expressions are flagged.
• Warning fires on if (value && other). — Each operand in a logical expression is checked independently. Both value and other need explicit comparisons.
• Warning fires on a ternary condition. — Ternary conditions are checked the same as if conditions. Use an explicit comparison like (isDryRun === true) ? a : b.