prefer-ts-extras-is-safe-integer

Prefer isSafeInteger from ts-extras over Number.isSafeInteger(...).

This keeps predicate usage consistent with other ts-extras narrowing helpers.

Targeted pattern scope

This rule focuses on direct Number.isSafeInteger(value) calls that can be migrated to isSafeInteger(value) with deterministic fixes.

Number.isSafeInteger(value) call sites that can use isSafeInteger(value).

Alias indirection, wrapper helpers, and non-canonical call shapes are excluded to keep isSafeInteger(value) migrations safe.

What this rule reports

This rule reports Number.isSafeInteger(value) call sites when isSafeInteger(value) is the intended replacement.

Number.isSafeInteger(value) call sites that can use isSafeInteger(value).

Why this rule exists

isSafeInteger standardizes safe-integer validation and keeps numeric guard usage consistent with other ts-extras helpers.

Safety-bound checks use one helper convention.
Predicate style is consistent with isInteger and isFinite.
Guard code for IDs/counters avoids mixed native/helper forms.

❌ Incorrect

const isSafe = Number.isSafeInteger(value);

✅ Correct

const isSafe = isSafeInteger(value);

Behavior and migration notes

Runtime behavior matches native Number.isSafeInteger.
Values outside Number.MIN_SAFE_INTEGER / Number.MAX_SAFE_INTEGER return false.
Non-number values are not coerced.

Additional examples

❌ Incorrect — Additional example

if (Number.isSafeInteger(quantity)) {
    persist(quantity);
}

✅ Correct — Additional example

if (isSafeInteger(quantity)) {
    persist(quantity);
}

✅ Correct — Repository-wide usage

const supported = isSafeInteger(index);

ESLint flat config example

import typefest from "eslint-plugin-typefest";

export default [
    {
        plugins: { typefest },
        rules: {
            "typefest/prefer-ts-extras-is-safe-integer": "error",
        },
    },
];

When not to use it

Disable this rule if your team enforces native Number.isSafeInteger calls.

Package documentation

ts-extras package documentation:

Source file: source/is-safe-integer.ts

/**
A strongly-typed version of `Number.isSafeInteger()`.

@category Improved builtin
@category Type guard
*/

Rule catalog ID: R023

prefer-ts-extras-is-safe-integer

Targeted pattern scope

What this rule reports

Why this rule exists

❌ Incorrect

✅ Correct

Behavior and migration notes

Additional examples

❌ Incorrect — Additional example

✅ Correct — Additional example

✅ Correct — Repository-wide usage

ESLint flat config example

When not to use it

Package documentation

Further reading

Adoption resources

Targeted pattern scope​

What this rule reports​

Why this rule exists​

❌ Incorrect​

✅ Correct​

Behavior and migration notes​

Additional examples​

❌ Incorrect — Additional example​

✅ Correct — Additional example​

✅ Correct — Repository-wide usage​

ESLint flat config example​

When not to use it​

Package documentation​

Further reading​

Adoption resources​

Targeted pattern scope

What this rule reports

Why this rule exists

❌ Incorrect

✅ Correct

Behavior and migration notes

Additional examples

❌ Incorrect — Additional example

✅ Correct — Additional example

✅ Correct — Repository-wide usage

ESLint flat config example

When not to use it

Package documentation

Further reading

Adoption resources