prefer-type-fest-conditional-pick-deep

Require TypeFest ConditionalPickDeep<T, Condition, Options?> instead of legacy deep conditional-pick aliases.

Targeted pattern scope

This rule targets imported aliases that mirror deep conditional property filtering semantics (for example, PickDeepByTypes and PickDeepByType).

What this rule reports

Type references that resolve to imported deep conditional-pick aliases.

Why this rule exists

ConditionalPickDeep is the canonical TypeFest helper for recursively filtering object properties by value condition. Standardizing on this utility improves consistency and readability.

❌ Incorrect

import type { PickDeepByTypes } from "type-aliases";

type StringProps = PickDeepByTypes<User, string>;

✅ Correct

import type { ConditionalPickDeep } from "type-fest";

type StringProps = ConditionalPickDeep<User, string>;

Behavior and migration notes

ConditionalPickDeep<T, Condition, Options?> recursively selects keys whose values match Condition.
This rule only targets known alias names that represent the same intent.
Keep custom aliases only when they intentionally add behavior beyond deep conditional filtering.

Additional examples

❌ Incorrect — Additional example

import type { PickDeepByType } from "type-aliases";

type NumericProps = PickDeepByType<User, number>;

✅ Correct — Additional example

import type { ConditionalPickDeep } from "type-fest";

type NumericProps = ConditionalPickDeep<User, number>;

✅ Correct — Repository-wide usage

type DateProps = ConditionalPickDeep<User, Date>;

ESLint flat config example

import typefest from "eslint-plugin-typefest";

export default [
    {
        plugins: { typefest },
        rules: {
            "typefest/prefer-type-fest-conditional-pick-deep": "error",
        },
    },
];

When not to use it

Disable this rule if external API contracts require specific alias names.

Package documentation

TypeFest package documentation:

Source file: source/conditional-pick-deep.d.ts

/**
Pick keys recursively from the shape that matches the given condition.

@category Object
*/
export type ConditionalPickDeep<
    Type,
    Condition,
    Options extends ConditionalPickDeepOptions = {},
> = ...

Rule catalog ID: R082

prefer-type-fest-conditional-pick-deep

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