mergeConfig()

mergeConfig() calls mergeConfig from vitest/config and types the result as base & overrides.

Signature

import { mergeConfig } from '@repobuddy/vitest/config/node'

function mergeConfig<D extends Record<string, any>, O extends Record<string, any> | undefined>(
  base: D,
  overrides: O,
  isRoot?: boolean | undefined,
): D & O

It is also exported from @repobuddy/vitest/config/browser and @repobuddy/vitest/config.

Arguments

Argument	Type	Default	Effect
`base`	object	required	The config to start from
`overrides`	object or `undefined`	required	The config merged on top. Its values win.
`isRoot`	`boolean`	`true` (Vite’s default)	Passed to Vite’s `mergeConfig`. Leave it unset when you merge whole configs.

Output

A new object. Neither argument is changed.

Behavior

Arrays are concatenated: base items first, then overrides items.
Objects are merged key by key.
Other values from overrides replace values in base.
null and undefined values in overrides are skipped, so they do not clear a base value.
Passing undefined as overrides returns a copy of base.
Passing a function config throws Cannot merge config in form of callback.

Examples

mergeConfig(
  { test: { name: 'base', include: ['a'], testTimeout: 1 } },
  { test: { include: ['b'], testTimeout: 2 } },
)
// { test: { name: 'base', include: ['a', 'b'], testTimeout: 2 } }

Extend a shared config in a package:

import { defineConfig } from 'vitest/config'
import { mergeConfig } from '@repobuddy/vitest/config/node'
import shared from '../../vitest.shared.ts'

export default mergeConfig(shared, defineConfig({ test: { name: 'my-package' } }))