Export ConfigExtension type from package

src/index.ts

@@ -8,6 +8,7 @@ export { twMerge } from './lib/tw-merge'
 export {
     type ClassValidator,
     type Config,
+    type ConfigExtension,
     type DefaultClassGroupIds,
     type DefaultThemeGroupIds,
     type ExperimentalParseClassNameParam,

src/lib/class-group-utils.ts

@@ -1,28 +1,28 @@
 import {
+    AnyClassGroupIds,
+    AnyConfig,
+    AnyThemeGroupIds,
     ClassGroup,
     ClassValidator,
     Config,
-    GenericClassGroupIds,
-    GenericConfig,
-    GenericThemeGroupIds,
     ThemeGetter,
     ThemeObject,
 } from './types'
 
 export interface ClassPartObject {
     nextPart: Map<string, ClassPartObject>
     validators: ClassValidatorObject[]
-    classGroupId?: GenericClassGroupIds
+    classGroupId?: AnyClassGroupIds
 }
 
 interface ClassValidatorObject {
-    classGroupId: GenericClassGroupIds
+    classGroupId: AnyClassGroupIds
     validator: ClassValidator
 }
 
 const CLASS_PART_SEPARATOR = '-'
 
-export const createClassGroupUtils = (config: GenericConfig) => {
+export const createClassGroupUtils = (config: AnyConfig) => {
     const classMap = createClassMap(config)
     const { conflictingClassGroups, conflictingClassGroupModifiers } = config
 
@@ -38,7 +38,7 @@ export const createClassGroupUtils = (config: GenericConfig) => {
     }
 
     const getConflictingClassGroupIds = (
-        classGroupId: GenericClassGroupIds,
+        classGroupId: AnyClassGroupIds,
         hasPostfixModifier: boolean,
     ) => {
         const conflicts = conflictingClassGroups[classGroupId] || []
@@ -59,7 +59,7 @@ export const createClassGroupUtils = (config: GenericConfig) => {
 const getGroupRecursive = (
     classParts: string[],
     classPartObject: ClassPartObject,
-): GenericClassGroupIds | undefined => {
+): AnyClassGroupIds | undefined => {
     if (classParts.length === 0) {
         return classPartObject.classGroupId
     }
@@ -103,7 +103,7 @@ const getGroupIdForArbitraryProperty = (className: string) => {
 /**
  * Exported for testing only
  */
-export const createClassMap = (config: Config<GenericClassGroupIds, GenericThemeGroupIds>) => {
+export const createClassMap = (config: Config<AnyClassGroupIds, AnyThemeGroupIds>) => {
     const { theme, prefix } = config
     const classMap: ClassPartObject = {
         nextPart: new Map<string, ClassPartObject>(),
@@ -123,10 +123,10 @@ export const createClassMap = (config: Config<GenericClassGroupIds, GenericTheme
 }
 
 const processClassesRecursively = (
-    classGroup: ClassGroup<GenericThemeGroupIds>,
+    classGroup: ClassGroup<AnyThemeGroupIds>,
     classPartObject: ClassPartObject,
-    classGroupId: GenericClassGroupIds,
-    theme: ThemeObject<GenericThemeGroupIds>,
+    classGroupId: AnyClassGroupIds,
+    theme: ThemeObject<AnyThemeGroupIds>,
 ) => {
     classGroup.forEach((classDefinition) => {
         if (typeof classDefinition === 'string') {
@@ -187,9 +187,9 @@ const isThemeGetter = (func: ClassValidator | ThemeGetter): func is ThemeGetter
     (func as ThemeGetter).isThemeGetter
 
 const getPrefixedClassGroupEntries = (
-    classGroupEntries: Array<[classGroupId: string, classGroup: ClassGroup<GenericThemeGroupIds>]>,
+    classGroupEntries: Array<[classGroupId: string, classGroup: ClassGroup<AnyThemeGroupIds>]>,
     prefix: string | undefined,
-): Array<[classGroupId: string, classGroup: ClassGroup<GenericThemeGroupIds>]> => {
+): Array<[classGroupId: string, classGroup: ClassGroup<AnyThemeGroupIds>]> => {
     if (!prefix) {
         return classGroupEntries
     }

src/lib/config-utils.ts

@@ -1,11 +1,11 @@
 import { createClassGroupUtils } from './class-group-utils'
 import { createLruCache } from './lru-cache'
 import { createParseClassName } from './parse-class-name'
-import { GenericConfig } from './types'
+import { AnyConfig } from './types'
 
 export type ConfigUtils = ReturnType<typeof createConfigUtils>
 
-export const createConfigUtils = (config: GenericConfig) => ({
+export const createConfigUtils = (config: AnyConfig) => ({
     cache: createLruCache<string, string>(config.cacheSize),
     parseClassName: createParseClassName(config),
     ...createClassGroupUtils(config),

src/lib/create-tailwind-merge.ts

@@ -1,10 +1,10 @@
 import { createConfigUtils } from './config-utils'
 import { mergeClassList } from './merge-classlist'
 import { ClassNameValue, twJoin } from './tw-join'
-import { GenericConfig } from './types'
+import { AnyConfig } from './types'
 
-type CreateConfigFirst = () => GenericConfig
-type CreateConfigSubsequent = (config: GenericConfig) => GenericConfig
+type CreateConfigFirst = () => AnyConfig
+type CreateConfigSubsequent = (config: AnyConfig) => AnyConfig
 type TailwindMerge = (...classLists: ClassNameValue[]) => string
 type ConfigUtils = ReturnType<typeof createConfigUtils>
 
@@ -20,7 +20,7 @@ export function createTailwindMerge(
     function initTailwindMerge(classList: string) {
         const config = createConfigRest.reduce(
             (previousConfig, createConfigCurrent) => createConfigCurrent(previousConfig),
-            createConfigFirst() as GenericConfig,
+            createConfigFirst() as AnyConfig,
         )
 
         configUtils = createConfigUtils(config)

src/lib/extend-tailwind-merge.ts

@@ -1,9 +1,9 @@
 import { createTailwindMerge } from './create-tailwind-merge'
 import { getDefaultConfig } from './default-config'
 import { mergeConfigs } from './merge-configs'
-import { ConfigExtension, DefaultClassGroupIds, DefaultThemeGroupIds, GenericConfig } from './types'
+import { AnyConfig, ConfigExtension, DefaultClassGroupIds, DefaultThemeGroupIds } from './types'
 
-type CreateConfigSubsequent = (config: GenericConfig) => GenericConfig
+type CreateConfigSubsequent = (config: AnyConfig) => AnyConfig
 
 export const extendTailwindMerge = <
     AdditionalClassGroupIds extends string = never,

src/lib/merge-configs.ts

@@ -1,11 +1,11 @@
-import { ConfigExtension, GenericConfig } from './types'
+import { AnyConfig, ConfigExtension } from './types'
 
 /**
  * @param baseConfig Config where other config will be merged into. This object will be mutated.
  * @param configExtension Partial config to merge into the `baseConfig`.
  */
 export const mergeConfigs = <ClassGroupIds extends string, ThemeGroupIds extends string = never>(
-    baseConfig: GenericConfig,
+    baseConfig: AnyConfig,
     {
         cacheSize,
         prefix,

src/lib/parse-class-name.ts

@@ -1,8 +1,8 @@
-import { GenericConfig } from './types'
+import { AnyConfig } from './types'
 
 export const IMPORTANT_MODIFIER = '!'
 
-export const createParseClassName = (config: GenericConfig) => {
+export const createParseClassName = (config: AnyConfig) => {
     const { separator, experimentalParseClassName } = config
     const isSeparatorSingleCharacter = separator.length === 1
     const firstSeparatorCharacter = separator[0]

src/lib/types.ts

@@ -1,8 +1,14 @@
+/**
+ * Type the tailwind-merge configuration adheres to.
+ */
 export interface Config<ClassGroupIds extends string, ThemeGroupIds extends string>
-    extends ConfigStatic,
-        ConfigGroups<ClassGroupIds, ThemeGroupIds> {}
+    extends ConfigStaticPart,
+        ConfigGroupsPart<ClassGroupIds, ThemeGroupIds> {}
 
-interface ConfigStatic {
+/**
+ * The static part of the tailwind-merge configuration. When merging multiple configurations, the properties of this interface are always overridden.
+ */
+interface ConfigStaticPart {
     /**
      * Integer indicating size of LRU cache used for memoizing results.
      * - Cache might be up to twice as big as `cacheSize`
@@ -75,7 +81,10 @@ export interface ExperimentalParsedClassName {
     maybePostfixModifierPosition: number | undefined
 }
 
-interface ConfigGroups<ClassGroupIds extends string, ThemeGroupIds extends string> {
+/**
+ * The dynamic part of the tailwind-merge configuration. When merging multiple configurations, the user can choose to either override or extend the properties of this interface.
+ */
+interface ConfigGroupsPart<ClassGroupIds extends string, ThemeGroupIds extends string> {
     /**
      * Theme scales used in classGroups.
      * The keys are the same as in the Tailwind config but the values are sometimes defined more broadly.
@@ -109,10 +118,13 @@ interface ConfigGroups<ClassGroupIds extends string, ThemeGroupIds extends strin
     >
 }
 
+/**
+ * Type of the configuration object that can be passed to `extendTailwindMerge`.
+ */
 export interface ConfigExtension<ClassGroupIds extends string, ThemeGroupIds extends string>
-    extends Partial<ConfigStatic> {
-    override?: PartialPartial<ConfigGroups<ClassGroupIds, ThemeGroupIds>>
-    extend?: PartialPartial<ConfigGroups<ClassGroupIds, ThemeGroupIds>>
+    extends Partial<ConfigStaticPart> {
+    override?: PartialPartial<ConfigGroupsPart<ClassGroupIds, ThemeGroupIds>>
+    extend?: PartialPartial<ConfigGroupsPart<ClassGroupIds, ThemeGroupIds>>
 }
 
 type PartialPartial<T> = {
@@ -131,18 +143,24 @@ type ClassDefinition<ThemeGroupIds extends string> =
     | ClassObject<ThemeGroupIds>
 export type ClassValidator = (classPart: string) => boolean
 export interface ThemeGetter {
-    (theme: ThemeObject<GenericThemeGroupIds>): ClassGroup<GenericClassGroupIds>
+    (theme: ThemeObject<AnyThemeGroupIds>): ClassGroup<AnyClassGroupIds>
     isThemeGetter: true
 }
 type ClassObject<ThemeGroupIds extends string> = Record<
     string,
     readonly ClassDefinition<ThemeGroupIds>[]
 >
 
-// Hack from https://stackoverflow.com/questions/56687668/a-way-to-disable-type-argument-inference-in-generics/56688073#56688073
+/**
+ * Hack from https://stackoverflow.com/questions/56687668/a-way-to-disable-type-argument-inference-in-generics/56688073#56688073
+ *
+ * Could be replaced with NoInfer utility type from TypeScript (https://www.typescriptlang.org/docs/handbook/utility-types.html#noinfertype), but that is only supported in TypeScript 5.4 or higher, so I should wait some time before using it.
+ */
 export type NoInfer<T> = [T][T extends any ? 0 : never]
 
 /**
+ * Theme group IDs included in the default configuration of tailwind-merge.
+ *
  * If you want to use a scale that is not supported in the `ThemeObject` type,
  * consider using `classGroups` instead of `theme`.
  *
@@ -176,6 +194,9 @@ export type DefaultThemeGroupIds =
     | 'spacing'
     | 'translate'
 
+/**
+ * Class group IDs included in the default configuration of tailwind-merge.
+ */
 export type DefaultClassGroupIds =
     | 'accent'
     | 'align-content'
@@ -458,7 +479,10 @@ export type DefaultClassGroupIds =
     | 'will-change'
     | 'z'
 
-export type GenericClassGroupIds = string
-export type GenericThemeGroupIds = string
+export type AnyClassGroupIds = string
+export type AnyThemeGroupIds = string
 
-export type GenericConfig = Config<GenericClassGroupIds, GenericThemeGroupIds>
+/**
+ * type of the tailwind-merge configuration that allows for any possible configuration.
+ */
+export type AnyConfig = Config<AnyClassGroupIds, AnyThemeGroupIds>

tests/public-api.test.ts

@@ -4,6 +4,7 @@ import {
     ClassNameValue,
     ClassValidator,
     Config,
+    ConfigExtension,
     DefaultClassGroupIds,
     DefaultThemeGroupIds,
     createTailwindMerge,
@@ -183,7 +184,9 @@ test('mergeConfigs has correct inputs and outputs', () => {
 })
 
 test('extendTailwindMerge has correct inputs and outputs', () => {
-    expect(extendTailwindMerge({})).toStrictEqual(expect.any(Function))
+    expect(extendTailwindMerge({} satisfies ConfigExtension<string, string>)).toStrictEqual(
+        expect.any(Function),
+    )
 })
 
 test('fromTheme has correct inputs and outputs', () => {

tests/type-generics.test.ts

@@ -1,7 +1,7 @@
 import { expect, test } from 'vitest'
 
 import { extendTailwindMerge, fromTheme, getDefaultConfig, mergeConfigs } from '../src'
-import { GenericConfig } from '../src/lib/types'
+import { AnyConfig } from '../src/lib/types'
 
 test('extendTailwindMerge type generics work correctly', () => {
     const tailwindMerge1 = extendTailwindMerge({
@@ -69,7 +69,7 @@ test('extendTailwindMerge type generics work correctly', () => {
 
     expect(tailwindMerge2('')).toBe('')
 
-    const tailwindMerge3 = extendTailwindMerge((v: GenericConfig) => v, getDefaultConfig)
+    const tailwindMerge3 = extendTailwindMerge((v: AnyConfig) => v, getDefaultConfig)
 
     expect(tailwindMerge3('')).toBe('')
 })