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Add RemovePrefix type (#1194)
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‎index.d.ts‎

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@@ -181,6 +181,7 @@ export type {Get} from './source/get.d.ts';
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export type {LastArrayElement} from './source/last-array-element.d.ts';
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export type {ConditionalSimplify} from './source/conditional-simplify.d.ts';
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export type {ConditionalSimplifyDeep} from './source/conditional-simplify-deep.d.ts';
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export type {RemovePrefix} from './source/remove-prefix.d.ts';
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// Miscellaneous
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export type {GlobalThis} from './source/global-this.d.ts';

‎readme.md‎

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@@ -233,6 +233,7 @@ Click the type names for complete docs.
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- [`Replace`](source/replace.d.ts) - Represents a string with some or all matches replaced by a replacement.
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- [`StringSlice`](source/string-slice.d.ts) - Returns a string slice of a given range, just like `String#slice()`.
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- [`StringRepeat`](source/string-repeat.d.ts) - Returns a new string which contains the specified number of copies of a given string, just like `String#repeat()`.
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- [`RemovePrefix`](source/remove-prefix.d.ts) - Removes the specified prefix from the start of a string.
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### Array
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‎source/delimiter-case.d.ts‎

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import type {ApplyDefaultOptions, AsciiPunctuation, StartsWith} from './internal/index.d.ts';
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import type {IsStringLiteral} from './is-literal.d.ts';
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import type {Merge} from './merge.d.ts';
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import type {RemovePrefix} from './remove-prefix.d.ts';
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import type {DefaultWordsOptions, Words, WordsOptions} from './words.d.ts';
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export type DefaultDelimiterCaseOptions = Merge<DefaultWordsOptions, {splitOnNumbers: false}>;
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}${FirstWord}`>
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: OutputString;
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type RemoveFirstLetter<S extends string> = S extends `${infer _}${infer Rest}`
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? Rest
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: '';
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/**
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Convert a string literal to a custom string delimiter casing.
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@@ -71,8 +68,8 @@ export type DelimiterCase<
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> = Value extends string
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? IsStringLiteral<Value> extends false
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? Value
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: Lowercase<RemoveFirstLetter<DelimiterCaseFromArray<
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: Lowercase<RemovePrefix<DelimiterCaseFromArray<
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Words<Value, ApplyDefaultOptions<WordsOptions, DefaultDelimiterCaseOptions, Options>>,
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Delimiter
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>>>
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>, string, {strict: false}>>
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: Value;

‎source/remove-prefix.d.ts‎

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import type {ApplyDefaultOptions} from './internal/object.d.ts';
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import type {IfNotAnyOrNever, Not} from './internal/type.d.ts';
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import type {IsStringLiteral} from './is-literal.d.ts';
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import type {Or} from './or.d.ts';
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/**
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@see {@link RemovePrefix}
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*/
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type RemovePrefixOptions = {
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/**
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When enabled, instantiations with non-literal prefixes (e.g., `string`, `Uppercase<string>`, `` `on${string}` ``) simply return `string`, since their precise structure cannot be statically determined.
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Note: Disabling this option can produce misleading results that might not reflect the actual runtime behavior.
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For example, ``RemovePrefix<'on-change', `${string}-`, {strict: false}>`` returns `'change'`, but at runtime, prefix could be `'handle-'` (which satisfies `` `${string}-` ``) and removing `'handle-'` from `'on-change'` would not result in `'change'`.
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So, it is recommended to not disable this option unless you are aware of the implications.
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@default true
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@example
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```
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type A = RemovePrefix<'on-change', `${string}-`, {strict: true}>;
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//=> string
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type B = RemovePrefix<'on-change', `${string}-`, {strict: false}>;
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//=> 'change'
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type C = RemovePrefix<'on-change', string, {strict: true}>;
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//=> string
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type D = RemovePrefix<'on-change', string, {strict: false}>;
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//=> 'n-change'
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type E = RemovePrefix<`${string}/${number}`, `${string}/`, {strict: true}>;
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//=> string
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type F = RemovePrefix<`${string}/${number}`, `${string}/`, {strict: false}>;
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//=> `${number}`
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```
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Note: This option has no effect when only the input string type is non-literal. For example, ``RemovePrefix<`on-${string}`, 'on-'>`` will always return `string`.
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@example
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```
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import type {RemovePrefix} from 'type-fest';
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type A = RemovePrefix<`on-${string}`, 'on-', {strict: true}>;
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//=> string
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type B = RemovePrefix<`on-${string}`, 'on-', {strict: false}>;
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//=> string
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type C = RemovePrefix<`id-${number}`, 'id-', {strict: true}>;
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//=> `${number}`
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type D = RemovePrefix<`id-${number}`, 'id-', {strict: false}>;
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//=> `${number}`
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```
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Note: If it can be statically determined that the input string can never start with the specified non-literal prefix, then the input string is returned as-is, regardless of the value of this option.
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For example, ``RemovePrefix<`${string}/${number}`, `${string}:`>`` returns `` `${string}/${number}` ``, since a string of type `` `${string}/${number}` `` can never start with a prefix of type `` `${string}:` ``.
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```
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import type {RemovePrefix} from 'type-fest';
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type A = RemovePrefix<`${string}/${number}`, `${string}:`, {strict: true}>;
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//=> `${string}/${number}`
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type B = RemovePrefix<`${string}/${number}`, `${string}:`, {strict: false}>;
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//=> `${string}/${number}`
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type C = RemovePrefix<'on-change', `${number}-`, {strict: true}>;
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//=> 'on-change'
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type D = RemovePrefix<'on-change', `${number}-`, {strict: false}>;
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//=> 'on-change'
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```
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*/
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strict?: boolean;
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};
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type DefaultRemovePrefixOptions = {
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strict: true;
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};
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/**
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Removes the specified prefix from the start of a string.
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@example
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```
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import type {RemovePrefix} from 'type-fest';
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type A = RemovePrefix<'on-change', 'on-'>;
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//=> 'change'
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type B = RemovePrefix<'sm:flex' | 'sm:p-4' | 'sm:gap-2', 'sm:'>;
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//=> 'flex' | 'p-4' | 'gap-2'
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type C = RemovePrefix<'on-change', 'off-'>;
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//=> 'on-change'
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type D = RemovePrefix<`handle${Capitalize<string>}`, 'handle'>;
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//=> Capitalize<string>
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```
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@see {@link RemovePrefixOptions}
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@category String
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@category Template literal
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*/
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export type RemovePrefix<S extends string, Prefix extends string, Options extends RemovePrefixOptions = {}> =
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IfNotAnyOrNever<
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S,
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IfNotAnyOrNever<
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Prefix,
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_RemovePrefix<S, Prefix, ApplyDefaultOptions<RemovePrefixOptions, DefaultRemovePrefixOptions, Options>>,
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string,
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S
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>
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>;
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type _RemovePrefix<S extends string, Prefix extends string, Options extends Required<RemovePrefixOptions>> =
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Prefix extends string // For distributing `Prefix`
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? S extends `${Prefix}${infer Rest}`
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? Or<IsStringLiteral<Prefix>, Not<Options['strict']>> extends true
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? Rest
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: string // Fallback to `string` when `Prefix` is non-literal and `strict` is disabled
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: S // Return back `S` when `Prefix` is not present at the start of `S`
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: never;

‎test-d/remove-prefix.ts‎

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import {expectType} from 'tsd';
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import type {RemovePrefix} from '../source/remove-prefix.d.ts';
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expectType<'change'>({} as RemovePrefix<'on-change', 'on-'>);
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expectType<'Click'>({} as RemovePrefix<'handleClick', 'handle'>);
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expectType<'vscode'>({} as RemovePrefix<'.vscode', '.'>);
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expectType<'whitespace'>({} as RemovePrefix<' whitespace', ' '>);
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// Prefix not present
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expectType<''>({} as RemovePrefix<'', 'foo'>);
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expectType<'on-mouse-move'>({} as RemovePrefix<'on-mouse-move', 'click'>);
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// Empty prefix
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expectType<'baz'>({} as RemovePrefix<'baz', ''>);
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// Prefix completely matches the input string
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expectType<''>({} as RemovePrefix<'click', 'click'>);
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// Prefix partially matches the input string
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expectType<'foobar'>({} as RemovePrefix<'foobar', 'foobaz'>);
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expectType<'hello'>({} as RemovePrefix<'hello', 'helloworld'>);
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// Multiple occurrences of prefix (should only remove from start)
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expectType<'bar-bar-foo'>({} as RemovePrefix<'bar-bar-bar-foo', 'bar-'>);
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expectType<'foofoo'>({} as RemovePrefix<'foofoofoo', 'foo'>);
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// === Non-literals ===
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// Input: Non-literal, Prefix: Literal
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expectType<string>({} as RemovePrefix<`hover:${string}`, 'hover:'>);
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expectType<Capitalize<string>>({} as RemovePrefix<`on${Capitalize<string>}`, 'on'>);
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expectType<`${number}`>({} as RemovePrefix<`id-${number}`, 'id-'>);
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expectType<`${string}--`>({} as RemovePrefix<`--${string}--`, '--'>);
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expectType<`focus:${string}`>({} as RemovePrefix<`hover:focus:${string}`, 'hover:'>);
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expectType<`user_${string}`>({} as RemovePrefix<`user_${string}`, 'admin_'>);
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expectType<string>({} as RemovePrefix<string, 'on'>);
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expectType<`${string}/${number}`>({} as RemovePrefix<`${string}/${number}`, 'foo'>);
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// Input: Literal, Prefix: Non-literal
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expectType<string>({} as RemovePrefix<'on-click', `${string}-`>);
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expectType<string>({} as RemovePrefix<'hover:flex', string>);
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expectType<'handle-click'>({} as RemovePrefix<'handle-click', Uppercase<string>>);
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expectType<'on-change'>({} as RemovePrefix<'on-change', `${string}--`>);
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// Input: Non-literal, Prefix: Non-literal
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expectType<string>({} as RemovePrefix<`hover:${string}`, `${string}:`>);
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expectType<string>({} as RemovePrefix<`${string}/${number}`, `${string}/`>);
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expectType<string>({} as RemovePrefix<string, string>);
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expectType<`${string}/${number}`>({} as RemovePrefix<`${string}/${number}`, `${string}:`>);
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expectType<`${number}:${number}`>({} as RemovePrefix<`${number}:${number}`, `-${string}`>);
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// Unions
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expectType<'click' | 'hover' | 'change'>({} as RemovePrefix<'on-click' | 'on-hover' | 'on-change', 'on-'>);
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expectType<'click' | 'hover' | 'handle-change'>({} as RemovePrefix<'on-click' | 'on-hover' | 'handle-change', 'on-'>);
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expectType<Uppercase<string> | `${number}`>({} as RemovePrefix<`id-${Uppercase<string>}` | `id-${number}`, 'id-'>);
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expectType<string>({} as RemovePrefix<`hover:${string}` | `focus:${string}`, `${string}:`>);
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expectType<'-change' | 'change'>({} as RemovePrefix<'on-change', 'on' | 'on-'>);
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expectType<'change' | 'on-change'>({} as RemovePrefix<'on-change', 'on-' | 'handle-'>);
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expectType<'on-change'>({} as RemovePrefix<'on-change', 'off-' | 'handle-'>);
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expectType<string>({} as RemovePrefix<'on-change', `${string}-` | 'on'>);
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expectType<'on:change' | 'onChange'>({} as RemovePrefix<'on:change' | 'onChange', `${string}-`>);
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expectType<'name' | 'get-name' | 'age' | 'set-age' | 'other'>(
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{} as RemovePrefix<'get-name' | 'set-age' | 'other', 'get-' | 'set-'>,
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);
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expectType<string>({} as RemovePrefix<`id:${Uppercase<string>}` | `id/${number}`, `${string}:` | `${string}/`>);
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// Boundary types
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expectType<any>({} as RemovePrefix<any, 'foo'>);
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expectType<never>({} as RemovePrefix<never, 'foo'>);
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expectType<string>({} as RemovePrefix<'on-change', any>);
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expectType<'on-change'>({} as RemovePrefix<'on-change', never>);
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// === strict: false ===
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// No effect if `Prefix` is a literal
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expectType<'change'>({} as RemovePrefix<'on-change', 'on-', {strict: false}>);
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expectType<'change' | 'hover'>({} as RemovePrefix<'on-change' | 'on-hover', 'on-', {strict: false}>);
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expectType<Capitalize<string>>({} as RemovePrefix<`handle${Capitalize<string>}`, 'handle', {strict: false}>);
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expectType<'click'>({} as RemovePrefix<'on-click', `${string}-`, {strict: false}>);
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expectType<'over:flex'>({} as RemovePrefix<'hover:flex', string, {strict: false}>);
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expectType<`${number}`>({} as RemovePrefix<`${string}/${number}`, `${string}/`, {strict: false}>);
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expectType<'change' | '-change'>({} as RemovePrefix<'on-change', `${string}-` | 'on', {strict: false}>);
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expectType<'on:change' | 'change'>({} as RemovePrefix<'on:change' | 'on-change', `${string}-`, {strict: false}>);
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expectType<Uppercase<string> | `id:${Uppercase<string>}` | `${number}` | `id/${number}`>(
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{} as RemovePrefix<`id:${Uppercase<string>}` | `id/${number}`, `${string}:` | `${string}/`, {strict: false}>,
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);
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// Generic assignability test
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type Assignability<S extends string> = S;
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// Output of `RemovePrefix` should be assignable to `string`.
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type Test1<S extends string, Prefix extends string> = Assignability<RemovePrefix<S, Prefix>>;
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type Test2<S extends Uppercase<string>, Prefix extends '-' | '/' | '#'> = Assignability<RemovePrefix<S, Prefix>>;

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