v5.0.5

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Bug fixes

The P module was mistakenly exposing some pattern methods that were intended to be namespaced by type. This release fixes this problem.

If you happened to use on of those following methods, here is where to find them now:

- P.between
+ P.number.between

- P.lt
+ P.number.lt

- P.gt
+ P.number.gt

- P.lte
+ P.number.lte

- P.gte
+ P.number.gte

- P.int
+ P.number.int

- P.finite
+ P.number.finite

- P.positive
+ P.number.positive

- P.negative
+ P.number.negative

- P.betweenBigInt
+ P.bigint.between

- P.ltBigInt
+ P.bigint.lt

- P.gtBigInt
+ P.bigint.gt

- P.lteBigInt
+ P.bigint.lte

- P.gteBigInt
+ P.bigint.gte

- P.positiveBigInt
+ P.bigint.positive

- P.negativeBigInt
+ P.bigint.negative

v5.0.4

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What's Changed

• 🐛 fix: Accept branded primitive types as patterns by @​gvergnaud in https://github.com/gvergnaud/ts-pattern/pull/180

Full Changelog: gvergnaud/ts-pattern@v5.0.3...v5.0.4

v5.0.3

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What's Changed

• 🐛 fix: Allow re-exporting patterns from ES Modules by @​gvergnaud in https://github.com/gvergnaud/ts-pattern/pull/175

Full Changelog: gvergnaud/ts-pattern@v5.0.2...v5.0.3

v5.0.2

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What's Changed

• fix(P.infer): Fix inference of arrays containing tuples in gvergnaud/ts-pattern@c52af6a
• refactoring: simplify selection types in gvergnaud/ts-pattern@1b7a36b
• perf: runtime perf improvement in .with in gvergnaud/ts-pattern@9b27384
• fix: use Symbol.for to make sure two concurrent versions of ts-pattern are compatible with one-another in gvergnaud/ts-pattern@d6d2e23
• docs: fix typo by @​juicyjusung in https://github.com/gvergnaud/ts-pattern/pull/170

New Contributors

• @​juicyjusung made their first contribution in https://github.com/gvergnaud/ts-pattern/pull/170

Full Changelog: gvergnaud/ts-pattern@v5.0.0...v5.0.2

v5.0.1

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v5.0.0: ❤️

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TS-Pattern v5 is finally out ❤️

Breaking changes

.with is now evaluated eagerly

In the previous version of TS-Pattern, no code would execute until you called .exhaustive() or .otherwise(...). For example, in the following code block, nothing would be logged to the console or thrown:

// TS-Pattern v4
type Input = { type: 'ok'; value: number } | { type: 'error'; error: Error };

// We don't call `.exhaustive`, so handlers don't run.
function someFunction(input: Input) {
  match(input)
    .with({ type: 'ok' }, ({ value }) => {
      console.log(value);
    })
    .with({ type: 'error' }, ({ error }) => {
      throw error;
    });
}

someFunction({ type: 'ok', value: 42 }); // nothing happens

In TS-Pattern v5, however, the library will execute the matching handler as soon as it finds it:

// TS-Pattern v5
someFunction({ type: 'ok', value: 42 }); // logs "42" to the console!

Handlers are now evaluated eagerly instead of lazily. In practice, this shouldn't change anything as long as you always finish your pattern matching expressions by either .exhaustive or .otherwise.

Matching on Maps and Sets

Matching Set and Map instances using .with(new Set(...)) and .with(new Map(...)) is no longer supported. If you want to match specific sets and maps, you should now use the P.map(keyPattern, valuePattern) and P.set(valuePattern) patterns:

- import { match } from 'ts-pattern';
+ import { match, P } from 'ts-pattern';

const someFunction = (value: Set<number> | Map<string, number>) =>
  match(value)
-   .with(new Set([P.number]), (set) => `a set of numbers`)
-   .with(new Map([['key', P.number]]), (map) => `map.get('key') is a number`)
+   .with(P.set(P.number), (set) => `a set of numbers`)
+   .with(P.map('key', P.number), (map) => `map.get('key') is a number`)
    .otherwise(() => null);

• The subpattern we provide in P.set(subpattern) should match all values in the set.
• The value subpattern we provide in P.map(keyPattern, subpattern) should only match the values matching keyPattern for the whole P.map(..) pattern to match the input.

New features

chainable methods

TS-Pattern v5's major addition is the ability to chain methods to narrow down the values matched by primitive patterns, like P.string or P.number.

Since a few examples is worth a thousand words, here are a few ways you can use chainable methods:

P.number methods

const example = (position: { x: number; y: number }) =>
  match(position)
    .with({ x: P.number.gte(100) }, (value) => '🎮')
    .with({ x: P.number.between(0, 100) }, (value) => '🎮')
    .with(
      {
        x: P.number.positive().int(),
        y: P.number.positive().int(),
      },
      (value) => '🎮'
    )
    .otherwise(() => 'x or y is negative');

Here is the full list of number methods:

• P.number.between(min, max): matches numbers between min and max.
• P.number.lt(max): matches numbers smaller than max.
• P.number.gt(min): matches numbers greater than min.
• P.number.lte(max): matches numbers smaller than or equal to max.
• P.number.gte(min): matches numbers greater than or equal to min.
• P.number.int(): matches integers.
• P.number.finite(): matches all numbers except Infinity and -Infinity
• P.number.positive(): matches positive numbers.
• P.number.negative(): matches negative numbers.

P.string methods

const example = (query: string) =>
  match(query)
    .with(P.string.startsWith('SELECT'), (query) => `selection`)
    .with(P.string.endsWith('FROM user'), (query) => `👯‍♂️`)
    .with(P.string.includes('*'), () => 'contains a star')
    // Methods can be chained:
    .with(P.string.startsWith('SET').includes('*'), (query) => `🤯`)
    .exhaustive();

Here is the full list of string methods:

• P.string.startsWith(str): matches strings that start with str.
• P.string.endsWith(str): matches strings that end with str.
• P.string.minLength(min): matches strings with at least min characters.
• P.string.maxLength(max): matches strings with at most max characters.
• P.string.includes(str): matches strings that contain str.
• P.string.regex(RegExp): matches strings if they match this regular expression.

Global methods

Some methods are available for all primitive type patterns:

• P.{..}.optional(): matches even if this property isn't present on the input object.
• P.{..}.select(): injects the matched value into the handler function.
• P.{..}.and(pattern): matches if the current pattern and the provided pattern match.
• P.{..}.or(pattern): matches if either the current pattern or the provided pattern match.

const example = (value: unknown) =>
  match(value)
    .with(
      {
        username: P.string,
        displayName: P.string.optional(),
      },
      () => `{ username:string, displayName?: string }`
    )
    .with(
      {
        title: P.string,
        author: { username: P.string.select() },
      },
      (username) => `author.username is ${username}`
    )
    .with(
      P.instanceOf(Error).and({ source: P.string }),
      () => `Error & { source: string }`
    )
    .with(P.string.or(P.number), () => `string | number`)
    .otherwise(() => null);

Variadic tuple patterns

With TS-Pattern, you are now able to create array (or more accurately tuple) pattern with a variable number of elements:

const example = (value: unknown) =>
  match(value)
    .with(
      // non-empty list of strings
      [P.string, ...P.array(P.string)],
      (value) => `value: [string, ...string[]]`
    )
    .otherwise(() => null);

Array patterns that include a ...P.array are called variadic tuple patterns. You may only have a single ...P.array, but as many fixed-index patterns as you want:

const example = (value: unknown) =>
  match(value)
    .with(
      [P.string, P.string, P.string, ...P.array(P.string)],
      (value) => `value: [string, string, string, ...string[]]`
    )
    .with(
      [P.string, P.string, ...P.array(P.string)],
      (value) => `value: [string, string, ...string[]]`
    )
    .with([], (value) => `value: []`)
    .otherwise(() => null);

Fixed-index patterns can also be set after the ...P.array variadic, or on both sides!

const example = (value: unknown) =>
  match(value)
    .with(
      [...P.array(P.number), P.string, P.number],
      (value) => `value: [...number[], string, number]`
    )
    .with(
      [P.boolean, ...P.array(P.string), P.number, P.symbol],
      (value) => `value: [boolean, ...string[], number, symbol]`
    )
    .otherwise(() => null);

Lastly, argument of P.array is now optional, and will default to P._, which matches anything:

const example = (value: unknown) =>
  match(value)
    //                         👇
    .with([P.string, ...P.array()], (value) => `value: [string, ...unknown[]]`)
    .otherwise(() => null);

.returnType

In TS-Pattern v4, the only way to explicitly set the return type of your match expression is to set the two <Input, Output> type parameters of match:

// TS-Pattern v4
match<
  { isAdmin: boolean; plan: 'free' | 'paid' }, // input type
  number // return type
>({ isAdmin, plan })
  .with({ isAdmin: true }, () => 123)
  .with({ plan: 'free' }, () => 'Oops!');
//                              ~~~~~~ ❌ not a number.

the main drawback is that you need to set the input type explicitly too, even though TypeScript should be able to infer it.

In TS-Pattern v5, you can use the .returnType<Type>() method to only set the return type:

match({ isAdmin, plan })
  .returnType<number>() // 👈 new
  .with({ isAdmin: true }, () => 123)
  .with({ plan: 'free' }, () => 'Oops!');
//                              ~~~~~~ ❌ not a number.

What's Changed

• TS-Pattern v5 base branch by @​gvergnaud in https://github.com/gvergnaud/ts-pattern/pull/139

Full Changelog: gvergnaud/ts-pattern@v4.3.0...v5.0.0

v4.3.0

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TS-Pattern and node16

TS-Pattern now fully supports moduleResolution: node16, with both ES and CommonJS modules. This resolves the long standing issue number #​110. Special thanks to @​Andarist and @​frankie303 for helping me understand and fix this issue ❤️

What's Changed

• build: better support moduleResolution: bundler by @​gvergnaud in https://github.com/gvergnaud/ts-pattern/pull/158
• Gvergnaud/fix build for nodenext and commonjs by @​gvergnaud in https://github.com/gvergnaud/ts-pattern/pull/160

Full Changelog: gvergnaud/ts-pattern@v4.2.2...v4.3.0

v4.2.3

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