> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/supermacro/neverthrow/llms.txt
> Use this file to discover all available pages before exploring further.

# Changelog

> Version history and release notes for NeverThrow

## Changelog

A comprehensive history of changes, improvements, and bug fixes in NeverThrow.

## v8.2.0 (Current)

### Minor Changes

<Accordion title="Add orTee method for error track side effects">
  **Pull Request:** [#615](https://github.com/supermacro/neverthrow/pull/615)\
  **Contributor:** [@konker](https://github.com/konker)

  Added `orTee`, which is the equivalent of `andTee` but for the error track. This method allows you to perform side effects on error values without affecting the Result's error type.

  **Example:**

  ```typescript theme={null}
  import { parseUserInput } from 'imaginary-parser'
  import { logParseError } from 'imaginary-logger'
  import { insertUser } from 'imaginary-database'

  const resAsync = parseUserInput(userInput)
    .orTee(logParseError)  // Log errors without affecting the Result
    .asyncAndThen(insertUser)

  // Note: No LogError appears in the Result type
  ```
</Accordion>

<Accordion title="Allow void arguments in ok/err/okAsync/errAsync">
  **Pull Request:** [#584](https://github.com/supermacro/neverthrow/pull/584)\
  **Contributor:** [@macksal](https://github.com/macksal)

  The `ok`, `err`, `okAsync`, and `errAsync` functions now accept zero arguments when returning `void`.

  **Example:**

  ```typescript theme={null}
  // Now valid:
  const result: Result<void, never> = ok()
  const error: Result<never, void> = err()
  const asyncResult: ResultAsync<void, never> = okAsync()
  const asyncError: ResultAsync<never, void> = errAsync()
  ```
</Accordion>

***

## v8.1.1

### Patch Changes

<Accordion title="Documentation updates for safeTry">
  **Pull Request:** [#600](https://github.com/supermacro/neverthrow/pull/600)\
  **Contributor:** [@m-shaka](https://github.com/m-shaka)

  Updated README.md documentation about `safeTry` and added `@deprecated` tag to `safeUnwrap`.
</Accordion>

***

## v8.1.0

### Minor Changes

<Accordion title="safeTry no longer requires safeUnwrap">
  **Pull Request:** [#589](https://github.com/supermacro/neverthrow/pull/589)\
  **Contributor:** [@dmmulroy](https://github.com/dmmulroy)

  `safeTry` no longer requires calling `.safeUnwrap()` on Results within the generator function. You can now use `yield*` directly on Result values.

  **Before:**

  ```typescript theme={null}
  function myFunc(): Result<number, string> {
    return safeTry<number, string>(function*() {
      const value = yield* mayFail().safeUnwrap()  // Had to call safeUnwrap
      return ok(value * 2)
    })
  }
  ```

  **After:**

  ```typescript theme={null}
  function myFunc(): ResultAsync<number, string> {
    return safeTry<number, string>(function*() {
      const value = yield* mayFail()  // No safeUnwrap needed
      return ok(value * 2)
    })
  }
  ```
</Accordion>

***

## v8.0.0

### Major Changes

<Accordion title="Breaking: orElse type argument order changed">
  **Pull Request:** [#484](https://github.com/supermacro/neverthrow/pull/484)\
  **Contributor:** [@braxtonhall](https://github.com/braxtonhall)

  The `orElse` method now allows changing ok types, making the types match the implementation.

  **Breaking Change:**

  The ok type must now be provided before the err type when explicitly providing type arguments.

  ```diff theme={null}
  - result.orElse<ErrType>(foo)
  + result.orElse<OkType, ErrType>(foo)
  ```

  **Migration:**

  This only applies if type arguments were explicitly provided at an `orElse` callsite. If the type arguments were inferred, no updates are needed during the upgrade.
</Accordion>

***

## v7.2.0

### Minor Changes

<Accordion title="safeTry returns ResultAsync for better composability">
  **Pull Request:** [#562](https://github.com/supermacro/neverthrow/pull/562)\
  **Contributor:** [@sharno](https://github.com/sharno)

  Changed the return type of `safeTry` from `Promise<Result<T, E>>` to `ResultAsync<T, E>` for better composability.

  **What This Means:**

  `ResultAsync` is thenable and behaves like a native Promise, but provides additional methods like `map`, `andThen`, and `mapErr` without needing to `await` or `.then()` first.

  **Example:**

  ```typescript theme={null}
  // Now you can chain directly
  safeTry(async function* () {
    // ...
  })
    .map(x => x * 2)
    .andThen(processValue)
    .match(
      (value) => console.log(value),
      (error) => console.error(error)
    )
  ```
</Accordion>

***

## v7.1.0

### Minor Changes

<Accordion title="Add andTee and andThrough for side effects">
  **Pull Request:** [#467](https://github.com/supermacro/neverthrow/pull/467)\
  **Contributor:** [@untidy-hair](https://github.com/untidy-hair)

  Added `andTee` and `andThrough` methods to handle side effects:

  * **`andTee`**: Perform side effects without affecting the Result type (errors are ignored)
  * **`andThrough`**: Validate or perform checks where errors should propagate

  **Example:**

  ```typescript theme={null}
  // andTee for logging (errors ignored)
  parseUserInput(userInput)
    .andTee(logUser)
    .asyncAndThen(insertUser)

  // andThrough for validation (errors propagated)
  parseUserInput(userInput)
    .andThrough(validateUser)
    .asyncAndThen(insertUser)
  ```
</Accordion>

### Patch Changes

<Accordion title="Fix combineWithAllErrors types">
  **Pull Request:** [#483](https://github.com/supermacro/neverthrow/pull/483)\
  **Contributor:** [@braxtonhall](https://github.com/braxtonhall)

  Fixed type definitions for `combineWithAllErrors` to properly handle error arrays.
</Accordion>

<Accordion title="Improve err() string inference">
  **Pull Request:** [#563](https://github.com/supermacro/neverthrow/pull/563)\
  **Contributor:** [@mattpocock](https://github.com/mattpocock)

  Made `err()` infer strings narrowly for easier error tagging.

  **Example:**

  ```typescript theme={null}
  // Error type is inferred as 'NotFound' (not generic string)
  const notFound = err('NotFound')

  // Useful for pattern matching
  if (result.isErr()) {
    switch (result.error) {
      case 'NotFound':
        return 404
      case 'Unauthorized':
        return 401
      default:
        return 500
    }
  }
  ```
</Accordion>

***

## v7.0.1

### Patch Changes

<Accordion title="Make safeTry type inference more strict">
  **Pull Request:** [#527](https://github.com/supermacro/neverthrow/pull/527)\
  **Contributor:** [@3846masa](https://github.com/3846masa)

  Changed type definitions to make inferring types of `safeTry` more strict and accurate.
</Accordion>

<Accordion title="Enhance match type inference">
  **Pull Request:** [#497](https://github.com/supermacro/neverthrow/pull/497)\
  **Contributor:** [@braxtonhall](https://github.com/braxtonhall)

  Enhanced type inference for the `match` method to better handle callback return types.
</Accordion>

***

## v7.0.0

### Major Changes

<Accordion title="Declare minimum Node.js version">
  **Pull Request:** [#553](https://github.com/supermacro/neverthrow/pull/553)\
  **Contributor:** [@m-shaka](https://github.com/m-shaka)

  Declared the minimum supported Node.js version in the `engines` field of `package.json`.

  **Requirements:**

  * Node.js: `>=18`
  * npm: `>=11`

  **Note:**

  `NeverThrow` does not depend on any Node.js version-specific features, so it should work with any version of Node.js that supports ES6 and other runtimes like browsers, Deno, etc.

  The engine declaration is primarily for maintaining a consistent development environment.
</Accordion>

***

## Earlier Versions

For a complete history of changes in versions prior to v7.0.0, please visit the [GitHub releases page](https://github.com/supermacro/neverthrow/releases).

## Release Channels

NeverThrow follows [semantic versioning](https://semver.org/):

* **Major versions** (x.0.0) contain breaking changes
* **Minor versions** (0.x.0) add new features in a backward-compatible manner
* **Patch versions** (0.0.x) contain bug fixes and documentation updates

## Stay Updated

* **Watch the repository** on [GitHub](https://github.com/supermacro/neverthrow) for release notifications
* **Follow releases** via [RSS feed](https://github.com/supermacro/neverthrow/releases.atom)
* **Subscribe to npm** updates for the [neverthrow package](https://www.npmjs.com/package/neverthrow)

## Contributing

Interested in contributing to NeverThrow?

* Check out [open issues](https://github.com/supermacro/neverthrow/issues)
* Read the [contributing guidelines](https://github.com/supermacro/neverthrow/blob/master/CONTRIBUTING.md)
* Join [GitHub Discussions](https://github.com/supermacro/neverthrow/discussions)

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