Add custom message to _unsafeUnwrap*

.changeset/hip-cycles-clean.md

@@ -0,0 +1,5 @@
+---
+'neverthrow': minor
+---
+
+Add custom message to \_unsafeUnwrap

README.md

@@ -1571,9 +1571,17 @@ _unsafeUnwrapErr({
 
 // ^ Now the error object will have a `.stack` property containing the current stack
 ```
+You can also conditionally add a custom error message that will be propagated with the error object. By default this error message will be `Called '_unsafeUnwrap' on an Err` when called on an `Err` and `Called '_unsafeUnwrapErr' on an Ok` when called on an `Ok`.
 
----
+```typescript
+_unsafeUnwrapErr({
+  message: 'Your custom error message',
+  withStackTrace: true,
+})
+```
 
+---
+
 If you find this package useful, please consider [sponsoring me](https://github.com/sponsors/supermacro/) or simply [buying me a coffee](https://ko-fi.com/gdelgado)!
 
 ---

src/_internals/error.ts

@@ -1,7 +1,8 @@
 import { Result } from '../result'
 
 export interface ErrorConfig {
-  withStackTrace: boolean
+  withStackTrace?: boolean
+  message?: string
 }
 
 const defaultErrorConfig: ErrorConfig = {

src/result.ts

@@ -379,7 +379,11 @@ export class Ok<T, E> implements IResult<T, E> {
   }
 
   _unsafeUnwrapErr(config?: ErrorConfig): E {
-    throw createNeverThrowError('Called `_unsafeUnwrapErr` on an Ok', this, config)
+    throw createNeverThrowError(
+      config?.message ?? 'Called `_unsafeUnwrapErr` on an Ok',
+      this,
+      config,
+    )
   }
 }
 
@@ -461,7 +465,7 @@ export class Err<T, E> implements IResult<T, E> {
   }
 
   _unsafeUnwrap(config?: ErrorConfig): T {
-    throw createNeverThrowError('Called `_unsafeUnwrap` on an Err', this, config)
+    throw createNeverThrowError(config?.message ?? 'Called `_unsafeUnwrap` on an Err', this, config)
   }
 
   _unsafeUnwrapErr(_?: ErrorConfig): E {