feat: allow specifying error message function

So that you can provide a custom error message that includes the value
aikoven · Jul 6, 2024 · 2cba510 · 2cba510
1 parent 5259e13
commit 2cba510
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/index.ts b/index.ts
@@ -1,4 +1,5 @@
 export function assertNever(value: never, errorMessage?: string): never
+export function assertNever(value: never, getErrorMessage?: (value: unknown) => string): never
 export function assertNever(value: never, noThrow?: boolean): never
 
 /**
@@ -26,11 +27,15 @@ export function assertNever(value: never, noThrow?: boolean): never
  *      return assertNever(arg);
  *    }
  */
-export function assertNever(value: never, errorMessageOrNoThrow?: string | boolean): never {
+export function assertNever(value: never, errorMessageOrNoThrow?: string | ((value: unknown) => string) | boolean): never {
   if (typeof errorMessageOrNoThrow === 'string') {
     throw new Error(errorMessageOrNoThrow)
   }
 
+  if (typeof errorMessageOrNoThrow === 'function') {
+    throw new Error(errorMessageOrNoThrow(value))
+  }
+
   if (errorMessageOrNoThrow) {
     return value
   }