feat: add payload generics to jose.decodeJwt

fixes #604
panva · Nov 3, 2023 · 9de49e2 · 9de49e2
1 parent b4f3b61
commit 9de49e2
Show file tree

Hide file tree

Showing 3 changed files with 23 additions and 4 deletions.
diff --git a/docs/functions/util_decode_jwt.decodeJwt.md b/docs/functions/util_decode_jwt.decodeJwt.md
@@ -6,13 +6,19 @@ Support from the community to continue maintaining and improving this module is
 
 ---
 
-▸ **decodeJwt**(`jwt`): [`JWTPayload`](../interfaces/types.JWTPayload.md)
+▸ **decodeJwt**<`PayloadType`\>(`jwt`): `PayloadType` & [`JWTPayload`](../interfaces/types.JWTPayload.md)
 
 Decodes a signed JSON Web Token payload. This does not validate the JWT Claims Set types or
 values. This does not validate the JWS Signature. For a proper Signed JWT Claims Set validation
 and JWS signature verification use `jose.jwtVerify()`. For an encrypted JWT Claims Set validation
 and JWE decryption use `jose.jwtDecrypt()`.
 
+#### Type parameters
+
+| Name | Type |
+| :------ | :------ |
+| `PayloadType` | [`JWTPayload`](../interfaces/types.JWTPayload.md) |
+
 #### Parameters
 
 | Name | Type | Description |
@@ -21,7 +27,7 @@ and JWE decryption use `jose.jwtDecrypt()`.
 
 #### Returns
 
-[`JWTPayload`](../interfaces/types.JWTPayload.md)
+`PayloadType` & [`JWTPayload`](../interfaces/types.JWTPayload.md)
 
 **`Example`**
 

diff --git a/src/util/decode_jwt.ts b/src/util/decode_jwt.ts
@@ -19,7 +19,7 @@ import { JWTInvalid } from './errors.js'
  *
  * @param jwt JWT token in compact JWS serialization.
  */
-export function decodeJwt(jwt: string) {
+export function decodeJwt<PayloadType = JWTPayload>(jwt: string): PayloadType & JWTPayload {
  if (typeof jwt !== 'string')
  throw new JWTInvalid('JWTs must use Compact JWS serialization, JWT must be a string')
 
@@ -43,7 +43,7 @@ export function decodeJwt(jwt: string) {
  throw new JWTInvalid('Failed to parse the decoded payload as JSON')
  }
 
- if (!isObject<JWTPayload>(result)) throw new JWTInvalid('Invalid JWT Claims Set')
+ if (!isObject<PayloadType & JWTPayload>(result)) throw new JWTInvalid('Invalid JWT Claims Set')
 
  return result
 }
diff --git a/test/types/index.test-d.ts b/test/types/index.test-d.ts
@@ -230,6 +230,13 @@ expectType<KeyObject>(await lib.EmbeddedJWK())
  expectType<'string'>(result.payload.foo)
 }
 
+{
+ const result = lib.decodeJwt<{ foo: 'string' }>('')
+ expectType<string | undefined>(result.iss)
+ expectType<unknown>(result.unknown)
+ expectType<'string'>(result.foo)
+}
+
 {
  const result = await lib.jwtVerify('', new Uint8Array())
  expectType<string | undefined>(result.payload.iss)
@@ -247,3 +254,9 @@ expectType<KeyObject>(await lib.EmbeddedJWK())
  expectType<string | undefined>(result.payload.iss)
  expectType<unknown>(result.payload.unknown)
 }
+
+{
+ const result = lib.decodeJwt('')
+ expectType<string | undefined>(result.iss)
+ expectType<unknown>(result.unknown)
+}