Simplify AuthenticationResponse.decodeIDToken guard logic

Author: dmitrizagidulin

src/AuthenticationResponse.js

@@ -356,24 +356,25 @@ class AuthenticationResponse {
   /**
    * decodeIDToken
    *
+   * Note: If the `id_token` is not present in params, this method does not
+   * get called (short-circuited in `validateIDToken()`).
+   *
    * @param response {AuthenticationResponse}
    * @param response.params {object}
-   * @param response.params.id_token {string} IDToken encoded as a JWT
+   * @param [response.params.id_token] {string} IDToken encoded as a JWT
    *
    * @returns {AuthenticationResponse} Chainable
    */
   static decodeIDToken (response) {
     let jwt = response.params.id_token
 
-    if (jwt) {
-      try {
-        response.decoded = IDToken.decode(jwt)
-      } catch (decodeError) {
-        const error = new HttpError(400, 'Error decoding ID Token')
-        error.cause = decodeError
-        error.info = { id_token: jwt }
-        throw error
-      }
+    try {
+      response.decoded = IDToken.decode(jwt)
+    } catch (decodeError) {
+      const error = new HttpError(400, 'Error decoding ID Token')
+      error.cause = decodeError
+      error.info = { id_token: jwt }
+      throw error
     }
 
     return response

test/AuthenticationResponseSpec.js

@@ -488,12 +488,6 @@ describe('AuthenticationResponse', () => {
         .should.be.instanceof(JWT)
     })
 
-    it('should ignore response without id_token', () => {
-      delete response.params.id_token
-      expect(AuthenticationResponse.decodeIDToken(response).decoded)
-        .to.be.undefined()
-    })
-
     it('should throw an error on invalid id_token', () => {
       response.params.id_token = 'inva1id'
       expect(() => {