Allow OAuth2Client refresh token to be updated when grant_type is "refresh_token"

OAuth2.Tests/Client/OAuth2ClientTests.cs

@@ -177,6 +177,45 @@ public async Task Should_IssueCorrectRequestForUserInfo_When_GetUserInfoIsCalled
             _restClient.Authenticator.Should().BeOfType<OAuth2UriQueryParameterAuthenticator>();
         }
 
+        [Test]
+        public async Task Should_Update_RefreshToken_When_New_Token_Is_Provided_in_GetCurrentTokenAsync()
+        {
+            // arrange
+            var oldRefreshToken = "old-refresh-token";
+            var newRefreshToken = "new-refresh-token";
+            var response = @$"{{""access_token"": ""abc123"", ""refresh_token"": ""{newRefreshToken}""}}";
+            _restResponse.Content.Returns(response);
+
+            // act
+            await _descendant.GetCurrentTokenAsync(oldRefreshToken);
+
+            // assert
+            Assert.That(_descendant.RefreshToken, Is.EqualTo(newRefreshToken));
+        }
+
+        [Test]
+        public async Task Should_Not_Modify_RefreshToken_When_Not_Included_In_Response_From_GetCurrentTokenAsync()
+        {
+            // arrange
+            var currentRefreshToken = "refresh-token";
+            var initialTokenResponse = @$"{{""access_token"": ""abc123"", ""refresh_token"": ""{currentRefreshToken}""}}";
+            var refreshTokenResponse = @"{""access_token"": ""abc123""}";
+
+            // simulate getting the initial token (to populate refresh token)
+            _restResponse.Content.Returns(initialTokenResponse);
+            await _descendant.GetTokenAsync(new NameValueCollection {{"code", "auth-code"}});
+            Assert.That(_descendant.RefreshToken, Is.EqualTo(currentRefreshToken));
+
+            // setup response for refresh token request
+            _restResponse.Content.Returns(refreshTokenResponse);
+
+            // act
+            await _descendant.GetCurrentTokenAsync(currentRefreshToken);
+
+            // assert
+            Assert.That(_descendant.RefreshToken, Is.EqualTo(currentRefreshToken));
+        }
+
         class OAuth2ClientDescendant : OAuth2Client
         {
             public OAuth2ClientDescendant(IRequestFactory factory, IClientConfiguration configuration) 

OAuth2/Client/OAuth2Client.cs

@@ -206,8 +206,9 @@ private async Task QueryAccessTokenAsync(NameValueCollection parameters, Cancell
             if (String.IsNullOrEmpty(AccessToken))
                 throw new UnexpectedResponseException(AccessTokenKey);
 
-            if (GrantType != "refresh_token")
-                RefreshToken = ParseTokenResponse(response.Content, RefreshTokenKey);
+            string refreshToken = ParseTokenResponse(response.Content, RefreshTokenKey);
+            if (!String.IsNullOrWhiteSpace(refreshToken))
+                RefreshToken = refreshToken;
 
             TokenType = ParseTokenResponse(response.Content, TokenTypeKey);