Fix preserving existing query parameters in redirect_uri

Author: liggitt

response.go

@@ -117,8 +117,16 @@ func (r *Response) GetRedirectUrl() (string, error) {
 		return "", err
 	}
 
+	var q url.Values
+	if r.RedirectInFragment {
+		// start with empty set for fragment
+		q = url.Values{}
+	} else {
+		// add parameters to existing query
+		q = u.Query()
+	}
+
 	// add parameters
-	q := u.Query()
 	for n, v := range r.Output {
 		q.Set(n, fmt.Sprint(v))
 	}
@@ -127,7 +135,6 @@ func (r *Response) GetRedirectUrl() (string, error) {
 	// Fragment should be encoded as application/x-www-form-urlencoded (%-escaped, spaces are represented as '+')
 	// The stdlib URL#String() doesn't make that easy to accomplish, so build this ourselves
 	if r.RedirectInFragment {
-		u.RawQuery = ""
 		u.Fragment = ""
 		redirectURI := u.String() + "#" + q.Encode()
 		return redirectURI, nil

response_test.go

@@ -18,18 +18,18 @@ func TestGetRedirectUrl(t *testing.T) {
 		ExpectedURL string
 	}{
 		"query": {
-			URL:         "https://foo.com/path",
+			URL:         "https://foo.com/path?abc=123",
 			Output:      ResponseData{"access_token": "12345", "state": state},
-			ExpectedURL: "https://foo.com/path?access_token=12345&state=%7B%22then%22%3A+%22%2Findex.html%3Fa%3D1%26b%3D%252B%23fragment%22%2C+%22nonce%22%3A+%22014f%3Abff9a07c%22%7D",
+			ExpectedURL: "https://foo.com/path?abc=123&access_token=12345&state=%7B%22then%22%3A+%22%2Findex.html%3Fa%3D1%26b%3D%252B%23fragment%22%2C+%22nonce%22%3A+%22014f%3Abff9a07c%22%7D",
 		},
 
 		// https://tools.ietf.org/html/rfc6749#section-4.2.2
 		// Fragment should be encoded as application/x-www-form-urlencoded (%-escaped, spaces are represented as '+')
 		"fragment": {
-			URL:                "https://foo.com/path",
+			URL:                "https://foo.com/path?abc=123",
 			Output:             ResponseData{"access_token": "12345", "state": state},
 			RedirectInFragment: true,
-			ExpectedURL:        "https://foo.com/path#access_token=12345&state=%7B%22then%22%3A+%22%2Findex.html%3Fa%3D1%26b%3D%252B%23fragment%22%2C+%22nonce%22%3A+%22014f%3Abff9a07c%22%7D",
+			ExpectedURL:        "https://foo.com/path?abc=123#access_token=12345&state=%7B%22then%22%3A+%22%2Findex.html%3Fa%3D1%26b%3D%252B%23fragment%22%2C+%22nonce%22%3A+%22014f%3Abff9a07c%22%7D",
 		},
 	}