If the client should redirect during AuthCodeGrant authorisation then provide a redirect uri

src/Exception/InvalidRequestException.php

@@ -30,7 +30,7 @@ class InvalidRequestException extends OAuthException
      * {@inheritdoc}
      */
 
-    public function __construct($parameter, $shouldRedirect = false)
+    public function __construct($parameter, $redirectUri = null)
     {
         parent::__construct(
             sprintf(
@@ -39,6 +39,6 @@ class InvalidRequestException extends OAuthException
             )
         );
 
-        $this->serverShouldRedirect = $shouldRedirect;
+        $this->redirectUri = $redirectUri;
     }
 }

src/Exception/InvalidScopeException.php

@@ -30,7 +30,7 @@ class InvalidScopeException extends OAuthException
      * {@inheritdoc}
      */
 
-    public function __construct($parameter, $shouldRedirect = false)
+    public function __construct($parameter, $redirectUri = null)
     {
         parent::__construct(
             sprintf(
@@ -39,6 +39,6 @@ class InvalidScopeException extends OAuthException
             )
         );
 
-        $this->serverShouldRedirect = $shouldRedirect;
+        $this->redirectUri = $redirectUri;
     }
 }

src/Exception/OAuthException.php

@@ -24,10 +24,10 @@ class OAuthException extends \Exception
     public $httpStatusCode = 400;
 
     /**
-     * If true the server should redirect back to the client
+     * Redirect URI if the server should redirect back to the client
-     * @var boolean
+     * @var string|null
      */
-    public $serverShouldRedirect = false;
+    public $redirectUri = null;
 
     /**
      * The exception type
@@ -48,7 +48,22 @@ class OAuthException extends \Exception
      */
     public function shouldRedirect()
     {
-        return $this->serverShouldRedirect;
+        return is_null($this->redirectUri) ? false : true;
+    }
+
+    /**
+     * Return redirect URI if set
+     * @return string|null
+     */
+    public function getRedirectUri()
+    {
+        return \League\OAuth2\Server\Util\RedirectUri::make(
+            $this->redirectUri,
+            [
+                'error' =>  $this->errorType,
+                'message' =>  $this->getMessage(),
+            ]
+        );
     }
 
     /**

src/Exception/UnsupportedResponseTypeException.php

@@ -29,9 +29,9 @@ class UnsupportedResponseTypeException extends OAuthException
     /**
      * {@inheritdoc}
      */
-    public function __construct($parameter)
+    public function __construct($parameter, $redirectUri = null)
     {
         parent::__construct('The authorization server does not support obtaining an access token using this method.');
-        $this->serverShouldRedirect = true;
+        $this->redirectUri = $redirectUri;
     }
 }

src/Grant/AbstractGrant.php

@@ -121,11 +121,12 @@ abstract class AbstractGrant implements GrantTypeInterface
     /**
      * Given a list of scopes, validate them and return an array of Scope entities
      * @param  string                                       $scopeParam  A string of scopes (e.g. "profile email birthday")
-     * @param  \League\OAuth2\Server\Entity\ClientEntity    $client      A string of scopes (e.g. "profile email birthday")
+     * @param  \League\OAuth2\Server\Entity\ClientEntity    $client      Client entity
+     * @param  string|null                                  $redirectUri The redirect URI to return the user to
      * @return \League\OAuth2\Server\Entity\ScopeEntity[]
-     * @throws \League\OAuth2\Server\Exception\ClientException           If scope is invalid, or no scopes passed when required
+     * @throws \League\OAuth2\Server\Exception\InvalidScopeException     If scope is invalid, or no scopes passed when required
      */
-    public function validateScopes($scopeParam = '', ClientEntity $client)
+    public function validateScopes($scopeParam = '', ClientEntity $client, $redirectUri = null)
     {
         $scopesList = explode($this->server->getScopeDelimeter(), $scopeParam);
 
@@ -160,7 +161,7 @@ abstract class AbstractGrant implements GrantTypeInterface
             );
 
             if (($scope instanceof ScopeEntity) === false) {
-                throw new Exception\InvalidScopeException($scopeItem, true);
+                throw new Exception\InvalidScopeException($scopeItem, $redirectUri);
             }
 
             $scopes[$scope->getId()] = $scope;

src/Grant/AuthCodeGrant.php

@@ -99,22 +99,22 @@ class AuthCodeGrant extends AbstractGrant
 
         $state = $this->server->getRequest()->query->get('state', null);
         if ($this->server->stateParamRequired() === true && is_null($state)) {
-            throw new Exception\InvalidRequestException('state', true);
+            throw new Exception\InvalidRequestException('state', $redirectUri);
         }
 
         $responseType = $this->server->getRequest()->query->get('response_type', null);
         if (is_null($responseType)) {
-            throw new Exception\InvalidRequestException('response_type', true);
+            throw new Exception\InvalidRequestException('response_type', $redirectUri);
         }
 
         // Ensure response type is one that is recognised
         if (!in_array($responseType, $this->server->getResponseTypes())) {
-            throw new Exception\UnsupportedResponseTypeException($responseType);
+            throw new Exception\UnsupportedResponseTypeException($responseType, $redirectUri);
         }
 
         // Validate any scopes that are in the request
         $scopeParam = $this->server->getRequest()->query->get('scope', '');
-        $scopes = $this->validateScopes($scopeParam, $client);
+        $scopes = $this->validateScopes($scopeParam, $client, $redirectUri);
 
         return [
             'client'        =>  $client,