From 33c7afa2916a0944436b72867aaaa5b2d0fc9173 Mon Sep 17 00:00:00 2001
From: Nikita Bulai <bulaj.nikita@gmail.com>
Date: Mon, 12 Feb 2024 11:31:20 +0300
Subject: [PATCH] Make new errors backward compatible

Fixes #1685
---
 CHANGELOG.md                           |  1 +
 lib/doorkeeper/oauth/error_response.rb | 16 ++++++++++++++--
 spec/lib/oauth/error_response_spec.rb  |  7 +++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fe6cbd949..85697b57c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ User-visible changes worth mentioning.
 ## main
 
 - [#PR ID] Add your changelog here.
+- [#1691] Make new Doorkeeper errors backward compatible with older extensions.
 
 ## 5.6.8
 
diff --git a/lib/doorkeeper/oauth/error_response.rb b/lib/doorkeeper/oauth/error_response.rb
index 8301b8fc3..27463061c 100644
--- a/lib/doorkeeper/oauth/error_response.rb
+++ b/lib/doorkeeper/oauth/error_response.rb
@@ -10,14 +10,26 @@ class ErrorResponse < BaseResponse
       def self.from_request(request, attributes = {})
         new(
           attributes.merge(
-            name: request.error&.name_for_response,
-            exception_class: request.error,
+            name: error_name_for(request.error),
+            exception_class: exception_class_for(request.error),
             state: request.try(:state),
             redirect_uri: request.try(:redirect_uri),
           ),
         )
       end
 
+      def self.error_name_for(error)
+        error.respond_to?(:name_for_response) ? error.name_for_response : error
+      end
+
+      def self.exception_class_for(error)
+        return error if error.respond_to?(:name_for_response)
+
+        "Doorkeeper::Errors::#{error.to_s.classify}".safe_constantize
+      end
+
+      private_class_method :error_name_for, :exception_class_for
+
       delegate :name, :description, :state, to: :@error
 
       def initialize(attributes = {})
diff --git a/spec/lib/oauth/error_response_spec.rb b/spec/lib/oauth/error_response_spec.rb
index 9bb3acc41..0f7a5f374 100644
--- a/spec/lib/oauth/error_response_spec.rb
+++ b/spec/lib/oauth/error_response_spec.rb
@@ -36,6 +36,13 @@
       error = described_class.from_request double(error: Doorkeeper::Errors::InvalidClient, state: :hello)
       expect(error.state).to eq(:hello)
     end
+
+    it "supports old extensions" do
+      error = described_class.from_request double(error: :invalid_client)
+      expect(error.name).to eq(:invalid_client)
+
+      expect { error.raise_exception! }.to raise_error(Doorkeeper::Errors::InvalidClient)
+    end
   end
 
   it "ignores empty error values" do