Better handle errors that come from the actual app.

lib/omniauth/strategy.rb

@@ -193,6 +193,8 @@ def call!(env) # rubocop:disable CyclomaticComplexity, PerceivedComplexity
         return callback_call if on_callback_path?
         return other_phase if respond_to?(:other_phase)
       rescue StandardError => e
+        raise e if env.delete('omniauth.error.app')
+
         return fail!(e.message, e)
       end
 
@@ -302,6 +304,8 @@ def mock_call!(*)
         return mock_request_call if on_request_path? && OmniAuth.config.allowed_request_methods.include?(request.request_method.downcase.to_sym)
         return mock_callback_call if on_callback_path?
       rescue StandardError => e
+        raise e if env.delete('omniauth.error.app')
+
         return fail!(e.message, e)
       end
 
@@ -462,6 +466,9 @@ def query_string
 
     def call_app!(env = @env)
       @app.call(env)
+    rescue StandardError => e
+      env['omniauth.error.app'] = true
+      raise e
     end
 
     def full_host

spec/omniauth/strategy_spec.rb

@@ -629,6 +629,36 @@ def make_env(path = '/auth/test', props = {})
           expect(strategy.callback_url).to eq('http://example.com/myapp/override/callback')
         end
       end
+
+      context 'error during call_app!' do
+        class OtherPhaseStrategy < ExampleStrategy
+          def other_phase
+            call_app!
+          end
+        end
+        class AppError < StandardError; end
+        let(:app) { ->(_env) { raise(AppError.new('Some error in the app!')) } }
+        let(:strategy) { OtherPhaseStrategy.new(app) }
+
+        it 'raises the application error' do
+          expect { strategy.call(make_env('/some/path')) }.to raise_error(AppError, 'Some error in the app!')
+        end
+      end
+
+      context 'error during auth phase' do
+        class SomeStrategy < ExampleStrategy
+          def request_phase
+            raise AuthError.new('Some error in authentication')
+          end
+        end
+        class AuthError < StandardError; end
+        let(:strategy) { SomeStrategy.new(app) }
+
+        it 'passes the error to fail!()' do
+          expect(strategy).to receive(:fail!).with('Some error in authentication', kind_of(AuthError))
+          strategy.call(make_env('/auth/test', props))
+        end
+      end
     end