Fix: Logging headers & errors fails when ConnectionFailed is raised (#…

…1512)

lib/faraday/logging/formatter.rb

@@ -56,6 +56,8 @@ def filter(filter_word, filter_replacement)
       private
 
       def dump_headers(headers)
+        return if headers.nil?
+
         headers.map { |k, v| "#{k}: #{v.inspect}" }.join("\n")
       end
 

spec/faraday/response/logger_spec.rb

@@ -25,6 +25,7 @@
         stubs.get('/filtered_headers') { [200, { 'Content-Type' => 'text/html' }, 'headers response'] }
         stubs.get('/filtered_params') { [200, { 'Content-Type' => 'text/html' }, 'params response'] }
         stubs.get('/filtered_url') { [200, { 'Content-Type' => 'text/html' }, 'url response'] }
+        stubs.get('/connection_failed') { raise Faraday::ConnectionFailed, 'Failed to open TCP connection' }
       end
     end
   end
@@ -216,6 +217,15 @@ def response(_env)
     end
   end
 
+  context 'when logging headers and errors' do
+    let(:logger_options) { { headers: true, errors: true } }
+
+    it 'logs error message' do
+      expect { conn.get '/connection_failed' }.to raise_error(Faraday::ConnectionFailed)
+      expect(string_io.string).to match(%(Failed to open TCP connection))
+    end
+  end
+
   context 'when using log_level' do
     let(:logger_options) { { bodies: true, log_level: :debug } }