Add the log formatter that is easy to override and safe to inherit

README.md

@@ -73,6 +73,23 @@ conn = Faraday.new(:url => 'http://sushi.com/api_key=s3cr3t') do |faraday|
   end
   faraday.adapter  Faraday.default_adapter  # make requests with Net::HTTP
 end
+
+# Override the log formatting on demand
+
+class MyFormatter < Faraday::Response::Logger::Formatter
+  def request(env)
+    info('Request', env)  
+  end
+
+  def request(env)
+    info('Response', env)
+  end
+end
+
+conn = Faraday.new(:url => 'http://sushi.com/api_key=s3cr3t') do |faraday|
+  faraday.response :logger, StructLogger.new(STDOUT), formatter: MyFormatter
+end
+
 ```
 
 Once you have the connection object, use it to make HTTP requests. You can pass parameters to it in a few different ways:

lib/faraday/logging/formatter.rb

@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+require 'pp'
+module Faraday
+  module Logging
+    # Serves as an integration point to customize logging
+    class Formatter
+      extend Forwardable
+
+      DEFAULT_OPTIONS = { headers: true, bodies: false }.freeze
+
+      def initialize(logger:, options:)
+        @logger = logger
+        @filter = []
+        @options = DEFAULT_OPTIONS.merge(options)
+      end
+
+      def_delegators :@logger, :debug, :info, :warn, :error, :fatal
+
+      def request(env)
+        info('request')  { "#{env.method.upcase} #{apply_filters(env.url.to_s)}" }
+        debug('request') { apply_filters(dump_headers(env.request_headers)) } if log_headers?(:request)
+        debug('request') { apply_filters(dump_body(env[:body])) } if env[:body] && log_body?(:request)
+      end
+
+      def response(env)
+        info('response')  { "Status #{env.status}" }
+        debug('response') { apply_filters(dump_headers(env.response_headers)) } if log_headers?(:response)
+        debug('response') { apply_filters(dump_body(env[:body])) } if env[:body] && log_body?(:response)
+      end
+
+      def filter(filter_word, filter_replacement)
+        @filter.push([filter_word, filter_replacement])
+      end
+
+      private
+
+      def dump_headers(headers)
+        headers.map { |k, v| "#{k}: #{v.inspect}" }.join("\n")
+      end
+
+      def dump_body(body)
+        if body.respond_to?(:to_str)
+          body.to_str
+        else
+          pretty_inspect(body)
+        end
+      end
+
+      def pretty_inspect(body)
+        body.pretty_inspect
+      end
+
+      def log_headers?(type)
+        case @options[:headers]
+        when Hash then @options[:headers][type]
+        else @options[:headers]
+        end
+      end
+
+      def log_body?(type)
+        case @options[:bodies]
+        when Hash then @options[:bodies][type]
+        else @options[:bodies]
+        end
+      end
+
+      def apply_filters(output)
+        @filter.each do |pattern, replacement|
+          output = output.to_s.gsub(pattern, replacement)
+        end
+        output
+      end
+    end
+  end
+end

lib/faraday/response/logger.rb

@@ -1,82 +1,29 @@
 # frozen_string_literal: true
 
 require 'forwardable'
+require 'faraday/logging/formatter'
 
 module Faraday
   class Response
     class Logger < Middleware
-      extend Forwardable
-
-      DEFAULT_OPTIONS = { headers: true, bodies: false }.freeze
-
       def initialize(app, logger = nil, options = {})
         super(app)
-        @logger = logger || begin
+        logger ||= begin
           require 'logger'
           ::Logger.new($stdout)
         end
-        @filter = []
-        @options = DEFAULT_OPTIONS.merge(options)
-        yield self if block_given?
+        formatter_class = options.delete(:formatter) || Logging::Formatter
+        @formatter = formatter_class.new(logger: logger, options: options)
+        yield @formatter if block_given?
       end
 
-      def_delegators :@logger, :debug, :info, :warn, :error, :fatal
-
       def call(env)
-        info('request')  { "#{env.method.upcase} #{apply_filters(env.url.to_s)}" }
-        debug('request') { apply_filters(dump_headers(env.request_headers)) } if log_headers?(:request)
-        debug('request') { apply_filters(dump_body(env[:body])) } if env[:body] && log_body?(:request)
+        @formatter.request(env)
         super
       end
 
       def on_complete(env)
-        info('response')  { "Status #{env.status}" }
-        debug('response') { apply_filters(dump_headers(env.response_headers)) } if log_headers?(:response)
-        debug('response') { apply_filters(dump_body(env[:body])) } if env[:body] && log_body?(:response)
-      end
-
-      def filter(filter_word, filter_replacement)
-        @filter.push([filter_word, filter_replacement])
-      end
-
-      private
-
-      def dump_headers(headers)
-        headers.map { |k, v| "#{k}: #{v.inspect}" }.join("\n")
-      end
-
-      def dump_body(body)
-        if body.respond_to?(:to_str)
-          body.to_str
-        else
-          pretty_inspect(body)
-        end
-      end
-
-      def pretty_inspect(body)
-        require 'pp' unless body.respond_to?(:pretty_inspect)
-        body.pretty_inspect
-      end
-
-      def log_headers?(type)
-        case @options[:headers]
-        when Hash then @options[:headers][type]
-        else @options[:headers]
-        end
-      end
-
-      def log_body?(type)
-        case @options[:bodies]
-        when Hash then @options[:bodies][type]
-        else @options[:bodies]
-        end
-      end
-
-      def apply_filters(output)
-        @filter.each do |pattern, replacement|
-          output = output.to_s.gsub(pattern, replacement)
-        end
-        output
+        @formatter.response(env)
       end
     end
   end

spec/faraday/response/logger_spec.rb

@@ -38,6 +38,61 @@
     expect(resp.body).to eq('hello')
   end
 
+  context 'without configuration' do
+    let(:conn) do
+      Faraday.new do |b|
+        b.response :logger
+        b.adapter :test do |stubs|
+          stubs.get('/hello') { [200, { 'Content-Type' => 'text/html' }, 'hello'] }
+        end
+      end
+    end
+
+    it 'defaults to stdout' do
+      expect(Logger).to receive(:new).with($stdout).and_return(Logger.new(nil))
+      conn.get('/hello')
+    end
+  end
+
+  context 'with default formatter' do
+    let(:formatter) { instance_double(Faraday::Logging::Formatter, request: true, response: true, filter: []) }
+
+    before { allow(Faraday::Logging::Formatter).to receive(:new).and_return(formatter) }
+
+    it 'delegates logging to the formatter' do
+      expect(formatter).to receive(:request).with(an_instance_of(Faraday::Env))
+      expect(formatter).to receive(:response).with(an_instance_of(Faraday::Env))
+      conn.get '/hello'
+    end
+  end
+
+  context 'with custom formatter' do
+    let(:formatter_class) do
+      Class.new(Faraday::Logging::Formatter) do
+        def initialize(*args)
+          super
+        end
+
+        def request(_env)
+          info 'Custom log formatter request'
+        end
+
+        def response(_env)
+          info 'Custom log formatter response'
+        end
+      end
+    end
+
+    let(:logger_options) { { formatter: formatter_class } }
+
+    it 'logs with custom formatter' do
+      conn.get '/hello'
+
+      expect(string_io.string).to match('Custom log formatter request')
+      expect(string_io.string).to match('Custom log formatter response')
+    end
+  end
+
   it 'logs method and url' do
     conn.get '/hello', nil, accept: 'text/html'
     expect(string_io.string).to match('GET http:/hello')