issue #572: add Listen.adapter_warn_behavior =

README.md

@@ -155,7 +155,7 @@ Note: `:only` regexp patterns are evaluated only against relative **file** paths
 
 All the following options can be set through the `Listen.to` after the directory path(s) params.
 
-```ruby
+``` ruby
 ignore: [%r{/foo/bar}, /\.pid$/, /\.coffee$/]   # Ignore a list of paths
                                                 # default: See DEFAULT_IGNORED_FILES and DEFAULT_IGNORED_EXTENSIONS in Listen::Silencer
 
@@ -187,7 +187,7 @@ This is the primary method of debugging.
 
 ### Custom Logger
 You can call `Listen.logger =` to set a custom `listen` logger for the process. For example:
-```
+``` ruby
 Listen.logger = Rails.logger
 ```
 
@@ -197,7 +197,7 @@ If no custom logger is set, a default `listen` logger which logs to to `STDERR`
 The default logger defaults to the `error` logging level (severity).
 You can override the logging level by setting the environment variable `LISTEN_GEM_DEBUGGING=<level>`.
 For `<level>`, all standard `::Logger` levels are supported, with any mix of upper-/lower-case:
-```
+``` ruby
 export LISTEN_GEM_DEBUGGING=debug # or 2 [deprecated]
 export LISTEN_GEM_DEBUGGING=info  # or 1 or true or yes [deprecated]
 export LISTEN_GEM_DEBUGGING=warn
@@ -210,9 +210,36 @@ Note: The alternate values `1`, `2`, `true` and `yes` shown above are deprecated
 
 ### Disabling Logging
 If you want to disable `listen` logging, set
-```
+``` ruby
 Listen.logger = ::Logger.new('/dev/null')
 ```
+
+### Adapter Warnings
+If listen is having trouble with the underlying adapter, it will display warnings with `Kernel#warn` by default,
+which in turn writes to STDERR.
+Sometimes this is not desirable, for example in an environment where STDERR is ignored.
+For these reasons, the behavior can be configured using `Listen.adapter_warn_behavior =`:
+``` ruby
+Listen.adapter_warn_behavior = :warn   # default (true means the same)
+Listen.adapter_warn_behavior = :log    # send to logger.warn
+Listen.adapter_warn_behavior = :silent # suppress all adapter warnings (nil or false mean the same)
+```
+Also there are some cases where specific warnings are not helpful.
+For example, if you are using the polling adapter--and expect to--you can suppress the warning about it
+by providing a callable object like a lambda or proc that determines the behavior based on the `message`:
+``` ruby
+Listen.adapter_warn_behavior = ->(message) do
+  case message
+  when /Listen will be polling for changes/
+    :silent
+  when /directory is already being watched/
+    :log
+  else
+    :warn
+  end
+end
+```
+
 ## Listen Adapters
 
 The `Listen` gem has a set of adapters to notify it when there are changes.

lib/listen/logger.rb

@@ -6,13 +6,27 @@ module Listen
   # Listen.logger will always be present.
   # If you don't want logging, set Listen.logger = ::Logger.new('/dev/null', level: ::Logger::UNKNOWN)
 
+  @adapter_warn_behavior = :warn
+
   class << self
     attr_writer :logger
+    attr_accessor :adapter_warn_behavior
 
     def logger
       @logger ||= default_logger
     end
 
+    def adapter_warn(message)
+      case adapter_warn_behavior_callback(message)
+      when :log
+        logger.warn(message)
+      when :silent, nil, false
+        # do nothing
+      else # :warn
+        warn(message)
+      end
+    end
+
     private
 
     def default_logger
@@ -32,5 +46,20 @@ def default_logger
 
       ::Logger.new(STDERR, level: level)
     end
+
+    def adapter_warn_behavior_callback(message)
+      if adapter_warn_behavior.respond_to?(:call)
+        case behavior = adapter_warn_behavior.call(message)
+        when Symbol
+          behavior
+        when false, nil
+          :silent
+        else
+          :warn
+        end
+      else
+        adapter_warn_behavior
+      end
+    end
   end
 end

spec/lib/listen/logger_spec.rb

@@ -2,11 +2,7 @@
 
 require 'listen/logger'
 
-RSpec.describe 'Listen.logger' do
-  ENV_VARIABLE_NAME = 'LISTEN_GEM_DEBUGGING'
-
-  let(:logger) { instance_double(::Logger, "logger") }
-
+RSpec.describe 'logger.rb' do
   around do |spec|
     orig_logger = Listen.instance_variable_get(:@logger)
 
@@ -15,71 +11,167 @@
     Listen.logger = orig_logger
   end
 
-  around do |spec|
-    orig_debugging_env_variable = ENV.fetch(ENV_VARIABLE_NAME, :not_set)
+  describe 'Listen.logger' do
+    ENV_VARIABLE_NAME = 'LISTEN_GEM_DEBUGGING'
 
-    spec.run
+    let(:logger) { instance_double(::Logger, "logger") }
+
+    around do |spec|
+      orig_debugging_env_variable = ENV.fetch(ENV_VARIABLE_NAME, :not_set)
 
-    if orig_debugging_env_variable == :not_set
-      ENV.delete(ENV_VARIABLE_NAME)
-    else
-      ENV[ENV_VARIABLE_NAME] = orig_debugging_env_variable
+      spec.run
+
+      if orig_debugging_env_variable == :not_set
+        ENV.delete(ENV_VARIABLE_NAME)
+      else
+        ENV[ENV_VARIABLE_NAME] = orig_debugging_env_variable
+      end
     end
-  end
 
-  describe 'logger=' do
-    it 'allows the logger to be set' do
-      Listen.logger = logger
-      expect(Listen.logger).to be(logger)
+    describe 'logger=' do
+      it 'allows the logger to be set' do
+        Listen.logger = logger
+        expect(Listen.logger).to be(logger)
+      end
+
+      it 'allows nil to be set (implying default logger)' do
+        Listen.logger = nil
+        expect(Listen.logger).to be_kind_of(::Logger)
+      end
     end
 
-    it 'allows nil to be set (implying default logger)' do
-      Listen.logger = nil
-      expect(Listen.logger).to be_kind_of(::Logger)
+    describe 'logger' do
+      before do
+        Listen.instance_variable_set(:@logger, nil)
+      end
+
+      it 'returns default logger if none set' do
+        expect(Listen.logger).to be_kind_of(::Logger)
+      end
+
+      ['debug', 'DEBUG', '2', 'level2', '2 '].each do |env_value|
+        it "infers DEBUG level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
+          ENV[ENV_VARIABLE_NAME] = env_value
+          expect(Listen.logger.level).to eq(::Logger::DEBUG)
+        end
+      end
+
+      ['info', 'INFO', 'true', ' true', 'TRUE', 'TRUE ', 'yes', 'YES', ' yesss!', '1', 'level1'].each do |env_value|
+        it "infers INFO level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
+          ENV[ENV_VARIABLE_NAME] = env_value
+          expect(Listen.logger.level).to eq(::Logger::INFO)
+        end
+      end
+
+      ['warn', 'WARN', ' warn', 'warning'].each do |env_value|
+        it "infers WARN level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
+          ENV[ENV_VARIABLE_NAME] = env_value
+          expect(Listen.logger.level).to eq(::Logger::WARN)
+        end
+      end
+
+      ['error', 'ERROR', 'OTHER'].each do |env_value|
+        it "infers ERROR level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
+          ENV[ENV_VARIABLE_NAME] = env_value
+          expect(Listen.logger.level).to eq(::Logger::ERROR)
+        end
+      end
+
+      ['fatal', 'FATAL', ' fatal'].each do |env_value|
+        it "infers FATAL level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
+          ENV[ENV_VARIABLE_NAME] = env_value
+          expect(Listen.logger.level).to eq(::Logger::FATAL)
+        end
+      end
     end
   end
 
-  describe 'logger' do
-    before do
-      Listen.instance_variable_set(:@logger, nil)
+  describe 'Listen.adapter_warn_behavior' do
+    subject { Listen.adapter_warn(message) }
+
+    after do
+      Listen.adapter_warn_behavior = :warn
     end
+    let(:message) { "warning message" }
 
-    it 'returns default logger if none set' do
-      expect(Listen.logger).to be_kind_of(::Logger)
+    it 'defaults to :warn' do
+      expect(Listen.adapter_warn_behavior).to eq(:warn)
+
+      expect(Listen).to receive(:warn).with(message)
+
+      subject
     end
 
-    ['debug', 'DEBUG', '2', 'level2', '2 '].each do |env_value|
-      it "infers DEBUG level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
-        ENV[ENV_VARIABLE_NAME] = env_value
-        expect(Listen.logger.level).to eq(::Logger::DEBUG)
-      end
+    it 'allows the adapter_warn_behavior to be set to :log' do
+      Listen.adapter_warn_behavior = :log
+
+      expect(Listen.logger).to receive(:warn).with(message)
+
+      subject
     end
 
-    ['info', 'INFO', 'true', ' true', 'TRUE', 'TRUE ', 'yes', 'YES', ' yesss!', '1', 'level1'].each do |env_value|
-      it "infers INFO level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
-        ENV[ENV_VARIABLE_NAME] = env_value
-        expect(Listen.logger.level).to eq(::Logger::INFO)
+    [:silent, nil, false].each do |behavior|
+      it "allows the adapter_warn_behavior to be set to #{behavior} to silence the warnings" do
+        Listen.adapter_warn_behavior = behavior
+
+        expect(Listen.logger).not_to receive(:warn)
+        expect(Listen).not_to receive(:warn)
+
+        subject
       end
     end
 
-    ['warn', 'WARN', ' warn', 'warning'].each do |env_value|
-      it "infers WARN level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
-        ENV[ENV_VARIABLE_NAME] = env_value
-        expect(Listen.logger.level).to eq(::Logger::WARN)
+    context 'when adapter_warn_behavior is set to a callable object like a proc' do
+      before do
+        Listen.adapter_warn_behavior = ->(message) do
+          case message
+          when /USE warn/
+            :warn
+          when /USE log/
+            :log
+          when /USE silent/
+            :silent
+          when /USE false/
+            false
+          when /USE nil/
+            nil
+          else
+            true
+          end
+        end
       end
-    end
 
-    ['error', 'ERROR', 'OTHER'].each do |env_value|
-      it "infers ERROR level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
-        ENV[ENV_VARIABLE_NAME] = env_value
-        expect(Listen.logger.level).to eq(::Logger::ERROR)
+      [true, :warn].each do |behavior|
+        context "when the message matches a #{behavior.inspect} pattern" do
+          let(:message) { "USE #{behavior.inspect}" }
+          it 'respects :warn' do
+            expect(Listen).to receive(:warn).with(message)
+
+            subject
+          end
+        end
       end
-    end
 
-    ['fatal', 'FATAL', ' fatal'].each do |env_value|
-      it "infers FATAL level from #{ENV_VARIABLE_NAME}=#{env_value.inspect}" do
-        ENV[ENV_VARIABLE_NAME] = env_value
-        expect(Listen.logger.level).to eq(::Logger::FATAL)
+      context 'when the message matches a :silent pattern' do
+        let(:message) { "USE silent" }
+        it 'respects :silent' do
+          expect(Listen).not_to receive(:warn).with(message)
+          expect(Listen).not_to receive(:warn)
+
+          subject
+        end
+      end
+
+      [false, nil].each do |behavior|
+        context 'when the message matches a #{behavior} pattern' do
+          let(:message) { "USE #{behavior.inspect}" }
+          it 'respects :silent' do
+            expect(Listen).not_to receive(:warn).with(message)
+            expect(Listen).not_to receive(:warn)
+
+            subject
+          end
+        end
       end
     end
   end