Better method of ensuring that args are not mutated by plugin initialize

add test for subclasses of codec, filter, input and output

Register codec clone, use String clone not dup so frozen strings stay so

Fixes #4444

Fixes #4473

logstash-core/lib/logstash/codecs/base.rb

@@ -11,7 +11,7 @@ module LogStash::Codecs; class Base < LogStash::Plugin
 
   def initialize(params={})
     super
-    config_init(params)
+    config_init(@params)
     register if respond_to?(:register)
   end
 
@@ -27,7 +27,7 @@ module LogStash::Codecs; class Base < LogStash::Plugin
     raise "#{self.class}#encode must be overidden"
   end # def encode
 
-  public 
+  public
   def close; end;
 
   # @param block [Proc(event, data)] the callback proc passing the original event and the encoded event

logstash-core/lib/logstash/filters/base.rb

@@ -120,7 +120,7 @@ class LogStash::Filters::Base < LogStash::Plugin
   public
   def initialize(params)
     super
-    config_init(params)
+    config_init(@params)
     @threadsafe = true
   end # def initialize
 

logstash-core/lib/logstash/inputs/base.rb

@@ -53,7 +53,7 @@ class LogStash::Inputs::Base < LogStash::Plugin
     super
     @threadable = false
     @stop_called = Concurrent::AtomicBoolean.new(false)
-    config_init(params)
+    config_init(@params)
     @tags ||= []
   end # def initialize
 

logstash-core/lib/logstash/outputs/base.rb

@@ -60,7 +60,7 @@ class LogStash::Outputs::Base < LogStash::Plugin
   public
   def initialize(params={})
     super
-    config_init(params)
+    config_init(@params)
 
     # If we're running with a single thread we must enforce single-threaded concurrency by default
     # Maybe in a future version we'll assume output plugins are threadsafe
@@ -88,4 +88,4 @@ class LogStash::Outputs::Base < LogStash::Plugin
     # TODO: noop for now, remove this once we delete this call from all plugins
     true
   end # def output?
-end # class LogStash::Outputs::Base
+end # class LogStash::Outputs::Base

logstash-core/lib/logstash/plugin.rb

@@ -24,7 +24,7 @@ class LogStash::Plugin
 
   public
   def initialize(params=nil)
-    @params = params
+    @params = LogStash::Util.deep_clone(params)
     @logger = Cabin::Channel.get(LogStash)
   end
 

logstash-core/lib/logstash/util.rb

@@ -183,4 +183,21 @@ module LogStash::Util
       o
     end
   end
+
+  def self.deep_clone(o)
+    case o
+    when Hash
+      o.inject({}) {|h, (k,v)| h[k] = deep_clone(v); h }
+    when Array
+      o.map {|v| deep_clone(v) }
+    when Fixnum, Symbol, IO, TrueClass, FalseClass, NilClass
+      o
+    when LogStash::Codecs::Base
+      o.clone.tap {|c| c.register }
+    when String
+      o.clone #need to keep internal state e.g. frozen
+    else
+      Marshal.load(Marshal.dump(o))
+    end
+  end
 end # module LogStash::Util

logstash-core/spec/logstash/plugin_spec.rb

@@ -108,7 +108,7 @@ describe LogStash::Plugin do
 
       subject.validate({})
     end
-    
+
 
     it 'logs a warning if the plugin use the milestone option' do
       expect_any_instance_of(Cabin::Channel).to receive(:warn)
@@ -120,4 +120,33 @@ describe LogStash::Plugin do
       end
     end
   end
+
+  describe "subclass initialize" do
+    let(:args) { Hash.new }
+
+    [
+      StromaeCodec = Class.new(LogStash::Codecs::Base) do
+        config_name "stromae"
+        config :foo_tag, :validate => :string, :default => "bar"
+      end,
+      StromaeFilter = Class.new(LogStash::Filters::Base) do
+        config_name "stromae"
+        config :foo_tag, :validate => :string, :default => "bar"
+      end,
+      StromaeInput = Class.new(LogStash::Inputs::Base) do
+        config_name "stromae"
+        config :foo_tag, :validate => :string, :default => "bar"
+      end,
+      StromaeOutput = Class.new(LogStash::Outputs::Base) do
+        config_name "stromae"
+        config :foo_tag, :validate => :string, :default => "bar"
+      end
+    ].each do |klass|
+
+      it "subclass #{klass.name} does not modify params" do
+        instance = klass.new(args)
+        expect(args).to be_empty
+      end
+    end
+  end
 end