filters: add optional DependencyFilter

The filter allows keeping track of the app's dependencies.

CHANGELOG.md

@@ -5,6 +5,8 @@ Airbrake Ruby Changelog
 
 * Added the `versions` option
   ([#327](https://github.com/airbrake/airbrake-ruby/pull/327))
+* Added `DependencyFilter` (optional)
+  ([#328](https://github.com/airbrake/airbrake-ruby/pull/328))
 
 ### [v2.9.0][v2.9.0] (April 26, 2018)
 

README.md

@@ -47,6 +47,7 @@ Key features
 * Severity support<sup>[[link](#setting-severity)]</sup>
 * Support for code hunks (lines of code surrounding each backtrace frame)<sup>[[link](#code_hunks)]</sup>
 * Ability to add context to reported exceptions<sup>[[link](#airbrakemerge_context)]</sup>
+* Dependency tracking<sup>[[link](#airbrakefiltersdependencyfilter)]</sup>
 * Last but not least, we follow semantic versioning 2.0.0<sup>[[link][semver2]]</sup>
 
 Installation
@@ -568,14 +569,26 @@ every type of application, so there's no need to include them only to clutter
 the notice object. You have to include such filters manually, if you think you
 need them. The list of optional filters include:
 
-* Airbrake::Filters::ThreadFilter
+###### Airbrake::Filters::ThreadFilter
 
-Adding them is as easy as:
+Attaches thread & fiber local variables along with general thread information.
 
 ```ruby
 Airbrake.add_filter(Airbrake::Filters::ThreadFilter.new)
 ```
 
+###### Airbrake::Filters::DependencyFilter
+
+Attaches loaded dependencies to the notice object (under
+`context/versions/dependencies`).
+
+```ruby
+Airbrake.add_filter(Airbrake::Filters::DependencyFilter.new)
+```
+
+Adding them is as easy as:
+
+
 ##### Using classes for building filters
 
 For more complex filters you can use the special API. Simply pass an object that

lib/airbrake-ruby.rb

@@ -25,6 +25,7 @@
 require 'airbrake-ruby/filters/thread_filter'
 require 'airbrake-ruby/filters/context_filter'
 require 'airbrake-ruby/filters/exception_attributes_filter'
+require 'airbrake-ruby/filters/dependency_filter'
 require 'airbrake-ruby/filter_chain'
 require 'airbrake-ruby/notifier'
 require 'airbrake-ruby/code_hunk'

lib/airbrake-ruby/filters/dependency_filter.rb

@@ -0,0 +1,27 @@
+module Airbrake
+  module Filters
+    # Attaches loaded dependencies to the notice object.
+    class DependencyFilter
+      def initialize
+        @weight = 117
+      end
+
+      def call(notice)
+        deps = {}
+        Gem.loaded_specs.map.with_object(deps) do |(name, spec), h|
+          h[name] = "#{spec.version}#{git_version(spec)}"
+        end
+
+        notice[:context][:versions] = {} unless notice[:context].key?(:versions)
+        notice[:context][:versions][:dependencies] = deps
+      end
+
+      private
+
+      def git_version(spec)
+        return unless spec.respond_to?(:git_version) || spec.git_version
+        spec.git_version.to_s
+      end
+    end
+  end
+end

spec/filters/dependency_filter_spec.rb

@@ -0,0 +1,16 @@
+require 'spec_helper'
+
+RSpec.describe Airbrake::Filters::DependencyFilter do
+  let(:notice) do
+    Airbrake::Notice.new(Airbrake::Config.new, AirbrakeTestError.new)
+  end
+
+  describe "#call" do
+    it "attaches loaded dependencies to context/versions/dependencies" do
+      subject.call(notice)
+      expect(notice[:context][:versions][:dependencies]).to include(
+        'airbrake-ruby' => Airbrake::AIRBRAKE_RUBY_VERSION
+      )
+    end
+  end
+end