Add rollbar_context to exceptions

lib/rollbar/configuration.rb

@@ -17,6 +17,7 @@ class Configuration
     attr_accessor :disable_monkey_patch
     attr_accessor :disable_rack_monkey_patch
     attr_accessor :disable_core_monkey_patch
+    attr_accessor :enable_error_context
     attr_accessor :dj_threshold
     attr_accessor :enabled
     attr_accessor :endpoint
@@ -88,6 +89,7 @@ def initialize
       @disable_monkey_patch = false
       @disable_core_monkey_patch = false
       @disable_rack_monkey_patch = false
+      @enable_error_context = true
       @dj_threshold = 0
       @enabled = nil # set to true when configure is called
       @endpoint = DEFAULT_ENDPOINT

lib/rollbar/item.rb

@@ -187,13 +187,19 @@ def build_backtrace_body
     end
 
     def build_extra
+      merged_extra = Util.deep_merge(scrub(extra), scrub(error_context))
+
       if custom_data_method? && !Rollbar::Util.method_in_stack(:custom_data, __FILE__)
-        Util.deep_merge(scrub(custom_data), scrub(extra) || {})
+        Util.deep_merge(scrub(custom_data), merged_extra)
       else
-        scrub(extra)
+        merged_extra.empty? ? nil : merged_extra # avoid putting an empty {} in the payload.
       end
     end
 
+    def error_context
+      exception.respond_to?(:rollbar_context) && exception.rollbar_context
+    end
+
     def scrub(data)
       return data unless data.is_a? Hash
 

lib/rollbar/plugins/error_context.rb

@@ -0,0 +1,11 @@
+module RollbarErrorContext
+  attr_accessor :rollbar_context
+end
+
+Rollbar.plugins.define('error_context') do
+  dependency { configuration.enable_error_context }
+
+  execute! do
+    StandardError.send(:include, RollbarErrorContext)
+  end
+end

spec/rollbar/item_spec.rb

@@ -399,6 +399,22 @@
         end
       end
 
+      context 'with error context' do
+        let(:context) do
+          {:key => 'value', :hash => {:inner_key => 'inner_value'}}
+        end
+        it 'should build exception data with a extra data' do
+          exception.rollbar_context = context
+
+          body = payload['data'][:body]
+          trace = body[:trace]
+
+          trace[:exception][:message].should match(/^(undefined local variable or method `bar'|undefined method `bar' on an instance of)/)
+          trace[:extra][:key].should == 'value'
+          trace[:extra][:hash].should == {:inner_key => 'inner_value'}
+        end
+      end
+
       context 'with nested exceptions' do
         let(:crashing_code) do
           proc do