Allow passing caller trace into Metadata to support extensions

- Closes rspec#198.

lib/rspec/core/metadata.rb

@@ -32,7 +32,7 @@ def process(*args)
         self[:example_group][:full_description] = full_description_from(*args)
 
         self[:example_group][:block] = user_metadata.delete(:example_group_block)
-        self[:example_group][:file_path], self[:example_group][:line_number] = file_and_line_number_from(caller)
+        self[:example_group][:file_path], self[:example_group][:line_number] = file_and_line_number_from(user_metadata.delete(:caller) || caller)
         self[:example_group][:location] = location_from(self[:example_group])
 
         update(user_metadata)
@@ -68,7 +68,7 @@ def configure_for_example(description, options)
         store(:description, description.to_s)
         store(:full_description, "#{self[:example_group][:full_description]} #{self[:description]}")
         store(:execution_result, {})
-        self[:file_path], self[:line_number] = file_and_line_number_from(caller)
+        self[:file_path], self[:line_number] = file_and_line_number_from(options.delete(:caller) || caller)
         self[:location] = location_from(self)
         update(options)
       end

spec/rspec/core/metadata_spec.rb

@@ -13,6 +13,12 @@ module Core
             end.to raise_error(/:#{key} is not allowed/)
           end
         end
+
+        it "uses :caller if passed as part of the user metadata" do
+          m = Metadata.new
+          m.process('group', :caller => ['example_file:42'])
+          m[:example_group][:location].should == 'example_file:42'
+        end
       end
 
       describe "description" do
@@ -199,6 +205,11 @@ module Core
         it "extracts location from caller" do
           mfe[:location].should == "#{__FILE__}:#{line_number}"
         end
+
+        it "uses :caller if passed as an option" do
+          example_metadata = metadata.for_example('example description', {:caller => ['example_file:42']})
+          example_metadata[:location].should == 'example_file:42'
+        end
 
         it "merges arbitrary options" do
           mfe[:arbitrary].should == :options