Improve perf of metadata-based shared group inclusion.

The call to `RSpec::CallerFilter.first_non_rspec_line`
took most of the time. I originally planned to leverage
rspec/rspec-support#155 but realized we could avoid
calling that entirely by re-using the location from
the group’s metadata.

I re-ran all the benchmarks and updated them. They
look much, much better.

Author: myronmarston

benchmarks/singleton_example_groups/with_config_hooks.rb

@@ -10,20 +10,19 @@
 BenchmarkHelpers.run_benchmarks
 
 __END__
-
 No match -- without singleton group support
-                        614.535  (±33.8%) i/s -      2.520k
+                        575.250  (±29.0%) i/s -      2.484k
 No match -- with singleton group support
-                        555.190  (±21.1%) i/s -      2.496k
+                        503.671  (±21.8%) i/s -      2.250k
 Example match -- without singleton group support
-                        574.821  (±31.5%) i/s -      2.491k
+                        544.191  (±25.7%) i/s -      2.160k
 Example match -- with singleton group support
-                        436.391  (±25.2%) i/s -      1.872k
+                        413.538  (±22.2%) i/s -      1.715k
 Group match -- without singleton group support
-                        544.063  (±31.4%) i/s -      2.112k
+                        517.998  (±28.2%) i/s -      2.058k
 Group match -- with singleton group support
-                        457.098  (±18.8%) i/s -      1.961k
+                        431.554  (±15.3%) i/s -      1.960k
 Both match -- without singleton group support
-                        554.004  (±30.1%) i/s -      2.255k
+                        525.306  (±25.1%) i/s -      2.107k in   5.556760s
 Both match -- with singleton group support
-                        452.834  (±19.7%) i/s -      1.935k
+                        440.288  (±16.6%) i/s -      1.848k

benchmarks/singleton_example_groups/with_config_hooks_module_inclusions_and_shared_context_inclusions.rb

@@ -18,18 +18,18 @@
 __END__
 
 No match -- without singleton group support
-                        452.015  (±33.8%) i/s -      1.900k
+                        544.396  (±34.0%) i/s -      2.340k
 No match -- with singleton group support
-                        464.520  (±31.0%) i/s -      1.887k
+                        451.635  (±31.0%) i/s -      1.935k
 Example match -- without singleton group support
-                        476.961  (±34.6%) i/s -      1.978k in   5.340615s
+                        538.788  (±23.8%) i/s -      2.450k
 Example match -- with singleton group support
-                         76.177  (±34.1%) i/s -    266.000
+                        342.990  (±22.4%) i/s -      1.440k
 Group match -- without singleton group support
-                        364.554  (±28.3%) i/s -      1.372k
+                        509.969  (±26.7%) i/s -      2.070k
 Group match -- with singleton group support
-                        281.761  (±24.1%) i/s -      1.200k
+                        405.284  (±20.5%) i/s -      1.518k
 Both match -- without singleton group support
-                        281.521  (±27.4%) i/s -      1.188k
+                        513.344  (±24.0%) i/s -      1.927k
 Both match -- with singleton group support
-                        297.886  (±18.1%) i/s -      1.288k
+                        406.111  (±18.5%) i/s -      1.760k

benchmarks/singleton_example_groups/with_module_inclusions.rb

@@ -11,18 +11,18 @@
 __END__
 
 No match -- without singleton group support
-                        519.880  (±33.9%) i/s -      2.162k
+                        555.498  (±27.0%) i/s -      2.496k
 No match -- with singleton group support
-                        481.334  (±28.5%) i/s -      2.028k
+                        529.826  (±23.0%) i/s -      2.397k in   5.402305s
 Example match -- without singleton group support
-                        491.348  (±29.9%) i/s -      2.068k
+                        541.845  (±29.0%) i/s -      2.208k
 Example match -- with singleton group support
-                        407.257  (±22.3%) i/s -      1.782k
+                        465.440  (±20.4%) i/s -      2.091k
 Group match -- without singleton group support
-                        483.403  (±36.4%) i/s -      1.815k
+                        530.976  (±24.1%) i/s -      2.303k
 Group match -- with singleton group support
-                        424.932  (±29.4%) i/s -      1.804k
+                        505.291  (±18.8%) i/s -      2.226k
 Both match -- without singleton group support
-                        397.831  (±31.9%) i/s -      1.720k
+                        542.168  (±28.4%) i/s -      2.067k in   5.414905s
 Both match -- with singleton group support
-                        424.233  (±25.5%) i/s -      1.720k
+                        503.226  (±27.2%) i/s -      1.880k in   5.621210s

benchmarks/singleton_example_groups/with_no_config_hooks_or_inclusions.rb

@@ -5,18 +5,18 @@
 __END__
 
 No match -- without singleton group support
-                        504.865  (±31.9%) i/s -      2.128k
+                        565.198  (±28.8%) i/s -      2.438k
 No match -- with singleton group support
-                        463.115  (±26.6%) i/s -      1.998k
+                        539.781  (±18.9%) i/s -      2.496k
 Example match -- without singleton group support
-                        472.825  (±31.9%) i/s -      1.938k
+                        539.287  (±28.2%) i/s -      2.450k in   5.555471s
 Example match -- with singleton group support
-                        436.539  (±33.9%) i/s -      1.840k
+                        511.576  (±28.1%) i/s -      2.058k
 Group match -- without singleton group support
-                        460.643  (±33.4%) i/s -      1.892k
+                        535.298  (±23.2%) i/s -      2.352k
 Group match -- with singleton group support
-                        430.339  (±23.2%) i/s -      1.911k
+                        539.454  (±19.1%) i/s -      2.350k
 Both match -- without singleton group support
-                        406.712  (±26.6%) i/s -      1.848k
+                        550.932  (±32.1%) i/s -      2.145k in   5.930432s
 Both match -- with singleton group support
-                        470.299  (±26.4%) i/s -      1.890k
+                        540.183  (±19.6%) i/s -      2.300k

benchmarks/singleton_example_groups/with_shared_context_inclusions.rb

@@ -11,18 +11,18 @@
 __END__
 
 No match -- without singleton group support
-                        503.700  (±33.2%) i/s -      2.184k
+                        563.304  (±29.6%) i/s -      2.385k
 No match -- with singleton group support
-                        471.018  (±26.8%) i/s -      2.009k
+                        538.738  (±22.3%) i/s -      2.209k
 Example match -- without singleton group support
-                        467.859  (±34.8%) i/s -      2.021k in   5.600106s
+                        546.605  (±25.6%) i/s -      2.450k
 Example match -- with singleton group support
-                         84.138  (±34.5%) i/s -    296.000  in   5.515586s
+                        421.111  (±23.5%) i/s -      1.845k
 Group match -- without singleton group support
-                        384.144  (±27.9%) i/s -      1.560k
+                        536.267  (±27.4%) i/s -      2.050k
 Group match -- with singleton group support
-                        349.301  (±27.5%) i/s -      1.288k
+                        508.644  (±17.7%) i/s -      2.268k
 Both match -- without singleton group support
-                        388.100  (±25.8%) i/s -      1.702k
+                        538.047  (±27.7%) i/s -      2.067k in   5.431649s
 Both match -- with singleton group support
-                        339.310  (±20.3%) i/s -      1.504k
+                        505.388  (±26.7%) i/s -      1.880k in   5.578614s

lib/rspec/core/configuration.rb

@@ -1158,8 +1158,12 @@ def configure_group_with(group, module_list, application_method)
       # Used internally to extend the singleton class of a single example's
       # example group instance with modules using `include` and/or `extend`.
       def configure_example(example)
-        @include_modules.items_for(example.metadata).each do |mod|
-          safe_include(mod, example.example_group_instance.singleton_class)
+        # We replace the metadata so that SharedExampleGroupModule#included
+        # has access to the example's metadata[:location].
+        example.example_group_instance.singleton_class.with_replaced_metadata(example.metadata) do
+          @include_modules.items_for(example.metadata).each do |mod|
+            safe_include(mod, example.example_group_instance.singleton_class)
+          end
         end
       end
 

lib/rspec/core/example_group.rb

@@ -45,7 +45,21 @@ def self.idempotently_define_singleton_method(name, &definition)
       # The [Metadata](Metadata) object associated with this group.
       # @see Metadata
       def self.metadata
-        @metadata if defined?(@metadata)
+        @metadata ||= nil
+      end
+
+      # Temporarily replace the provided metadata.
+      # Intended primarily to allow an example group's singleton class
+      # to return the metadata of the example that it exists for. This
+      # is necessary for shared example group inclusion to work properly
+      # with singleton example groups.
+      # @private
+      def self.with_replaced_metadata(meta)
+        orig_metadata = metadata
+        @metadata = meta
+        yield
+      ensure
+        @metadata = orig_metadata
       end
 
       # @private
@@ -333,7 +347,7 @@ def self.find_and_eval_shared(label, name, inclusion_location, *args, &customiza
           raise ArgumentError, "Could not find shared #{label} #{name.inspect}"
         end
 
-        SharedExampleGroupInclusionStackFrame.with_frame(name, inclusion_location) do
+        SharedExampleGroupInclusionStackFrame.with_frame(name, Metadata.relative_path(inclusion_location)) do
           module_exec(*args, &shared_block)
           module_exec(&customization_block) if customization_block
         end

lib/rspec/core/shared_example_group.rb

@@ -20,7 +20,8 @@ def inspect
       # Our definition evaluates the shared group block in the context of the
       # including example group.
       def included(klass)
-        SharedExampleGroupInclusionStackFrame.with_frame(@description, RSpec::CallerFilter.first_non_rspec_line) do
+        inclusion_line = klass.metadata[:location]
+        SharedExampleGroupInclusionStackFrame.with_frame(@description, inclusion_line) do
           klass.class_exec(&@definition)
         end
       end

spec/rspec/core/metadata_spec.rb

@@ -189,7 +189,7 @@ def metadata_for(*args)
 
               expect(meta[:shared_group_inclusion_backtrace]).to match [ an_object_having_attributes(
                 :shared_group_name  => "some shared behavior",
-                :inclusion_location => a_string_including("#{__FILE__}:#{line}")
+                :inclusion_location => a_string_including("#{Metadata.relative_path __FILE__}:#{line}")
               ) ]
             end
           end
@@ -213,7 +213,7 @@ def metadata_for(*args)
 
                 expect(meta[:shared_group_inclusion_backtrace]).to match [ an_object_having_attributes(
                   :shared_group_name  => "some shared behavior",
-                  :inclusion_location => a_string_including("#{__FILE__}:#{line}")
+                  :inclusion_location => a_string_including("#{Metadata.relative_path __FILE__}:#{line}")
                 ) ]
               end
             end
@@ -239,11 +239,11 @@ def metadata_for(*args)
                 expect(meta[:shared_group_inclusion_backtrace]).to match [
                   an_object_having_attributes(
                     :shared_group_name  => "inner",
-                    :inclusion_location => a_string_including("#{__FILE__}:#{inner_line}")
+                    :inclusion_location => a_string_including("#{Metadata.relative_path __FILE__}:#{inner_line}")
                   ),
                   an_object_having_attributes(
                     :shared_group_name  => "outer",
-                    :inclusion_location => a_string_including("#{__FILE__}:#{outer_line}")
+                    :inclusion_location => a_string_including("#{Metadata.relative_path __FILE__}:#{outer_line}")
                   ),
                 ]
               end