Extract line filtering to Railties.

The line filter parsing added to ActiveSupport::TestCase is only half the story
to enable line filtering. The other half, of adding the patterns to the options,
is done in the Minitest plugin that Railties has.

Thus it makes more sense to have the filter in Railties with the other half and
all the line filtering tests.

Move the filter and extend Active Support in an initializer, so that when users
or `rails/all.rb` require `rails/test_unit/railtie` we can still filter by line.

activesupport/lib/active_support/test_case.rb

@@ -9,7 +9,6 @@
 require 'active_support/testing/constant_lookup'
 require 'active_support/testing/time_helpers'
 require 'active_support/testing/file_fixtures'
-require 'active_support/testing/composite_filter'
 require 'active_support/core_ext/kernel/reporting'
 
 module ActiveSupport
@@ -39,15 +38,6 @@ def test_order=(new_order)
       def test_order
         ActiveSupport.test_order ||= :random
       end
-
-      def run(reporter, options = {})
-        if options[:patterns] && options[:patterns].any? { |p| p =~ /:\d+/ }
-          options[:filter] = \
-            Testing::CompositeFilter.new(self, options[:filter], options[:patterns])
-        end
-
-        super
-      end
     end
 
     alias_method :method_name, :name

railties/lib/rails/test_unit/line_filtering.rb

@@ -0,0 +1,63 @@
+require 'method_source'
+
+module Rails
+  module LineFiltering # :nodoc:
+    def run(reporter, options = {})
+      if options[:patterns] && options[:patterns].any? { |p| p =~ /:\d+/ }
+        options[:filter] = \
+          CompositeFilter.new(self, options[:filter], options[:patterns])
+      end
+
+      super
+    end
+  end
+
+  class CompositeFilter # :nodoc:
+    def initialize(runnable, filter, patterns)
+      @runnable = runnable
+      @filters = [ derive_regexp(filter), *derive_line_filters(patterns) ].compact
+    end
+
+    def ===(method)
+      @filters.any? { |filter| filter === method }
+    end
+
+    private
+      def derive_regexp(filter)
+        filter =~ %r%/(.*)/% ? Regexp.new($1) : filter
+      end
+
+      def derive_line_filters(patterns)
+        patterns.map do |file_and_line|
+          file, line = file_and_line.split(':')
+          Filter.new(@runnable, file, line) if file
+        end
+      end
+  end
+
+  class Filter # :nodoc:
+    def initialize(runnable, file, line)
+      @runnable, @file = runnable, File.expand_path(file)
+      @line = line.to_i if line
+    end
+
+    def ===(method)
+      return unless @runnable.method_defined?(method)
+
+      if @line
+        test_file, test_range = definition_for(@runnable.instance_method(method))
+        test_file == @file && test_range.include?(@line)
+      else
+        @runnable.instance_method(method).source_location.first == @file
+      end
+    end
+
+    private
+      def definition_for(method)
+        file, start_line = method.source_location
+        end_line = method.source.count("\n") + start_line - 1
+
+        return file, start_line..end_line
+      end
+  end
+end

railties/lib/rails/test_unit/railtie.rb

@@ -1,3 +1,5 @@
+require 'rails/test_unit/line_filtering'
+
 if defined?(Rake.application) && Rake.application.top_level_tasks.grep(/^(default$|test(:|$))/).any?
   ENV['RAILS_ENV'] ||= 'test'
 end
@@ -11,6 +13,10 @@ class TestUnitRailtie < Rails::Railtie
       c.integration_tool :test_unit
     end
 
+    initializer "test_unit.line_filtering" do
+      ActiveSupport::TestCase.extend Rails::LineFiltering
+    end
+
     rake_tasks do
       load "rails/test_unit/testing.rake"
     end