Merge pull request #1019 from rspec/warn_if_pattern_set_after_specs

Warn if pattern is set after spec files loaded

lib/rspec/core/configuration.rb

@@ -121,6 +121,14 @@ def self.add_setting(name, opts={})
       # Load files matching this pattern (default: `'**/*_spec.rb'`)
       add_setting :pattern, :alias_with => :filename_pattern
 
+      def pattern= value
+        if @spec_files_loaded
+          Kernel.warn "WARNING: Configuring `pattern` to #{value} has no effect since RSpec has already loaded the spec files. Called from #{caller.first}"
+        end
+        @pattern = value
+      end
+      alias :filename_pattern= :pattern=
+
       # Report the times for the slowest examples (default: `false`).
       # Use this to specify the number of examples to include in the profile.
       add_setting :profile_examples
@@ -192,6 +200,7 @@ def initialize
         @color = false
         @pattern = '**/*_spec.rb'
         @failure_exit_code = 1
+        @spec_files_loaded = false
 
         @backtrace_cleaner = BacktraceCleaner.new
 
@@ -226,6 +235,7 @@ def force(hash)
 
       # @private
       def reset
+        @spec_files_loaded = false
         @reporter = nil
         @formatters.clear
       end
@@ -846,6 +856,7 @@ def configure_expectation_framework
       # @private
       def load_spec_files
         files_to_run.uniq.each {|f| load File.expand_path(f) }
+        @spec_files_loaded = true
         raise_if_rspec_1_is_loaded
       end
 

spec/rspec/core/configuration_spec.rb

@@ -495,6 +495,22 @@ def specify_consistent_ordering_of_files_to_run
             expect(config.files_to_run).to include("#{dir}/a_bar.rb")
           end
         end
+
+        context "after files have already been loaded" do
+          it 'will warn that it will have no effect' do
+            allow(Kernel).to receive(:warn)
+            config.load_spec_files
+            config.send(setter, "rspec/**/*.spec"); line = __LINE__
+            expect(Kernel).to have_received(:warn).with /has no effect.*#{__FILE__}:#{line}/
+          end
+
+          it 'will not warn if reset is called after load_spec_files' do
+            config.load_spec_files
+            config.reset
+            expect(Kernel).to_not receive(:warn)
+            config.send(setter, "rspec/**/*.spec")
+          end
+        end
       end
     end