Check for command-name collision on assignment [Fixes #450]

lib/pry/command.rb

@@ -182,9 +182,13 @@ class Pry
     # the current scope.
     # @param [String] command_name_match The name of the colliding command.
     # @param [Binding] target The current binding context.
-    def check_for_command_name_collision(command_name_match)
-      if collision_type = target.eval("defined?(#{command_name_match})")
-        output.puts "#{Pry::Helpers::Text.bold('WARNING:')} Command name collision with a #{collision_type}: '#{command_name_match}'\n\n"
+    def check_for_command_name_collision(command_name_match, arg_string)
+      collision_type = target.eval("defined?(#{command_name_match})")
+      collision_type ||= 'local-variable' if arg_string.match(%r{\A\s*[-+*/%&|^]*=})
+
+      if collision_type
+        output.puts "#{Pry::Helpers::Text.bold('WARNING:')} Calling Pry command '#{command_name_match}'," +
+                                                          "which conflicts with a #{collision_type}.\n\n"
       end
     rescue Pry::RescuableException
     end
@@ -229,7 +233,7 @@ class Pry
     def process_line(line)
       command_name, arg_string, captures, args = tokenize(line)
 
-      check_for_command_name_collision(command_name) if Pry.config.collision_warning
+      check_for_command_name_collision(command_name, arg_string) if Pry.config.collision_warning
 
       self.arg_string = arg_string
       self.captures = captures

test/test_command.rb

@@ -300,7 +300,23 @@ describe "Pry::Command" do
       output = StringIO.new
       cmd.new(:target => binding, :output => output).process_line %(frankie mouse)
 
-      output.string.should =~ /Command name collision/
+      output.string.should =~ /command .* conflicts/
+
+      Pry.config.collision_warning = old
+    end
+
+    it 'should spot collision warnings on assignment if configured' do
+      old = Pry.config.collision_warning
+      Pry.config.collision_warning = true
+
+      cmd = @set.command 'frankie' do
+
+      end
+
+      output = StringIO.new
+      cmd.new(:target => binding, :output => output).process_line %(frankie = mouse)
+
+      output.string.should =~ /command .* conflicts/
 
       Pry.config.collision_warning = old
     end