Fix TypeError when no config given and wanrn if file unchanged

If no :before nor :after parameter was supplied, Thor now decides
to append the data after the last piece of information within the file.

In addition, a constant Hash with warnings has been added.
If the file is unchanged because the flag value couldn't be found,
Thor now warns the users and briefly explains what happened.

Author: Mateusz Michalski

lib/thor/actions/inject_into_file.rb

@@ -21,9 +21,15 @@ module Actions
     #     gems.split(" ").map{ |gem| "  config.gem :#{gem}" }.join("\n")
     #   end
     #
+    WARNINGS = { unchanged_no_flag: 'File unchanged! The supplied flag value not found!' }
+
     def insert_into_file(destination, *args, &block)
       data = block_given? ? block : args.shift
       config = args.shift
+
+      config =
+        (config || {}).merge!(after: /\z/) unless config&.key?(:before) || config&.key?(:after)
+
       action InjectIntoFile.new(self, destination, data, config)
     end
     alias_method :inject_into_file, :insert_into_file
@@ -45,16 +51,18 @@ def initialize(base, destination, data, config)
       end
 
       def invoke!
-        say_status :invoke
-
         content = if @behavior == :after
           '\0' + replacement
         else
           replacement + '\0'
         end
 
         if exists?
-          replace!(/#{flag}/, content, config[:force])
+          if replace!(/#{flag}/, content, config[:force])
+            say_status(:invoke)
+          else
+            say_status(:unchanged, warning: WARNINGS[:unchanged_no_flag], color: :red)
+          end
         else
           unless pretend?
             raise Thor::Error, "The file #{ destination } does not appear to exist"
@@ -78,7 +86,7 @@ def revoke!
 
     protected
 
-      def say_status(behavior)
+      def say_status(behavior, warning: nil, color: nil)
         status = if behavior == :invoke
           if flag == /\A/
             :prepend
@@ -87,11 +95,13 @@ def say_status(behavior)
           else
             :insert
           end
+        elsif warning
+          warning
         else
           :subtract
         end
 
-        super(status, config[:verbose])
+        super(status, (color || config[:verbose]))
       end
 
       # Adds the content to the file.
@@ -100,8 +110,10 @@ def replace!(regexp, string, force)
         return if pretend?
         content = File.read(destination)
         if force || !content.include?(replacement)
-          content.gsub!(regexp, string)
+          success = content.gsub!(regexp, string)
+
           File.open(destination, "wb") { |file| file.write(content) }
+          success
         end
       end
     end

spec/actions/inject_into_file_spec.rb

@@ -39,6 +39,17 @@ def file
       expect(File.read(file)).to eq("__start__\nREADME\nmore content\n__end__\n")
     end
 
+    it "appends content to the file if before and after arguments not provided" do
+      invoke!("doc/README", "more content\n")
+      expect(File.read(file)).to eq("__start__\nREADME\n__end__\nmore content\n")
+    end
+
+    it "does not change the file and logs the warning if flag not found in the file" do
+      expect(invoke!("doc/README", "more content\n", after: "whatever")).to(
+        eq("#{Thor::Actions::WARNINGS[:unchanged_no_flag]}  doc/README\n")
+      )
+    end
+
     it "accepts data as a block" do
       invoke! "doc/README", :before => "__end__" do
         "more content\n"