alternative approach

lib/bundle/commands/add.rb

@@ -12,20 +12,20 @@ def run(*args, global: false, file: nil)
         name = args.first # only support one formula at a time for now
         options = {} # we don't currently support passing options
 
-        # read the relevant Brewfile
-        parsed_entries = Bundle::Dsl.new(Brewfile.read(global: global, file: file)).entries
+        # parse the relevant Brewfile
+        dsl = Bundle::Dsl.new(Brewfile.read(global: global, file: file))
 
         # check each of the entries in the specified Brewfile
-        parsed_entries.each do |entry|
+        dsl.entries.each do |entry|
           # raise an error if the entry already exists in the Brewfile
           # this could also be a noop, or print a friendly message
           opoo "'#{name}' already exists in Brewfile."
           raise RuntimeError if entry.name == name
         end
 
-        # need some help / pointers here
-        # is it possible to use Bundle::Dsl to create an in memory representation
-        # of the brewfile that we read, add an entry and then dump that back to the file?
+        dsl.brew(name, options)
+        # execute brew bundle
+        # execute brew bundle dump
       end
     end
   end