Add a function to update / regenerate deprecated shims

In order to move existing unamespaced functions to the stdlib namespace
(#1346) without breaking backwards compatibility, we need some
compatibility shims.  They will all look-like the same, so add a rake
task to regenerate them if we need to update them.

Author: smortex

Rakefile

@@ -88,3 +88,33 @@ EOM
   end
 end
 
+desc 'Regenerate the deprecated unamespaced shims'
+task :regenerate_unamespaced_shims do
+  Dir['lib/puppet/functions/*.rb'].each do |filename|
+    content = File.read(filename)
+
+    unless content =~ /@summary DEPRECATED.  Use the namespaced function/
+      warn("#{filename} does not look like a deprecation shim (skipping)")
+      next
+    end
+
+    function_name = File.basename(filename, '.rb')
+
+    File.write(filename, <<~CODE)
+      # frozen_string_literal: true
+
+      # THIS FILE WAS GENERATED BY `rake regenerate_unamespaced_shims`
+
+      # @summary DEPRECATED.  Use the namespaced function [`stdlib::#{function_name}`](#stdlib#{function_name}) instead.
+      Puppet::Functions.create_function(:#{function_name}) do
+        dispatch :deprecation_gen do
+          repeated_param 'Any', :args
+        end
+        def deprecation_gen(*args)
+          call_function('deprecation', '#{function_name}', 'This method is deprecated, please use stdlib::#{function_name} instead.')
+          call_function('stdlib::#{function_name}', *args)
+        end
+      end
+    CODE
+  end
+end

lib/puppet/functions/has_interface_with.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+# THIS FILE WAS GENERATED BY `rake regenerate_unamespaced_shims`
+
 # @summary DEPRECATED.  Use the namespaced function [`stdlib::has_interface_with`](#stdlibhas_interface_with) instead.
 Puppet::Functions.create_function(:has_interface_with) do
   dispatch :deprecation_gen do