Reject ruby interpolation in externalized stringsbvl-correct-interpolation-i18n

When using ruby interpolation in externalized strings, they can't be
detected. Which means they will never be presented to be translated.

To mix variables into translations we need to use `sprintf`
instead.

Instead of:

    _("Hello #{subject}")

Use:

    _("Hello %{subject}) % { subject: 'world' }

3 files changed, 36 insertions, 0 deletions

diff --git a/rubocop/cop/line_break_around_conditional_block.rb b/rubocop/cop/line_break_around_conditional_block.rb
index 011f2bcf8bf..59fe6e5d98c 100644
--- a/rubocop/cop/line_break_around_conditional_block.rb
+++ b/rubocop/cop/line_break_around_conditional_block.rb
@@ -48,6 +48,8 @@ module RuboCop
       MSG = 'Add a line break around conditional blocks'
 
       def on_if(node)
+        # This cop causes errors in haml files, so let's skip those
+        return if in_haml?(node)
         return if node.single_line?
         return unless node.if? || node.unless?
 
@@ -116,6 +118,10 @@ module RuboCop
       def end_line?(line)
         line =~ /^\s*(end|})/
       end
+
+      def in_haml?(node)
+        node.location.expression.source_buffer.name.end_with?('.haml.rb')
+      end
     end
   end
 end
diff --git a/rubocop/cop/ruby_interpolation_in_translation.rb b/rubocop/cop/ruby_interpolation_in_translation.rb
new file mode 100644
index 00000000000..b9411fcfd6c
--- /dev/null
+++ b/rubocop/cop/ruby_interpolation_in_translation.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    class RubyInterpolationInTranslation < RuboCop::Cop::Cop
+      MSG = "Don't use ruby interpolation \#{} inside translated strings, instead use \%{}"
+
+      TRANSLATION_METHODS = ':_ :s_ :N_ :n_'
+      RUBY_INTERPOLATION_REGEX = /.*\#\{.*\}/
+
+      def_node_matcher :translation_method?, <<~PATTERN
+        (send nil? {#{TRANSLATION_METHODS}} $dstr ...)
+      PATTERN
+
+      def_node_matcher :plural_translation_method?, <<~PATTERN
+        (send nil? :n_ str $dstr ...)
+      PATTERN
+
+      def on_send(node)
+        interpolation = translation_method?(node) || plural_translation_method?(node)
+        return unless interpolation
+
+        interpolation.descendants.each do |possible_violation|
+          add_offense(possible_violation, message: MSG) if possible_violation.type != :str
+        end
+      end
+    end
+  end
+end
diff --git a/rubocop/rubocop.rb b/rubocop/rubocop.rb
index 88c9bbf24f4..eaf421a7235 100644
--- a/rubocop/rubocop.rb
+++ b/rubocop/rubocop.rb
@@ -28,3 +28,4 @@ require_relative 'cop/rspec/env_assignment'
 require_relative 'cop/rspec/factories_in_migration_specs'
 require_relative 'cop/sidekiq_options_queue'
 require_relative 'cop/destroy_all'
+require_relative 'cop/ruby_interpolation_in_translation'