1 files changed, 84 insertions, 0 deletions
diff --git a/rubocop/cop/gettext/static_identifier.rb b/rubocop/cop/gettext/static_identifier.rb
new file mode 100644
index 00000000000..9ca1c88f4b6
--- /dev/null
+++ b/rubocop/cop/gettext/static_identifier.rb
@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Gettext
+      # Ensure that gettext identifiers are statically defined and not
+      # interpolated, formatted, or concatenated.
+      #
+      # @example
+      #
+      #   # bad
+      #   _('Hi #{name}')
+      #   _('Hi %{name}' % { name: 'Luki' })
+      #   _(format('Hi %{name}', name: 'Luki'))
+      #
+      #   # good
+      #   _('Hi %{name}') % { name: 'Luki' }
+      #   format(_('Hi %{name}', name: 'Luki'))
+      #
+      #   # also good
+      #   var = "Hi"
+      #   _(var)
+      #   _(some_method_call)
+      #   _(CONST)
+      class StaticIdentifier < RuboCop::Cop::Base
+        MSG = 'Ensure to pass static strings to translation method `%{method_name}(...)`.'
+
+        # Number of parameters to check for translation methods.
+        PARAMETERS_TO_CHECK = {
+          _: 1,
+          s_: 1,
+          N_: 1,
+          n_: 2
+        }.freeze
+
+        # RuboCop-specific optimization for `on_send`.
+        RESTRICT_ON_SEND = PARAMETERS_TO_CHECK.keys.freeze
+
+        DENIED_METHOD_CALLS = %i[% format + concat].freeze
+
+        def on_send(node)
+          method_name = node.method_name
+          arguments = node.arguments
+
+          each_invalid_argument(method_name, arguments) do |argument_node|
+            message = format(MSG, method_name: method_name)
+
+            add_offense(argument_node || node, message: message)
+          end
+        end
+
+        private
+
+        def each_invalid_argument(method_name, argument_nodes)
+          number = PARAMETERS_TO_CHECK.fetch(method_name)
+
+          argument_nodes.take(number).each do |argument_node|
+            yield argument_node unless valid_argument?(argument_node)
+          end
+        end
+
+        def valid_argument?(node)
+          return false unless node
+
+          basic_type?(node) || multiline_string?(node) || allowed_method_call?(node)
+        end
+
+        def basic_type?(node)
+          node.str_type? || node.lvar_type? || node.const_type?
+        end
+
+        def multiline_string?(node)
+          node.dstr_type? && node.children.all?(&:str_type?)
+        end
+
+        def allowed_method_call?(node)
+          return false unless node.send_type?
+
+          !DENIED_METHOD_CALLS.include?(node.method_name) # rubocop:disable Rails/NegateInclude
+        end
+      end
+    end
+  end
+end