1 files changed, 141 insertions, 0 deletions
diff --git a/lib/gitlab/po_linter.rb b/lib/gitlab/po_linter.rb
new file mode 100644
index 00000000000..abf048815a1
--- /dev/null
+++ b/lib/gitlab/po_linter.rb
@@ -0,0 +1,141 @@
+require 'simple_po_parser'
+
+module Gitlab
+  class PoLinter
+    attr_reader :po_path, :entries, :locale
+
+    VARIABLE_REGEX = /%{\w*}|%[a-z]/.freeze
+
+    def initialize(po_path, locale = 'en')
+      @po_path = po_path
+      @locale = locale
+    end
+
+    def errors
+      @errors ||= validate_po
+    end
+
+    def validate_po
+      if parse_error = parse_po
+        return 'PO-syntax errors' => [parse_error]
+      end
+
+      validate_entries
+    end
+
+    def parse_po
+      @entries = SimplePoParser.parse(po_path)
+      nil
+    rescue SimplePoParser::ParserError => e
+      @entries = []
+      e.message
+    end
+
+    def validate_entries
+      errors = {}
+
+      entries.each do |entry|
+        # Skip validation of metadata
+        next if entry[:msgid].empty?
+
+        errors_for_entry = errors_for_entry(entry)
+        errors[join_message(entry[:msgid])] = errors_for_entry if errors_for_entry.any?
+      end
+
+      errors
+    end
+
+    def errors_for_entry(entry)
+      errors = []
+
+      validate_flags(errors, entry)
+      validate_variables(errors, entry)
+
+      errors
+    end
+
+    def validate_variables(errors, entry)
+      if entry[:msgid_plural].present?
+        validate_variables_in_message(errors, entry[:msgid], entry['msgstr[0]'])
+        validate_variables_in_message(errors, entry[:msgid_plural], entry['msgstr[1]'])
+      else
+        validate_variables_in_message(errors, entry[:msgid], entry[:msgstr])
+      end
+    end
+
+    def validate_variables_in_message(errors, message_id, message_translation)
+      # An empty translation is fine, we fall back to English
+      return unless message_translation.present?
+
+      message_id = join_message(message_id)
+      message_translation = join_message(message_translation)
+
+      used_variables = message_id.scan(VARIABLE_REGEX)
+
+      validate_unnamed_variables(errors, used_variables)
+
+      return if message_translation.empty?
+
+      validate_variable_usage(errors, message_translation, used_variables)
+      validate_translation(errors, message_id, used_variables)
+    end
+
+    def validate_translation(errors, message_id, used_variables)
+      variables = fill_in_variables(used_variables)
+      Gitlab::I18n.with_locale(locale) do
+        translated = message_id.include?('|') ? s_(message_id) : _(message_id)
+        translated % variables
+      end
+    rescue => e
+      errors << "Failure translating to #{locale} with #{variables}: #{e.message}"
+    end
+
+    def fill_in_variables(variables)
+      if variables.empty?
+        []
+      elsif variables.any? { |variable| unnamed_variable?(variable) }
+        variables.map { |variable| variable == '%d' ? Random.rand : SecureRandom.hex }
+      else
+        variables.inject({}) do |hash, variable|
+          variable_name = variable.match(/[^%{].*[^}]/).to_s
+          hash[variable_name] = SecureRandom.hex
+          hash
+        end
+      end
+    end
+
+    def validate_unnamed_variables(errors, variables)
+      if variables.any? { |variable_name| unnamed_variable?(variable_name) } && variables.size > 1
+        errors << 'is combining multiple unnamed variables'
+      end
+    end
+
+    def validate_variable_usage(errors, translation, required_variables)
+      found_variables = translation.scan(VARIABLE_REGEX)
+
+      missing_variables = required_variables - found_variables
+      if missing_variables.any?
+        errors << "<#{translation}> is missing: [#{missing_variables.to_sentence}]"
+      end
+
+      unknown_variables = found_variables - required_variables
+      if unknown_variables.any?
+        errors << "<#{translation}> is using unknown variables: [#{unknown_variables.to_sentence}]"
+      end
+    end
+
+    def unnamed_variable?(variable_name)
+      !variable_name.start_with?('%{')
+    end
+
+    def validate_flags(errors, entry)
+      if flag = entry[:flag]
+        errors << "is marked #{flag}"
+      end
+    end
+
+    def join_message(message)
+      Array(message).join
+    end
+  end
+end